diff --git a/README.md b/README.md
index 6d0ec02..bf0e84f 100644
--- a/README.md
+++ b/README.md
@@ -200,3 +200,17 @@ upper_wavelength_interp_limit: float
     dispersion coefficients are computed over a certain wavelength range. This parameter
     sets the lowest end of this range. If the set value is higher than the higher end of the
     wavelength window, it is lowered down to that point. default : 1900e-9
+
+## Environment parameters
+
+path_prefixes : dict[str, str]
+    key : hostname (as returned by `socket.gethostname()`)
+    value : path to the head's current working directory
+    When running the simulations on multiple instances, the head's working directory needs to be mounted as a network drive on every other node, with its path specified with this parameter
+
+    Example:
+    
+    [environment.path_prefixes]
+    Excellent_node = "Z:\\simulations\\"
+
+    this means that if I'm working on Average_node (i.e. Average_node is the head of the ray cluster) in `/Users/username/simulations/` and connecting Excellent_node (Windows) to the ray cluster, I need to be able to access Average_node's `simulations` directory by mounting it as a network drive. In this example, `username` is shared on the network by Average_node and Excellent_node is mounting it as a network share with the same credentials as Average_node's (to avoid permission problems). This means that `Z:\\simulations\` on Excellent_node points to the same directory as `/Users/username/simulations/` on Average_nodes. Jobs sent by the head's scgenerator module to Excellent_node will have an environment variable set so that Average_node's cwd so that files are all saved in the same place.
\ No newline at end of file
diff --git a/developement_help.md b/developement_help.md
index 9adb5f2..02658e1 100644
--- a/developement_help.md
+++ b/developement_help.md
@@ -1,6 +1,6 @@
 ## add parameter
 - add it to ```const.valid_param_types```
 - add it to README.md
-- add the necessary logic in the appropriate ```initialize.ensure_consistency``` subfunction
+- add the necessary logic in the appropriate ```initialize._ensure_consistency``` subfunction
 - optional : add a default value
-- optional : add to valid varying
+- optional : add to valid_variable
diff --git a/requirements.txt b/requirements.txt
new file mode 100644
index 0000000..31cc1c5
--- /dev/null
+++ b/requirements.txt
@@ -0,0 +1,6 @@
+numpy
+matplotlib
+scipy
+ray
+send2trash
+toml
\ No newline at end of file
diff --git a/scgenerator.log b/scgenerator.log
index e69de29..220f36e 100644
--- a/scgenerator.log
+++ b/scgenerator.log
@@ -0,0 +1,31 @@
+scgenerator.initialize: computed initial N = 8.66
+scgenerator.initialize: computed initial N = 8.66
+scgenerator.initialize: computed initial N = 8.66
+scgenerator.initialize: computed initial N = 8.66
+scgenerator.initialize: computed initial N = 8.66
+INFO: scgenerator.initialize: computed initial N = 8.66
+INFO: scgenerator.initialize: computed initial N = 8.66
+INFO: scgenerator.initialize: computed initial N = 8.66
+INFO: scgenerator.initialize: computed initial N = 8.66
+INFO: scgenerator.initialize: computed initial N = 8.66
+INFO: scgenerator.initialize: computed initial N = 8.66
+INFO: scgenerator.initialize: computed initial N = 8.66
+INFO: scgenerator.initialize: computed initial N = 8.66
+INFO: scgenerator.initialize: computed initial N = 8.66
+INFO: scgenerator.initialize: computed initial N = 8.66
+INFO: scgenerator.initialize: computed initial N = 8.66
+INFO: scgenerator.initialize: computed initial N = 8.66
+INFO: scgenerator.initialize: computed initial N = 8.66
+INFO: scgenerator.initialize: computed initial N = 8.66
+INFO: scgenerator.initialize: computed initial N = 8.66
+INFO: id 0 wavelength 8.35e-07 num 0: energy conserved
+INFO: id 2 wavelength 8.35e-07 num 2: energy conserved
+INFO: id 3 wavelength 8.35e-07 num 3: energy conserved
+INFO: id 4 wavelength 8.35e-07 num 4: energy conserved
+INFO: id 5 wavelength 8.35e-07 num 5: energy conserved
+INFO: id 9 wavelength 8.35e-07 num 9: energy conserved
+INFO: id 10 wavelength 8.3375e-07 num 0: energy conserved
+INFO: id 14 wavelength 8.3375e-07 num 4: energy conserved
+INFO: id 16 wavelength 8.3375e-07 num 6: energy conserved
+INFO: id 19 wavelength 8.3375e-07 num 9: energy conserved
+INFO: id 21 wavelength 8.325e-07 num 1: energy conserved
diff --git a/src/scgenerator/__init__.py b/src/scgenerator/__init__.py
index c615544..46e51b1 100644
--- a/src/scgenerator/__init__.py
+++ b/src/scgenerator/__init__.py
@@ -1,5 +1,5 @@
 from .initialize import compute_init_parameters
-from .io import Paths, iter_load_sim_data, load_toml, load_sim_data
+from .io import Paths, load_toml
 from .math import abs2, argclosest, span
 from .physics import fiber, materials, pulse, simulate, units
 from .physics.simulate import RK4IP, new_simulations
diff --git a/src/scgenerator/const.py b/src/scgenerator/const.py
index 847548b..2e85d7f 100644
--- a/src/scgenerator/const.py
+++ b/src/scgenerator/const.py
@@ -11,6 +11,11 @@ def integer(n):
     return isinstance(n, int) and n > 0
 
 
+def generic_dict(d):
+    """must be a dictionary"""
+    return isinstance(d, dict)
+
+
 def boolean(b):
     """must be a boolean"""
     return type(b) == bool
@@ -146,6 +151,9 @@ valid_param_types = dict(
         upper_wavelength_interp_limit=num,
         frep=num,
     ),
+    environment=dict(
+        path_prefixes=generic_dict,
+    ),
 )
 
 hc_model_specific_parameters = dict(
@@ -163,7 +171,7 @@ hc_model_specific_parameters = dict(
 )
 """dependecy map only includes actual fiber parameters and exclude gas parameters"""
 
-valid_varying = dict(
+valid_variable = dict(
     fiber=[
         "beta",
         "gamma",
@@ -190,8 +198,10 @@ valid_varying = dict(
         "soliton_num",
     ],
     simulation=["behaviors", "raman_type", "tolerated_error", "step_size", "ideal_gas"],
+    environment=[],
 )
 
-
-TMP_FOLDER_KEY_BASE = "SCGENERATOR_TMP"
+ENVIRON_KEY_BASE = "SCGENERATOR_"
+TMP_FOLDER_KEY_BASE = ENVIRON_KEY_BASE + "TMP_"
+PREFIX_KEY_BASE = ENVIRON_KEY_BASE + "PREFIX_"
 PARAM_SEPARATOR = " "
diff --git a/src/scgenerator/defaults.py b/src/scgenerator/defaults.py
index 586d120..0197e55 100644
--- a/src/scgenerator/defaults.py
+++ b/src/scgenerator/defaults.py
@@ -82,7 +82,7 @@ def get(section_dict, param, **kwargs):
 
     # whether the parameter is in the right place and valid is checked elsewhere,
     # here, we just make sure it is present.
-    if param not in section_dict and param not in section_dict.get("varying", {}):
+    if param not in section_dict and param not in section_dict.get("variable", {}):
         try:
             section_dict[param] = default_parameters[param]
             # LOG
diff --git a/src/scgenerator/initialize.py b/src/scgenerator/initialize.py
index 033fd9c..84aff92 100644
--- a/src/scgenerator/initialize.py
+++ b/src/scgenerator/initialize.py
@@ -1,15 +1,17 @@
 import os
-from typing import Any, Iterator, List, Mapping, Tuple
+from collections.abc import Mapping
+from typing import Any, Iterator, List, Tuple
+
 import numpy as np
 from numpy import pi
 
 from . import defaults, io, utils
-from .math import length, power_fact
-from .physics import fiber, pulse, units
-from .const import valid_param_types, valid_varying, hc_model_specific_parameters
+from .const import hc_model_specific_parameters, valid_param_types, valid_variable
 from .errors import *
 from .logger import get_logger
-from .utils import varying_iterator, count_variations
+from .math import length, power_fact
+from .physics import fiber, pulse, units
+from .utils import count_variations, variable_iterator
 
 
 class ParamSequence(Mapping):
@@ -17,16 +19,32 @@ class ParamSequence(Mapping):
         self.config = validate(config)
         self.name = self.config["name"]
 
-        self.num_sim, self.num_varying = count_variations(self.config)
+        self.num_sim, self.num_variable = count_variations(self.config)
         self.single_sim = self.num_sim == 1
 
-    def __iter__(self) -> Iterator[Tuple[list, dict]]:
+    def iterate_without_computing(self) -> Iterator[Tuple[List[Tuple[str, Any]], dict]]:
+        """takes the output of `scgenerator.utils.variable_iterator` which is a new dict per different
+        parameter set and iterates through every single necessary simulation
+
+        Yields
+        -------
+        Iterator[Tuple[List[Tuple[str, Any]], dict]]
+            variable_ind : a list of (name, value) tuple of parameter name and value that are variable. The parameter
+            "num" (how many times this specific parameter set has been yielded already) and "id" (how many parameter sets
+            have been exhausted already) are added to the list to make sure every yielded list is unique.
+        """
+        i = 0  # unique sim id
+        for variable_only, full_config in variable_iterator(self.config):
+            for j in range(self["simulation", "repeat"]):
+                variable_ind = [("id", i)] + variable_only + [("num", j)]
+                i += 1
+                yield variable_ind, full_config
+
+    def __iter__(self) -> Iterator[Tuple[List[Tuple[str, Any]], dict]]:
         """iterates through all possible parameters, yielding a config as welle as a flattened
         computed parameters set each time"""
-        for varying_only, full_config in varying_iterator(self.config):
-            for i in range(self["simulation", "repeat"]):
-                varying = varying_only + [("num", i)]
-                yield varying, compute_init_parameters(full_config)
+        for variable_list, full_config in self.iterate_without_computing():
+            yield variable_list, compute_init_parameters(full_config)
 
     def __len__(self):
         return self.num_sim
@@ -47,24 +65,34 @@ class RecoveryParamSequence(ParamSequence):
                 self.num_sim -= 1
         self.single_sim = self.num_sim == 1
 
-    def __iter__(self) -> Iterator[Tuple[list, dict]]:
-        for varying_only, full_config in varying_iterator(self.config):
-            for i in range(self["simulation", "repeat"]):
-                varying = varying_only + [("num", i)]
-                print("varying ", varying_only, i)
-                sub_folder = os.path.join(
-                    io.get_data_folder(self.id), utils.format_varying_list(varying)
-                )
+    def __iter__(self) -> Iterator[Tuple[List[Tuple[str, Any]], dict]]:
+        for variable_list, full_config in self.iterate_without_computing():
 
-                if not io.propagation_initiated(sub_folder):
-                    yield varying, compute_init_parameters(full_config)
-                elif not io.propagation_completed(sub_folder, self.config["simulation"]["z_num"]):
-                    yield varying, recover_params(full_config, varying, self.id)
-                else:
-                    continue
+            sub_folder = os.path.join(
+                io.get_data_folder(self.id), utils.format_variable_list(variable_list)
+            )
+
+            if not io.propagation_initiated(sub_folder):
+                yield variable_list, compute_init_parameters(full_config)
+            elif not io.propagation_completed(sub_folder, self.config["simulation"]["z_num"]):
+                yield variable_list, recover_params(full_config, variable_list, self.id)
+            else:
+                continue
 
 
 def validate(config: dict) -> dict:
+    """validates a configuration dictionary and attempts to fill in defaults
+
+    Parameters
+    ----------
+    config : dict
+        loaded configuration
+
+    Returns
+    -------
+    dict
+        updated configuration
+    """
     _validate_types(config)
     return _ensure_consistency(config)
 
@@ -165,7 +193,7 @@ def _validate_types(config):
     for domain, parameters in config.items():
         if isinstance(parameters, dict):
             for param_name, param_value in parameters.items():
-                if param_name == "varying":
+                if param_name == "variable":
                     for k_vary, v_vary in param_value.items():
                         if not isinstance(v_vary, list):
                             raise TypeError(f"Varying parameters should be specified in a list")
@@ -175,7 +203,7 @@ def _validate_types(config):
                                 f"Varying parameters lists should contain at least 1 element"
                             )
 
-                        if k_vary not in valid_varying[domain]:
+                        if k_vary not in valid_variable[domain]:
                             raise TypeError(f"'{k_vary}' is not a valid variable parameter")
 
                         [
@@ -189,7 +217,7 @@ def _validate_types(config):
 
 
 def _contains(sub_conf, param):
-    return param in sub_conf or param in sub_conf.get("varying", {})
+    return param in sub_conf or param in sub_conf.get("variable", {})
 
 
 def _ensure_consistency_fiber(fiber):
@@ -330,8 +358,8 @@ def _ensure_consistency_simulation(simulation):
     ]:
         simulation = defaults.get(simulation, param)
 
-    if "raman" in simulation["behaviors"] or any(
-        ["raman" in l for l in simulation.get("varying", {}).get("behaviors", [])]
+    if "raman" in simulation.get("behaviors", {}) or any(
+        ["raman" in l for l in simulation.get("variable", {}).get("behaviors", [])]
     ):
         simulation = defaults.get(simulation, "raman_type", specified_parameters=["raman"])
     return simulation
@@ -359,7 +387,7 @@ def _ensure_consistency(config):
         for param_name in sub_dict:
             for set_param in config.values():
                 if isinstance(set_param, dict):
-                    if param_name in set_param and param_name in set_param.get("varying", {}):
+                    if param_name in set_param and param_name in set_param.get("variable", {}):
                         raise DuplicateParameterError(
                             f"got multiple values for parameter '{param_name}'"
                         )
@@ -377,10 +405,9 @@ def _ensure_consistency(config):
     return config
 
 
-def recover_params(params: dict, varying_only: List[Tuple[str, Any]], task_id: int):
-    print("RECOVERING PARAMETERS")
+def recover_params(params: dict, variable_only: List[Tuple[str, Any]], task_id: int):
     params = compute_init_parameters(params)
-    vary_str = utils.format_varying_list(varying_only)
+    vary_str = utils.format_variable_list(variable_only)
     path = os.path.join(io.get_data_folder(task_id), vary_str)
     num, last_spectrum = io.load_last_spectrum(path)
     params["spec_0"] = last_spectrum
@@ -396,7 +423,7 @@ def compute_init_parameters(config):
     Parameters
     ----------
     config : dict
-        a configuration dictionary containing the pulse, fiber and simulation sections with no varying parameter.
+        a configuration dictionary containing the pulse, fiber and simulation sections with no variable parameter.
         a flattened parameters dictionary may be provided instead
         Note : checking the validity of the configuration shall be done before calling this function.
 
diff --git a/src/scgenerator/io.py b/src/scgenerator/io.py
index a155c1b..3b23f3c 100644
--- a/src/scgenerator/io.py
+++ b/src/scgenerator/io.py
@@ -1,4 +1,3 @@
-import json
 import os
 import shutil
 from datetime import datetime
@@ -11,29 +10,11 @@ import toml
 from send2trash import TrashPermissionError, send2trash
 
 from . import utils
-from .const import TMP_FOLDER_KEY_BASE, PARAM_SEPARATOR
+from .const import PARAM_SEPARATOR, PREFIX_KEY_BASE, TMP_FOLDER_KEY_BASE, ENVIRON_KEY_BASE
 from .errors import IncompleteDataFolderError
 from .logger import get_logger
 
 
-def load_toml(path: str):
-    """returns a dictionary parsed from the specified toml file"""
-    if not path.lower().endswith(".toml"):
-        path += ".toml"
-    with open(path, mode="r") as file:
-        dico = toml.load(file)
-    return dico
-
-
-def save_toml(path, dico):
-    """saves a dictionary into a toml file"""
-    if not path.lower().endswith(".toml"):
-        path += ".toml"
-    with open(path, mode="w") as file:
-        toml.dump(dico, file)
-    return dico
-
-
 class Paths:
     home = os.path.expanduser("~")
     _data_files = ["silica.toml", "gas.toml", "hr_t.npz"]
@@ -48,13 +29,15 @@ class Paths:
     @classmethod
     def get(cls, key):
         if key not in cls.paths:
-            if os.path.exists("paths.json"):
-                with open("paths.json") as file:
-                    paths_dico = json.load(file)
+            if os.path.exists("paths.toml"):
+                with open("paths.toml") as file:
+                    paths_dico = toml.load(file)
                 for k, v in paths_dico.items():
-                    cls.paths[k] = os.path.abspath(os.path.expanduser(v))
+                    cls.paths[k] = v
         if key not in cls.paths:
-            print(f"{key} was not found in path index, returning current working directory.")
+            get_logger(__name__).info(
+                f"{key} was not found in path index, returning current working directory."
+            )
             cls.paths[key] = os.getcwd()
 
         return cls.paths[key]
@@ -80,6 +63,48 @@ class Paths:
         return os.path.join(cls.get("plots"), name)
 
 
+def abspath(rel_path: str):
+    """returns the complete path with the correct root. In other words, allows to modify absolute paths
+    in case the process accessing this function is a sub-process started from another device.
+
+    Parameters
+    ----------
+    rel_path : str
+        relative path
+
+    Returns
+    -------
+    str
+        absolute path
+    """
+    key = utils.formatted_hostname()
+    prefix = os.getenv(key)
+    if prefix is None:
+        p = os.path.abspath(rel_path)
+    else:
+        p = os.path.join(prefix, rel_path)
+
+    return os.path.normpath(p)
+
+
+def load_toml(path: str):
+    """returns a dictionary parsed from the specified toml file"""
+    if not path.lower().endswith(".toml"):
+        path += ".toml"
+    with open(abspath(path), mode="r") as file:
+        dico = toml.load(file)
+    return dico
+
+
+def save_toml(path, dico):
+    """saves a dictionary into a toml file"""
+    if not path.lower().endswith(".toml"):
+        path += ".toml"
+    with open(abspath(path), mode="w") as file:
+        toml.dump(dico, file)
+    return dico
+
+
 def serializable(val):
     """returns True if val is serializable into a Json file"""
     types = (np.ndarray, float, int, str, list, tuple)
@@ -132,6 +157,7 @@ def save_parameters(param_dict, file_name="param"):
     folder_name, file_name = os.path.split(file_name)
     folder_name = "tmp" if folder_name == "" else folder_name
     file_name = os.path.splitext(file_name)[0]
+    folder_name = abspath(folder_name)
 
     if not os.path.exists(folder_name):
         os.makedirs(folder_name)
@@ -146,21 +172,23 @@ def save_parameters(param_dict, file_name="param"):
     return os.path.join(folder_name, file_name)
 
 
-def load_previous_parameters(path):
-    """loads a parameters json files and converts data to appropriate type
+def load_previous_parameters(path: str):
+    """loads a parameters toml files and converts data to appropriate type
     Parameters
     ----------
-        path : path-like
-            path to the json
+    path : str
+        path to the toml
+
     Returns
     ----------
-        params : dict
+    dict
+        flattened parameters dictionary
     """
     params = load_toml(path)
+
     for k, v in params.items():
-        if isinstance(v, list):
-            if isinstance(v[0], (float, int)):
-                params[k] = np.array(v)
+        if isinstance(v, list) and isinstance(v[0], (float, int)):
+            params[k] = np.array(v)
     return params
 
 
@@ -180,101 +208,32 @@ def load_material_dico(name):
         return toml.loads(Paths.gets("gas"))[name]
 
 
-def load_sim_data(folder_name, ind=None, load_param=True):
-    """
-    loads the data already simulated.
-    defauft shape is (z_targets, n, nt)
+def set_environ(config: dict):
+    """sets environment variables specified in the config
 
     Parameters
     ----------
-        folder_name : (string) folder where the simulation data is stored
-        ind : list of indices if only certain spectra are desired.
-                - If left to None, returns every spectrum
-                - If only 1 int, will cast the (1, n, nt) array into a (n, nt) array
-        load_param : (bool) return the parameter dictionary as well. returns None
-                if not available
-    Returns
-    ----------
-        spectra : array
-            squeezed array of complex spectra (n simulation on a nt size grid at each ind)
-    Raises
-    ----------
-        FileNotFoundError : folder does not exist or does not contain sufficient
-                            data
+    config : dict
+        whole simulation config file
     """
-
-    print(f"opening {folder_name}")
-
-    # Check if file exists and assert how many z positions there are
-    if not os.path.exists(folder_name):
-        raise FileNotFoundError(f"Folder {folder_name} does not exist")
-    nmax = len(glob(os.path.join(folder_name, "spectra_*.npy")))
-    if nmax <= 0:
-        raise FileNotFoundError(f"No appropriate file in specified folder {folder_name}")
-
-    if ind is None:
-        ind = range(nmax)
-    elif isinstance(ind, int):
-        ind = [ind]
-
-    # Load the spectra
-    spectra = []
-    for i in ind:
-        spectra.append(load_single_spectrum(folder_name, i))
-    spectra = np.array(spectra)
-
-    # Load the parameters dictionary
-    try:
-        params = load_previous_parameters(os.path.join(folder_name, "params.toml"))
-    except FileNotFoundError:
-        print(f"parameters corresponding to {folder_name} not found")
-        params = None
-
-    print("data successfully loaded")
-    if load_param:
-        return spectra.squeeze(), params
-    else:
-        return spectra.squeeze()
+    environ = config.get("environment", {})
+    for k, v in environ.get("path_prefixes", {}).items():
+        os.environ[(PREFIX_KEY_BASE + k).upper()] = v
 
 
 def get_all_environ() -> Dict[str, str]:
     """returns a dictionary of all environment variables set by any instance of scgenerator"""
-    return dict(filter(lambda el: el[0].startswith(TMP_FOLDER_KEY_BASE), os.environ.items()))
+    d = dict(filter(lambda el: el[0].startswith(ENVIRON_KEY_BASE), os.environ.items()))
+    print(d)
+    return d
 
 
 def load_single_spectrum(folder, index) -> np.ndarray:
-    return np.load(os.path.join(folder, f"spectra_{index}.npy"))
-
-
-def iter_load_sim_data(folder_name, with_params=False) -> Iterable[np.ndarray]:
-    """
-    similar to load_sim_data but works as an iterator
-    """
-
-    if not os.path.exists(folder_name):
-        raise FileNotFoundError(f"Folder {folder_name} does not exist")
-    nmax = len(glob(os.path.join(folder_name, "spectra_*.npy")))
-    if nmax <= 0:
-        raise FileNotFoundError(f"No appropriate file in specified folder {folder_name}")
-
-    params = {}
-    if with_params:
-        try:
-            params = load_previous_parameters(os.path.join(folder_name, "params.toml"))
-        except FileNotFoundError:
-            print(f"parameters corresponding to {folder_name} not found")
-            params = None
-
-    print(f"iterating through {folder_name}")
-    for i in range(nmax):
-        if with_params:
-            yield load_single_spectrum(folder_name, i), params
-        else:
-            yield load_single_spectrum(folder_name, i)
+    return np.load(os.path.join(abspath(folder), f"spectra_{index}.npy"))
 
 
 def get_data_subfolders(path: str) -> List[str]:
-    """returns a list of path/subfolders in the specified directory
+    """returns a list of relative path/subfolders in the specified directory
 
     Parameters
     ----------
@@ -314,7 +273,7 @@ def check_data_integrity(sub_folders: List[str], init_z_num: int):
 
 
 def propagation_initiated(sub_folder) -> bool:
-    if os.path.isdir(sub_folder):
+    if os.path.isdir(abspath(sub_folder)):
         return find_last_spectrum_file(sub_folder) > 0
     return False
 
@@ -388,6 +347,7 @@ def merge_same_simulations(path: str):
     pt = utils.ProgressTracker(num_operations, logger=logger, prefix="merging data : ")
 
     for base_folder in base_folders:
+        logger.debug(f"creating new folder {base_folder}")
         for j in range(z_num):
             spectra = []
             for i in range(repeat):
@@ -396,7 +356,7 @@ def merge_same_simulations(path: str):
                 )
             dest_folder = ensure_folder(base_folder, prevent_overwrite=False)
             spectra = np.array(spectra).reshape(repeat, len(spectra[0]))
-            np.save(os.path.join(dest_folder, f"spectra_{j}.npy"), spectra)
+            np.save(os.path.join(dest_folder, f"spectra_{j}.npy"), spectra.squeeze())
             pt.update()
         for file_name in ["z.npy", "params.toml"]:
             shutil.copy(
@@ -417,7 +377,6 @@ def get_data_folder(task_id: int, name_if_new: str = ""):
     tmp = os.getenv(TMP_FOLDER_KEY_BASE + idstr)
     if tmp is None:
         tmp = ensure_folder("scgenerator_" + name_if_new + idstr)
-        tmp = os.path.abspath(tmp)
         os.environ[TMP_FOLDER_KEY_BASE + idstr] = tmp
     return tmp
 
@@ -453,19 +412,23 @@ def generate_file_path(file_name: str, task_id: int, identifier: str = "") -> st
     str
         the full path
     """
-    base_name, ext = os.path.splitext(file_name)
-    folder = get_data_folder(task_id)
-    folder = os.path.join(folder, identifier)
-    folder = ensure_folder(folder, prevent_overwrite=False)
-    i = 0
-    base_name = os.path.join(folder, base_name)
-    new_name = base_name + ext
-    while os.path.exists(new_name):
-        print(f"{i=}")
-        new_name = f"{base_name}_{i}{ext}"
-        i += 1
+    # base_name, ext = os.path.splitext(file_name)
+    # folder = get_data_folder(task_id)
+    # folder = os.path.join(folder, identifier)
+    # folder = ensure_folder(folder, prevent_overwrite=False)
+    # i = 0
+    # base_name = os.path.join(folder, base_name)
+    # new_name = base_name + ext
+    # while os.path.exists(new_name):
+    #     new_name = f"{base_name}_{i}{ext}"
+    #     i += 1
 
-    return new_name
+    path = os.path.join(get_data_folder(task_id), identifier)
+    path = abspath(path)
+    os.makedirs(path, exist_ok=True)
+    path = os.path.join(path, file_name)
+
+    return path
 
 
 def save_data(data: np.ndarray, file_name: str, task_id: int, identifier: str = ""):
@@ -482,14 +445,17 @@ def save_data(data: np.ndarray, file_name: str, task_id: int, identifier: str =
     identifier : str, optional
         identifier in the main data folder of the task, by default ""
     """
+
     path = generate_file_path(file_name, task_id, identifier)
     np.save(path, data)
+    get_logger(__name__).debug(f"saved data in {path}")
+    return
 
 
 def ensure_folder(name, i=0, suffix="", prevent_overwrite=True):
     """creates a folder for simulation data named name and prevents overwrite
     by adding a suffix if necessary and returning the name"""
-    prefix, last_dir = os.path.split(os.path.abspath(name))
+    prefix, last_dir = os.path.split(abspath(name))
     exploded = [prefix]
     sub_prefix = prefix
     while sub_prefix != os.path.abspath("/"):
diff --git a/src/scgenerator/logger.py b/src/scgenerator/logger.py
index 9e099c6..97169be 100644
--- a/src/scgenerator/logger.py
+++ b/src/scgenerator/logger.py
@@ -1,5 +1,22 @@
 import logging
 
+DEFAULT_LEVEL = logging.INFO
+
+lvl_map = dict(
+    debug=logging.DEBUG,
+    info=logging.INFO,
+    warning=logging.WARNING,
+    error=logging.ERROR,
+    fatal=logging.FATAL,
+    critical=logging.CRITICAL,
+)
+
+loggers = []
+
+
+def _set_debug():
+    DEFAULT_LEVEL = logging.DEBUG
+
 
 def get_logger(name=None):
     """returns a logging.Logger instance. This function is there because if scgenerator
@@ -18,9 +35,20 @@ def get_logger(name=None):
     """
     name = __name__ if name is None else name
     logger = logging.getLogger(name)
+    if name not in loggers:
+        loggers.append(logger)
     return configure_logger(logger)
 
 
+# def set_level_all(lvl):
+#     _default_lvl =
+#     logging.basicConfig(level=lvl_map[lvl])
+#     for logger in loggers:
+#         logger.setLevel(lvl_map[lvl])
+#         for handler in logger.handlers:
+#             handler.setLevel(lvl_map[lvl])
+
+
 def configure_logger(logger, logfile="scgenerator.log"):
     """configures a logging.Logger obj
 
@@ -39,12 +67,14 @@ def configure_logger(logger, logfile="scgenerator.log"):
     if not hasattr(logger, "already_configured"):
         if logfile is not None:
             file_handler = logging.FileHandler("scgenerator.log", "a+")
-            file_handler.setFormatter(logging.Formatter("{name}: {message}", style="{"))
+            file_handler.setFormatter(
+                logging.Formatter("{levelname}: {name}: {message}", style="{")
+            )
             logger.addHandler(file_handler)
 
         stream_handler = logging.StreamHandler()
         logger.addHandler(stream_handler)
-        logger.setLevel(logging.INFO)
+        logger.setLevel(DEFAULT_LEVEL)
 
         logger.already_configured = True
     return logger
\ No newline at end of file
diff --git a/src/scgenerator/physics/fiber.py b/src/scgenerator/physics/fiber.py
index 956f46e..6c03e04 100644
--- a/src/scgenerator/physics/fiber.py
+++ b/src/scgenerator/physics/fiber.py
@@ -272,7 +272,7 @@ def A_eff_hasan(core_radius, capillary_num, capillary_spacing):
 
 
 def HCPCF_find_with_given_ZDW(
-    varying,
+    variable,
     target,
     search_range,
     material_dico,
@@ -286,13 +286,13 @@ def HCPCF_find_with_given_ZDW(
 
     Parameters
     ----------
-    varying : str {"pressure", "temperature"}
+    variable : str {"pressure", "temperature"}
         which parameter to vary
     target : float
         the ZDW target, in m
     search_range : array, shape (2,)
         (min, max) of the search range
-    other parameters : see HCPCF_dispersion. Pressure or temperature is used as initial value if it is varying
+    other parameters : see HCPCF_dispersion. Pressure or temperature is used as initial value if it is variable
 
     Returns
     -------
@@ -304,7 +304,7 @@ def HCPCF_find_with_given_ZDW(
     #
     fixed = [material_dico, model, model_params, ideal]
 
-    if varying == "pressure":
+    if variable == "pressure":
         fixed.append(temperature)
         x0 = 1e5 if pressure is None else pressure
 
@@ -321,7 +321,7 @@ def HCPCF_find_with_given_ZDW(
             out = current_ZDW - target
             return out
 
-    elif varying == "temperature":
+    elif variable == "temperature":
         fixed.append(pressure)
         x0 = 273.15 if temperature is None else temperature
 
@@ -339,7 +339,7 @@ def HCPCF_find_with_given_ZDW(
             return out
 
     else:
-        raise AttributeError(f"'varying' arg must be 'pressure' or 'temperature', not {varying}")
+        raise AttributeError(f"'variable' arg must be 'pressure' or 'temperature', not {variable}")
 
     optimized = optimize.root_scalar(
         zdw, x0=x0, args=tuple(fixed), method="brentq", bracket=search_range
diff --git a/src/scgenerator/physics/simulate.py b/src/scgenerator/physics/simulate.py
index ea9872a..c7c9d87 100644
--- a/src/scgenerator/physics/simulate.py
+++ b/src/scgenerator/physics/simulate.py
@@ -395,22 +395,22 @@ class Simulations:
         self.logger.info(f"Finished simulations from config {self.name} !")
 
     def _run_available(self):
-        for varying, params in self.param_seq:
+        for variable, params in self.param_seq:
             io.save_parameters(
                 params,
-                io.generate_file_path("params.toml", self.id, utils.format_varying_list(varying)),
+                io.generate_file_path("params.toml", self.id, utils.format_variable_list(variable)),
             )
-            self.new_sim(varying, params)
+            self.new_sim(variable, params)
         self.finish()
 
-    def new_sim(self, varying_list: List[tuple], params: dict):
+    def new_sim(self, variable_list: List[tuple], params: dict):
         """responsible to launch a new simulation
 
         Parameters
         ----------
-        varying_list : list[tuple]
+        variable_list : list[tuple]
             list of tuples (name, value) where name is the name of a
-            varying parameter and value is its current value
+            variable parameter and value is its current value
         params : dict
             a flattened parameter dictionary, as returned by scgenerator.initialize.compute_init_parameters
         """
@@ -434,8 +434,8 @@ class Simulations:
 
 
 class SequencialSimulations(Simulations, available=True, priority=0):
-    def new_sim(self, varying_list: List[tuple], params: dict):
-        v_list_str = utils.format_varying_list(varying_list)
+    def new_sim(self, variable_list: List[tuple], params: dict):
+        v_list_str = utils.format_variable_list(variable_list)
         self.logger.info(f"launching simulation with {v_list_str}")
         self.propagator(
             params,
@@ -481,11 +481,11 @@ class RaySimulations(Simulations, available=using_ray, priority=1):
         self.jobs = []
         self.actors = {}
 
-    def new_sim(self, varying_list: List[tuple], params: dict):
+    def new_sim(self, variable_list: List[tuple], params: dict):
         while len(self.jobs) >= self.sim_jobs_total:
             self._collect_1_job()
 
-        v_list_str = utils.format_varying_list(varying_list)
+        v_list_str = utils.format_variable_list(variable_list)
 
         new_actor = self.propagator.remote(
             params, save_data=True, job_identifier=v_list_str, task_id=self.id
@@ -523,7 +523,7 @@ class RaySimulations(Simulations, available=using_ray, priority=1):
     @property
     def sim_jobs_total(self):
         tot_cpus = sum([node.get("Resources", {}).get("CPU", 0) for node in ray.nodes()])
-        return min(self.param_seq.num_sim, tot_cpus)
+        return int(min(self.param_seq.num_sim, tot_cpus))
 
 
 def new_simulations(
@@ -531,6 +531,7 @@ def new_simulations(
 ):
 
     config = io.load_toml(config_file)
+    io.set_environ(config)
     param_seq = initialize.ParamSequence(config)
 
     return _new_simulations(param_seq, task_id, data_folder, Method)
diff --git a/src/scgenerator/spectra.py b/src/scgenerator/spectra.py
new file mode 100644
index 0000000..7a3bf41
--- /dev/null
+++ b/src/scgenerator/spectra.py
@@ -0,0 +1,103 @@
+import os
+from collections.abc import Mapping, Sequence
+from glob import glob
+from typing import Any, List, Tuple
+
+import numpy as np
+
+from . import io
+from .logger import get_logger
+
+
+class Spectra(Sequence):
+    def __init__(self, path: str):
+        self.logger = get_logger(__name__)
+        self.path = path
+
+        if not os.path.isdir(self.path):
+            raise FileNotFoundError(f"Folder {self.path} does not exist")
+
+        self.params = None
+        try:
+            self.params = io.load_previous_parameters(os.path.join(self.path, "params.toml"))
+        except FileNotFoundError:
+            self.logger.info(f"parameters corresponding to {self.path} not found")
+
+        try:
+            self.z = np.load(os.path.join(path, "z.npy"))
+        except FileNotFoundError:
+            if self.params is not None:
+                self.z = self.params["z_targets"]
+            else:
+                raise
+
+        self.nmax = len(glob(os.path.join(self.path, "spectra_*.npy")))
+        if self.nmax <= 0:
+            raise FileNotFoundError(f"No appropriate file in specified folder {self.path}")
+
+    def __iter__(self):
+        """
+        similar to all_spectra but works as an iterator
+        """
+
+        self.logger.debug(f"iterating through {self.path}")
+        for i in range(self.nmax):
+            yield io.load_single_spectrum(self.path, i)
+
+    def __len__(self):
+        return self.nmax
+
+    def __getitem__(self, key):
+        return self.all_spectra(ind=range(self.nmax)[key])
+
+    def all_spectra(self, ind=None):
+        """
+        loads the data already simulated.
+        defauft shape is (z_targets, n, nt)
+
+        Parameters
+        ----------
+        ind : int or list of int
+        if only certain spectra are desired.
+                - If left to None, returns every spectrum
+                - If only 1 int, will cast the (1, n, nt) array into a (n, nt) array
+        Returns
+        ----------
+        spectra : array
+            squeezed array of complex spectra (n simulation on a nt size grid at each ind)
+        """
+
+        self.logger.debug(f"opening {self.path}")
+
+        # Check if file exists and assert how many z positions there are
+
+        if ind is None:
+            ind = range(self.nmax)
+        elif isinstance(ind, int):
+            ind = [ind]
+
+        # Load the spectra
+        spectra = []
+        for i in ind:
+            spectra.append(io.load_single_spectrum(self.path, i))
+        spectra = np.array(spectra)
+
+        self.logger.debug(f"all spectra from {self.path} successfully loaded")
+
+        return spectra.squeeze()
+
+
+class SpectraCollection(Mapping, Sequence):
+    def __init__(self, path: str):
+        self.path = path
+        self.collection: List[Spectra] = []
+        if not os.path.isdir(self.path):
+            raise FileNotFoundError(f"Folder {self.path} does not exist")
+
+        self.variable_list
+
+    def __getitem__(self, key):
+        return self.collection[key]
+
+    def __len__(self):
+        pass
diff --git a/src/scgenerator/utils.py b/src/scgenerator/utils.py
index 34fa414..edfb106 100644
--- a/src/scgenerator/utils.py
+++ b/src/scgenerator/utils.py
@@ -8,13 +8,14 @@ scgenerator module but some function may be used in any python program
 import datetime as dt
 import itertools
 import logging
+import socket
 from typing import Any, Callable, List, Tuple, Union
 
 import numpy as np
 import ray
 from copy import deepcopy
 
-from .const import PARAM_SEPARATOR, valid_varying
+from .const import PARAM_SEPARATOR, PREFIX_KEY_BASE, valid_variable
 from .logger import get_logger
 from .math import *
 
@@ -82,38 +83,22 @@ class ProgressTracker:
         return "{}/{}".format(self.current, self.max)
 
 
-# def ray_safe(func, *args, **kwargs):
-#     """evaluates functions that return None whether they are Ray workers or normal functions
-#     Parameters
-#     ----------
-#         func : the function or Worker id
-#         args : arguments to give to the functions
-#     Returns
-#     ----------
-#         nothing
-#     """
-#     if hasattr(func, "remote"):
-#         ray.get(func.remote(*args, **kwargs))
-#     else:
-#         func(*args, **kwargs)
-
-
 def count_variations(config: dict) -> Tuple[int, int]:
-    """returns (sim_num, varying_params_num) where sim_num is the total number of simulations required and
-    varying_params_num is the number of distinct parameters that will vary."""
+    """returns (sim_num, variable_params_num) where sim_num is the total number of simulations required and
+    variable_params_num is the number of distinct parameters that will vary."""
     sim_num = 1
-    varying_params_num = 0
+    variable_params_num = 0
 
-    for section_name in valid_varying:
-        for array in config.get(section_name, {}).get("varying", {}).values():
+    for section_name in valid_variable:
+        for array in config.get(section_name, {}).get("variable", {}).values():
             sim_num *= len(array)
-            varying_params_num += 1
+            variable_params_num += 1
 
     sim_num *= config["simulation"].get("repeat", 1)
-    return sim_num, varying_params_num
+    return sim_num, variable_params_num
 
 
-def format_varying_list(l: List[tuple]):
+def format_variable_list(l: List[tuple]):
     joints = 2 * PARAM_SEPARATOR
     str_list = []
     for p_name, p_value in l:
@@ -123,7 +108,18 @@ def format_varying_list(l: List[tuple]):
     return joints[0].join(str_list)
 
 
-# def varying_list_from_path(s: str) -> List[tuple]:
+def format_value(value):
+    if type(value) == type(False):
+        return str(value)
+    elif isinstance(value, (float, int)):
+        return format(value, ".9g")
+    elif isinstance(value, (list, tuple, np.ndarray)):
+        return "-".join([format_value(v) for v in value])
+    else:
+        return str(value)
+
+
+# def variable_list_from_path(s: str) -> List[tuple]:
 #     s = s.replace("/", "")
 #     str_list = s.split(PARAM_SEPARATOR)
 #     out = []
@@ -132,69 +128,59 @@ def format_varying_list(l: List[tuple]):
 #     return out
 
 
-def format_value(value):
-    if type(value) == type(False):
-        return str(value)
-    elif isinstance(value, (float, int)):
-        return format(value, ".5g")
-    elif isinstance(value, (list, tuple, np.ndarray)):
-        return "-".join([format_value(v) for v in value])
-    else:
-        return str(value)
+# def get_value(s: str):
+#     if s.lower() == "true":
+#         return True
+#     if s.lower() == "false":
+#         return False
+
+#     try:
+#         return int(s)
+#     except ValueError:
+#         pass
+
+#     try:
+#         return float(s)
+#     except ValueError:
+#         pass
+
+#     return s
 
 
-def get_value(s: str):
-    if s.lower() == "true":
-        return True
-    if s.lower() == "false":
-        return False
-
-    try:
-        return int(s)
-    except ValueError:
-        pass
-
-    try:
-        return float(s)
-    except ValueError:
-        pass
-
-    return s
-
-
-def varying_iterator(config):
+def variable_iterator(config):
     out = deepcopy(config)
-    varying_dict = {
-        section_name: out.get(section_name, {}).pop("varying", {}) for section_name in valid_varying
+    variable_dict = {
+        section_name: out.get(section_name, {}).pop("variable", {})
+        for section_name in valid_variable
     }
 
     possible_keys = []
     possible_ranges = []
 
-    for section_name, section in varying_dict.items():
+    for section_name, section in variable_dict.items():
         for key in section:
-            arr = varying_dict[section_name][key]
+            arr = variable_dict[section_name][key]
             possible_keys.append((section_name, key))
             possible_ranges.append(range(len(arr)))
 
     combinations = itertools.product(*possible_ranges)
 
     for combination in combinations:
-        only_varying = []
+        only_variable = []
         for i, key in enumerate(possible_keys):
-            parameter_value = varying_dict[key[0]][key[1]][combination[i]]
+            parameter_value = variable_dict[key[0]][key[1]][combination[i]]
             out[key[0]][key[1]] = parameter_value
-            only_varying.append((key[1], parameter_value))
-        yield only_varying, out
+            only_variable.append((key[1], parameter_value))
+        yield only_variable, out
 
 
 def parallelize(func, arg_iter, sim_jobs=4, progress_tracker_kwargs=None, const_kwarg={}):
-    """given a function and an iterator of arguments, runs the function in parallel
+    """given a function and an iterable of arguments, runs the function in parallel
     Parameters
     ----------
         func : a function
-        arg_iter : an iterator that yields a tuple to be unpacked to the function as argument(s)
-        sim_jobs : number of simultaneous runs
+        arg_iter : an iterable that yields a tuple to be unpacked to the function as argument(s)
+        sim_jobs : number of parallel runs
         progress_tracker_kwargs : key word arguments to be passed to the ProgressTracker
         const_kwarg : keyword arguments to be passed to the function on every run
 
@@ -235,3 +221,8 @@ def parallelize(func, arg_iter, sim_jobs=4, progress_tracker_kwargs=None, const_
             ray.get(pt.update.remote())
 
     return np.array(results)
+
+
+def formatted_hostname():
+    s = socket.gethostname().replace(".", "_")
+    return (PREFIX_KEY_BASE + s).upper()
\ No newline at end of file
diff --git a/testing/configs/count_variations/120sim_3vary.toml b/testing/configs/count_variations/120sim_3vary.toml
new file mode 100644
index 0000000..8824349
--- /dev/null
+++ b/testing/configs/count_variations/120sim_3vary.toml
@@ -0,0 +1,25 @@
+[fiber]
+core_radius = 50e-6
+length = 50e-2
+model = "marcatili"
+
+[gas.variable]
+gas_name = ["air", "helium"]
+
+[pulse]
+power = 100e3
+wavelength = 800e-9
+
+[pulse.variable]
+width = [250e-15, 240e-15, 230e-15, 220e-15, 210e-15]
+
+[simulation]
+parallel = true
+repeat = 4
+t_num = 16384
+time_window = 37e-12
+tolerated_error = 1e-11
+z_num = 128
+
+[simulation.variable]
+behaviors = [["spm", "raman", "ss"], ["spm", "raman"], ["spm"]]
diff --git a/testing/configs/count_variations/1sim_1vary.toml b/testing/configs/count_variations/1sim_1vary.toml
index 1d80f6e..c9053f8 100644
--- a/testing/configs/count_variations/1sim_1vary.toml
+++ b/testing/configs/count_variations/1sim_1vary.toml
@@ -10,7 +10,7 @@ gas_name = "air"
 power = 100e3
 wavelength = 800e-9
 
-[pulse.varying]
+[pulse.variable]
 width = [250e-15]
 
 [simulation]
diff --git a/testing/configs/count_variations/2sim_1vary.toml b/testing/configs/count_variations/2sim_1vary.toml
index ed5b9ca..71dd68c 100644
--- a/testing/configs/count_variations/2sim_1vary.toml
+++ b/testing/configs/count_variations/2sim_1vary.toml
@@ -11,7 +11,7 @@ soliton_num = 5
 wavelength = 800e-9
 width = 250e-15
 
-[pulse.varying]
+[pulse.variable]
 shape = ["gaussian", "sech"]
 
 [simulation]
diff --git a/testing/configs/ensure_consistency/bad1.toml b/testing/configs/ensure_consistency/bad1.toml
index 9aee427..6a6b025 100644
--- a/testing/configs/ensure_consistency/bad1.toml
+++ b/testing/configs/ensure_consistency/bad1.toml
@@ -15,7 +15,7 @@ quantum_noise = true
 shape = "gaussian"
 wavelength = 1050e-9
 
-[pulse.varying]
+[pulse.variable]
 intensity_noise = [0.05e-2, 0.1e-2]
 
 [simulation]
diff --git a/testing/configs/ensure_consistency/bad2.toml b/testing/configs/ensure_consistency/bad2.toml
index 25c7b43..b7be419 100644
--- a/testing/configs/ensure_consistency/bad2.toml
+++ b/testing/configs/ensure_consistency/bad2.toml
@@ -14,7 +14,7 @@ quantum_noise = true
 shape = "gaussian"
 wavelength = 1050e-9
 
-[pulse.varying]
+[pulse.variable]
 intensity_noise = [0.05e-2, 0.1e-2]
 soliton_num = [1, 2, 3, 4]
 
diff --git a/testing/configs/ensure_consistency/bad3.toml b/testing/configs/ensure_consistency/bad3.toml
index 82c6f77..b96982c 100644
--- a/testing/configs/ensure_consistency/bad3.toml
+++ b/testing/configs/ensure_consistency/bad3.toml
@@ -15,7 +15,7 @@ quantum_noise = true
 shape = "gaussian"
 wavelength = 1050e-9
 
-[pulse.varying]
+[pulse.variable]
 intensity_noise = [0.05e-2, 0.1e-2]
 width = [50e-15, 100e-15, 200e-15]
 
diff --git a/testing/configs/ensure_consistency/bad4.toml b/testing/configs/ensure_consistency/bad4.toml
index 026c8b2..a5fa972 100644
--- a/testing/configs/ensure_consistency/bad4.toml
+++ b/testing/configs/ensure_consistency/bad4.toml
@@ -16,7 +16,7 @@ shape = "gaussian"
 wavelength = 1050e-9
 width = 120e-15
 
-[pulse.varying]
+[pulse.variable]
 intensity_noise = [0.05e-2, 0.1e-2]
 width = [50e-15, 100e-15, 200e-15]
 
diff --git a/testing/configs/ensure_consistency/bad5.toml b/testing/configs/ensure_consistency/bad5.toml
index 991abe0..c7aa6f3 100644
--- a/testing/configs/ensure_consistency/bad5.toml
+++ b/testing/configs/ensure_consistency/bad5.toml
@@ -17,7 +17,7 @@ quantum_noise = true
 shape = "gaussian"
 wavelength = 1050e-9
 
-[pulse.varying]
+[pulse.variable]
 intensity_noise = [0.05e-2, 0.1e-2]
 width = [50e-15, 100e-15, 200e-15]
 
diff --git a/testing/configs/ensure_consistency/bad6.toml b/testing/configs/ensure_consistency/bad6.toml
index be5bf23..b7f2690 100644
--- a/testing/configs/ensure_consistency/bad6.toml
+++ b/testing/configs/ensure_consistency/bad6.toml
@@ -16,7 +16,7 @@ quantum_noise = true
 shape = "gaussian"
 wavelength = 1050e-9
 
-[pulse.varying]
+[pulse.variable]
 intensity_noise = [0.05e-2, 0.1e-2]
 width = [50e-15, 100e-15, 200e-15]
 
diff --git a/testing/configs/ensure_consistency/good1.toml b/testing/configs/ensure_consistency/good1.toml
index de6a009..6deb910 100644
--- a/testing/configs/ensure_consistency/good1.toml
+++ b/testing/configs/ensure_consistency/good1.toml
@@ -14,7 +14,7 @@ quantum_noise = true
 shape = "gaussian"
 wavelength = 1050e-9
 
-[pulse.varying]
+[pulse.variable]
 intensity_noise = [0.05e-2, 0.1e-2]
 width = [50e-15, 100e-15, 200e-15]
 
diff --git a/testing/configs/ensure_consistency/good2.toml b/testing/configs/ensure_consistency/good2.toml
index c9f93d6..3f3ad07 100644
--- a/testing/configs/ensure_consistency/good2.toml
+++ b/testing/configs/ensure_consistency/good2.toml
@@ -15,7 +15,7 @@ quantum_noise = true
 shape = "gaussian"
 wavelength = 1050e-9
 
-[pulse.varying]
+[pulse.variable]
 intensity_noise = [0.05e-2, 0.1e-2]
 width = [50e-15, 100e-15, 200e-15]
 
diff --git a/testing/configs/ensure_consistency/good3.toml b/testing/configs/ensure_consistency/good3.toml
index 7e8a56e..8a7d0a1 100644
--- a/testing/configs/ensure_consistency/good3.toml
+++ b/testing/configs/ensure_consistency/good3.toml
@@ -13,7 +13,7 @@ quantum_noise = true
 shape = "gaussian"
 wavelength = 1050e-9
 
-[pulse.varying]
+[pulse.variable]
 intensity_noise = [0.05e-2, 0.1e-2]
 width = [50e-15, 100e-15, 200e-15]
 
diff --git a/testing/configs/ensure_consistency/good4.toml b/testing/configs/ensure_consistency/good4.toml
index b357f2c..bd857e0 100644
--- a/testing/configs/ensure_consistency/good4.toml
+++ b/testing/configs/ensure_consistency/good4.toml
@@ -14,7 +14,7 @@ model = "hasan"
 [gas]
 gas_name = "helium"
 
-[gas.varying]
+[gas.variable]
 temperature = [300, 350, 400]
 
 [pulse]
@@ -23,7 +23,7 @@ quantum_noise = true
 shape = "gaussian"
 wavelength = 1050e-9
 
-[pulse.varying]
+[pulse.variable]
 intensity_noise = [0.05e-2, 0.1e-2]
 width = [50e-15, 100e-15, 200e-15]
 
diff --git a/testing/configs/ensure_consistency/good5.toml b/testing/configs/ensure_consistency/good5.toml
index 48588b3..c0e724d 100644
--- a/testing/configs/ensure_consistency/good5.toml
+++ b/testing/configs/ensure_consistency/good5.toml
@@ -14,7 +14,7 @@ quantum_noise = true
 shape = "gaussian"
 wavelength = 1050e-9
 
-[pulse.varying]
+[pulse.variable]
 intensity_noise = [0.05e-2, 0.1e-2]
 width = [50e-15, 100e-15, 200e-15]
 
diff --git a/testing/configs/ensure_consistency/good6.toml b/testing/configs/ensure_consistency/good6.toml
index 0778cf1..1a591bd 100644
--- a/testing/configs/ensure_consistency/good6.toml
+++ b/testing/configs/ensure_consistency/good6.toml
@@ -16,7 +16,7 @@ quantum_noise = true
 shape = "gaussian"
 wavelength = 1050e-9
 
-[pulse.varying]
+[pulse.variable]
 intensity_noise = [0.05e-2, 0.1e-2]
 width = [50e-15, 100e-15, 200e-15]
 
diff --git a/testing/configs/param_sequence/almost_equal.toml b/testing/configs/param_sequence/almost_equal.toml
new file mode 100644
index 0000000..28f4ae2
--- /dev/null
+++ b/testing/configs/param_sequence/almost_equal.toml
@@ -0,0 +1,29 @@
+# raman_type should be added
+
+name = "test config"
+
+[fiber]
+gamma = 0.018
+length = 1
+model = "pcf"
+pitch = 1.5e-6
+pitch_ratio = 0.37
+
+[pulse]
+power = 100e3
+quantum_noise = true
+shape = "gaussian"
+wavelength = 1050e-9
+width = 50e-15
+
+[pulse.variable]
+intensity_noise = [0.10000000005e-2, 0.1e-2]
+
+[simulation]
+behaviors = ["spm", "raman", "ss"]
+parallel = true
+repeat = 4
+t_num = 16384
+time_window = 37e-12
+tolerated_error = 1e-11
+z_num = 128
diff --git a/testing/configs/param_sequence/equal.toml b/testing/configs/param_sequence/equal.toml
new file mode 100644
index 0000000..9e09297
--- /dev/null
+++ b/testing/configs/param_sequence/equal.toml
@@ -0,0 +1,29 @@
+# raman_type should be added
+
+name = "test config"
+
+[fiber]
+gamma = 0.018
+length = 1
+model = "pcf"
+pitch = 1.5e-6
+pitch_ratio = 0.37
+
+[pulse]
+power = 100e3
+quantum_noise = true
+shape = "gaussian"
+wavelength = 1050e-9
+width = 50e-15
+
+[pulse.variable]
+intensity_noise = [0.1e-2, 0.001]
+
+[simulation]
+behaviors = ["spm", "raman", "ss"]
+parallel = true
+repeat = 4
+t_num = 16384
+time_window = 37e-12
+tolerated_error = 1e-11
+z_num = 128
diff --git a/testing/configs/param_sequence/no_variations.toml b/testing/configs/param_sequence/no_variations.toml
new file mode 100644
index 0000000..3a88879
--- /dev/null
+++ b/testing/configs/param_sequence/no_variations.toml
@@ -0,0 +1,27 @@
+# raman_type should be added
+
+name = "test config"
+
+[fiber]
+gamma = 0.018
+length = 1
+model = "pcf"
+pitch = 1.5e-6
+pitch_ratio = 0.37
+
+[pulse]
+intensity_noise = 0.1e-2
+power = 100e3
+quantum_noise = true
+shape = "gaussian"
+wavelength = 1050e-9
+width = 50e-15
+
+[simulation]
+behaviors = ["spm", "raman", "ss"]
+parallel = true
+repeat = 4
+t_num = 16384
+time_window = 37e-12
+tolerated_error = 1e-11
+z_num = 128
diff --git a/testing/configs/run_simulations/full_anomalous.toml b/testing/configs/run_simulations/full_anomalous.toml
index af4b1bb..4aac3b1 100644
--- a/testing/configs/run_simulations/full_anomalous.toml
+++ b/testing/configs/run_simulations/full_anomalous.toml
@@ -19,7 +19,7 @@ length = 0.02
 power = 10000
 t0 = 2.84e-14
 
-[pulse.varying]
+[pulse.variable]
 wavelength = [835e-9, 830e-9]
 
 [simulation]
diff --git a/testing/configs/validate_types/bad1.toml b/testing/configs/validate_types/bad1.toml
index 6f8c7ca..47fd4cf 100644
--- a/testing/configs/validate_types/bad1.toml
+++ b/testing/configs/validate_types/bad1.toml
@@ -15,7 +15,7 @@ quantum_noise = true
 shape = "gaussian"
 wavelength = 1050e-9
 
-[pulse.varying]
+[pulse.variable]
 intensity_noise = [0.05e-2, 0.1e-2]
 width = [50e-15, 100e-15, 200e-15]
 
diff --git a/testing/configs/validate_types/bad2.toml b/testing/configs/validate_types/bad2.toml
index 30ff28b..120451c 100644
--- a/testing/configs/validate_types/bad2.toml
+++ b/testing/configs/validate_types/bad2.toml
@@ -15,7 +15,7 @@ quantum_noise = true
 shape = "gaussian"
 wavelength = 1050e-9
 
-[pulse.varying]
+[pulse.variable]
 intensity_noise = [0.05e-2, 0.1e-2]
 width = [50e-15, 100e-15, 200e-15]
 
diff --git a/testing/configs/validate_types/bad3.toml b/testing/configs/validate_types/bad3.toml
index 1e1a291..68bc9f8 100644
--- a/testing/configs/validate_types/bad3.toml
+++ b/testing/configs/validate_types/bad3.toml
@@ -15,7 +15,7 @@ quantum_noise = true
 shape = "gaussian"
 wavelength = 1050e-9
 
-[pulse.varying]
+[pulse.variable]
 intensity_noise = [0.05e-2, 0.1e-2]
 width = ["gaussian", "sech"]
 
diff --git a/testing/configs/validate_types/bad4.toml b/testing/configs/validate_types/bad4.toml
index 81dcc69..20cf1fc 100644
--- a/testing/configs/validate_types/bad4.toml
+++ b/testing/configs/validate_types/bad4.toml
@@ -1,4 +1,4 @@
-# parallel should not be varying
+# parallel should not be variable
 
 name = "test config"
 
@@ -15,7 +15,7 @@ quantum_noise = true
 shape = "gaussian"
 wavelength = 1050e-9
 
-[pulse.varying]
+[pulse.variable]
 intensity_noise = [0.05e-2, 0.1e-2]
 width = [50e-15, 100e-15, 200e-15]
 
@@ -28,5 +28,5 @@ time_window = 37e-12
 tolerated_error = 1e-11
 z_num = 1
 
-[simulation.varying]
+[simulation.variable]
 parallel = [true, false]
diff --git a/testing/configs/validate_types/bad5.toml b/testing/configs/validate_types/bad5.toml
index 114515f..b1448da 100644
--- a/testing/configs/validate_types/bad5.toml
+++ b/testing/configs/validate_types/bad5.toml
@@ -1,4 +1,4 @@
-#varying parameters should be lists
+#variable parameters should be lists
 
 name = "test config"
 
@@ -15,7 +15,7 @@ quantum_noise = true
 shape = "gaussian"
 wavelength = 1050e-9
 
-[pulse.varying]
+[pulse.variable]
 intensity_noise = 0.05e-2
 width = [50e-15, 100e-15, 200e-15]
 
diff --git a/testing/configs/validate_types/bad6.toml b/testing/configs/validate_types/bad6.toml
index 6904f23..9cc9ced 100644
--- a/testing/configs/validate_types/bad6.toml
+++ b/testing/configs/validate_types/bad6.toml
@@ -16,7 +16,7 @@ quantum_noise = true
 shape = "gaussian"
 wavelength = 1050e-9
 
-[pulse.varying]
+[pulse.variable]
 width = [50e-15, 100e-15, 200e-15]
 
 [simulation]
diff --git a/testing/configs/validate_types/bad7.toml b/testing/configs/validate_types/bad7.toml
index ccf5466..0b87595 100644
--- a/testing/configs/validate_types/bad7.toml
+++ b/testing/configs/validate_types/bad7.toml
@@ -13,7 +13,7 @@ quantum_noise = true
 shape = "gaussian"
 wavelength = 1050e-9
 
-[pulse.varying]
+[pulse.variable]
 intensity_noise = []
 width = [50e-15, 100e-15, 200e-15]
 
diff --git a/testing/configs/validate_types/good.toml b/testing/configs/validate_types/good.toml
index f8ec86c..7c3876e 100644
--- a/testing/configs/validate_types/good.toml
+++ b/testing/configs/validate_types/good.toml
@@ -13,7 +13,7 @@ quantum_noise = true
 shape = "gaussian"
 wavelength = 1050e-9
 
-[pulse.varying]
+[pulse.variable]
 intensity_noise = [0.05e-2, 0.1e-2]
 width = [50e-15, 100e-15, 200e-15]
 
diff --git a/testing/long_tests/test_recovery_param_seq.py b/testing/long_tests/test_recovery_param_seq.py
new file mode 100644
index 0000000..cc1896e
--- /dev/null
+++ b/testing/long_tests/test_recovery_param_seq.py
@@ -0,0 +1,36 @@
+import shutil
+import unittest
+
+import toml
+from scgenerator import initialize, io, logger
+from send2trash import send2trash
+
+TMP = "testing/.tmp"
+
+
+class TestRecoveryParamSequence(unittest.TestCase):
+    def setUp(self):
+        shutil.copytree("/Users/benoitsierro/sc_tests/scgenerator_full anomalous55", TMP)
+        self.conf = toml.load(TMP + "/initial_config.toml")
+        logger.DEFAULT_LEVEL = logger.logging.FATAL
+        io.set_data_folder(55, TMP)
+
+    def test_remaining_simulations_count(self):
+        param_seq = initialize.RecoveryParamSequence(self.conf, 55)
+        self.assertEqual(5, len(param_seq))
+
+    def test_only_one_to_complete(self):
+        param_seq = initialize.RecoveryParamSequence(self.conf, 55)
+        i = 0
+        for expected, (vary_list, params) in zip([True, False, False, False, False], param_seq):
+            i += 1
+            self.assertEqual(expected, "recovery_last_stored" in params)
+
+        self.assertEqual(5, i)
+
+    def tearDown(self):
+        send2trash(TMP)
+
+
+if __name__ == "__main__":
+    unittest.main()
diff --git a/testing/test_initialize.py b/testing/test_initialize.py
index a090232..1ba270d 100644
--- a/testing/test_initialize.py
+++ b/testing/test_initialize.py
@@ -1,8 +1,10 @@
 import unittest
-import toml
+from copy import deepcopy
+
 import scgenerator.initialize as init
+import toml
+from scgenerator import utils
 from scgenerator.errors import *
-from prettyprinter import pprint
 
 
 def load_conf(name):
@@ -18,6 +20,36 @@ def conf_maker(folder):
     return conf
 
 
+class TestParamSequence(unittest.TestCase):
+    def iterconf(self, files):
+        conf = conf_maker("param_sequence")
+        for path in files:
+            yield init.ParamSequence(conf(path))
+
+    def test_no_repeat_in_sub_folder_names(self):
+        for param_seq in self.iterconf(["almost_equal", "equal", "no_variations"]):
+            l = []
+            s = []
+            for vary_list, _ in param_seq.iterate_without_computing():
+                self.assertNotIn(vary_list, l)
+                self.assertNotIn(utils.format_variable_list(vary_list), s)
+                l.append(vary_list)
+                s.append(utils.format_variable_list(vary_list))
+
+    def test_init_config_not_affected_by_iteration(self):
+        for param_seq in self.iterconf(["almost_equal", "equal", "no_variations"]):
+            config = deepcopy(param_seq.config)
+            for _ in param_seq.iterate_without_computing():
+                self.assertEqual(config.items(), param_seq.config.items())
+
+    def test_no_variations_yields_only_num_and_id(self):
+        for param_seq in self.iterconf(["no_variations"]):
+            for vary_list, _ in param_seq.iterate_without_computing():
+                self.assertEqual(vary_list[1][0], "num")
+                self.assertEqual(vary_list[0][0], "id")
+                self.assertEqual(2, len(vary_list))
+
+
 class TestInitializeMethods(unittest.TestCase):
     def test_validate_types(self):
         conf = lambda s: load_conf("validate_types/" + s)
diff --git a/testing/test_utils.py b/testing/test_utils.py
index 036bb46..74388bb 100644
--- a/testing/test_utils.py
+++ b/testing/test_utils.py
@@ -1,6 +1,8 @@
 import unittest
-from scgenerator import utils, initialize
+
+import numpy as np
 import toml
+from scgenerator import initialize, utils
 
 
 def load_conf(name):
@@ -20,11 +22,34 @@ class TestUtilsMethods(unittest.TestCase):
     def test_count_variations(self):
         conf = conf_maker("count_variations")
 
-        self.assertEqual((1, 0), utils.count_variations(conf("1sim_0vary")))
-        self.assertEqual((1, 1), utils.count_variations(conf("1sim_1vary")))
-        self.assertEqual((2, 1), utils.count_variations(conf("2sim_1vary")))
-        self.assertEqual((2, 0), utils.count_variations(conf("2sim_0vary")))
+        for sim, vary in [(1, 0), (1, 1), (2, 1), (2, 0), (120, 3)]:
+            self.assertEqual((sim, vary), utils.count_variations(conf(f"{sim}sim_{vary}vary")))
+
+    def test_format_value(self):
+        values = [
+            122e-6,
+            True,
+            ["raman", "ss"],
+            np.arange(5),
+            1.123,
+            1.1230001,
+            0.002e122,
+            12.3456e-9,
+        ]
+        s = [
+            "0.000122",
+            "True",
+            "raman-ss",
+            "0-1-2-3-4",
+            "1.123",
+            "1.1230001",
+            "2e+119",
+            "1.23456e-08",
+        ]
+
+        for value, target in zip(values, s):
+            self.assertEqual(target, utils.format_value(value))
 
 
 if __name__ == "__main__":
-    unittest.main()
\ No newline at end of file
+    unittest.main()