diff --git a/src/scgenerator/initialize.py b/src/scgenerator/initialize.py
index 7741bcb..1c91c2d 100644
--- a/src/scgenerator/initialize.py
+++ b/src/scgenerator/initialize.py
@@ -675,23 +675,35 @@ def compute_init_parameters(config: Dict[str, Any]) -> Dict[str, Any]:
 
 
 def setup_custom_field(params: Dict[str, Any]) -> bool:
+    """sets up a custom field function if necessary and returns
+    True if it did so, False otherwise
+
+    Parameters
+    ----------
+    params : Dict[str, Any]
+        params dictionary
+
+    Returns
+    -------
+    bool
+        True if the field has been modified
+    """
     logger = get_logger(__name__)
-    custom_field = True
     if "prev_data_dir" in params:
         spec = io.load_last_spectrum(Path(params["prev_data_dir"]))[1]
-        params["field_0"] = np.fft.ifft(spec) * params["input_transmission"]
-    elif "field_file" in params:
-        field_data = np.load(params["field_file"])
-        field_interp = interp1d(
-            field_data["time"], field_data["field"], bounds_error=False, fill_value=(0, 0)
-        )
-        params["field_0"] = field_interp(params["t"])
-    elif "field_0" in params:
-        params = _evalutate_custom_field_equation(params)
+        params["field_0"] = np.fft.ifft(spec) * np.sqrt(params["input_transmission"])
     else:
-        custom_field = False
+        if "field_file" in params:
+            field_data = np.load(params["field_file"])
+            field_interp = interp1d(
+                field_data["time"], field_data["field"], bounds_error=False, fill_value=(0, 0)
+            )
+            params["field_0"] = field_interp(params["t"])
+        elif "field_0" in params:
+            params = _evalutate_custom_field_equation(params)
+        else:
+            return False
 
-    if custom_field:
         params["field_0"] = params["field_0"] * pulse.modify_field_ratio(
             params["t"],
             params["field_0"],
@@ -706,7 +718,7 @@ def setup_custom_field(params: Dict[str, Any]) -> bool:
         logger.debug(f"had to adjust w by {delta_w}")
         params["wavelength"] = units.m.inv(units.m(params["wavelength"]) - delta_w)
         _update_frequency_domain(params)
-    return custom_field
+    return True
 
 
 def _update_pulse_parameters(params):
diff --git a/src/scgenerator/physics/pulse.py b/src/scgenerator/physics/pulse.py
index 0662f35..00cb831 100644
--- a/src/scgenerator/physics/pulse.py
+++ b/src/scgenerator/physics/pulse.py
@@ -11,7 +11,7 @@ n is the number of spectra at the same z position and nt is the size of the time
 
 import itertools
 import os
-from typing import Tuple
+from typing import Literal, Tuple
 
 import matplotlib.pyplot as plt
 import numpy as np
@@ -115,14 +115,14 @@ def modify_field_ratio(
 
 
 def conform_pulse_params(
-    shape,
-    width=None,
-    t0=None,
-    peak_power=None,
-    energy=None,
-    soliton_num=None,
-    gamma=None,
-    beta2=None,
+    shape: Literal["gaussian", "sech"],
+    width: float = None,
+    t0: float = None,
+    peak_power: float = None,
+    energy: float = None,
+    soliton_num: float = None,
+    gamma: float = None,
+    beta2: float = None,
 ):
     """makes sure all parameters of the pulse are set and consistent
 
diff --git a/src/scgenerator/scripts/slurm_submit.py b/src/scgenerator/scripts/slurm_submit.py
index 3dbcbb5..1d46265 100644
--- a/src/scgenerator/scripts/slurm_submit.py
+++ b/src/scgenerator/scripts/slurm_submit.py
@@ -4,12 +4,65 @@ import re
 import shutil
 import subprocess
 from datetime import datetime, timedelta
+from typing import Tuple
+import numpy as np
 
 from ..initialize import validate_config_sequence
 from ..io import Paths
 from ..utils import count_variations
 
 
+def primes(n):
+    primfac = []
+    d = 2
+    while d * d <= n:
+        while (n % d) == 0:
+            primfac.append(d)  # supposing you want multiple factors repeated
+            n //= d
+        d += 1
+    if n > 1:
+        primfac.append(n)
+    return primfac
+
+
+def balance(n, lim=(32, 32)):
+    factors = primes(n)
+    if len(factors) == 1:
+        factors = primes(n + 1)
+    a, b, x, y = 1, 1, 1, 1
+    while len(factors) > 0 and x <= lim[0] and y <= lim[1]:
+        a = x
+        b = y
+        if y >= x:
+            x *= factors.pop(0)
+        else:
+            y *= factors.pop()
+    return a, b
+
+
+def distribute(
+    num: int, nodes: int = None, cpus_per_node: int = None, lim=(16, 32)
+) -> Tuple[int, int]:
+    if nodes is None and cpus_per_node is None:
+        balanced = balance(num, lim)
+        if num > max(lim):
+            while np.product(balanced) < min(lim):
+                num += 1
+                balanced = balance(num, lim)
+        nodes = min(balanced)
+        cpus_per_node = max(balanced)
+
+    elif nodes is None:
+        nodes = num // cpus_per_node
+        while nodes > lim[0]:
+            nodes //= 2
+    elif cpus_per_node is None:
+        cpus_per_node = num // nodes
+        while cpus_per_node > lim[1]:
+            cpus_per_node //= 2
+    return nodes, cpus_per_node
+
+
 def format_time(t):
     try:
         t = float(t)
@@ -25,9 +78,9 @@ def create_parser():
         "-t", "--time", required=True, type=str, help="time required for the job in hh:mm:ss"
     )
     parser.add_argument(
-        "-c", "--cpus-per-node", required=True, type=int, help="number of cpus required per node"
+        "-c", "--cpus-per-node", default=None, type=int, help="number of cpus required per node"
     )
-    parser.add_argument("-n", "--nodes", required=True, type=int, help="number of nodes required")
+    parser.add_argument("-n", "--nodes", default=None, type=int, help="number of nodes required")
     parser.add_argument(
         "--environment-setup",
         required=False,
@@ -70,6 +123,8 @@ def main():
 
     sim_num, _ = count_variations(final_config)
 
+    args.nodes, args.cpus_per_nodes = distribute(sim_num, args.nodes, args.cpus_per_nodes)
+
     file_name = (
         "submit " + final_config["name"] + "-" + format(datetime.now(), "%Y%m%d%H%M") + ".sh"
     )
diff --git a/src/scgenerator/utils.py b/src/scgenerator/utils.py
index cc66c54..1f31c35 100644
--- a/src/scgenerator/utils.py
+++ b/src/scgenerator/utils.py
@@ -25,10 +25,6 @@ from .const import PARAM_SEPARATOR, PREFIX_KEY_BASE, valid_variable, HUSH_PROGRE
 from .logger import get_logger
 from .math import *
 
-# XXX ############################################
-# XXX ############### Pure Python ################
-# XXX ############################################
-
 
 class PBars:
     @classmethod
@@ -245,34 +241,6 @@ def format_value(value):
         return str(value)
 
 
-# def variable_list_from_path(s: str) -> List[tuple]:
-#     s = s.replace("/", "")
-#     str_list = s.split(PARAM_SEPARATOR)
-#     out = []
-#     for i in range(0, len(str_list) // 2 * 2, 2):
-#         out.append((str_list[i], get_value(str_list[i + 1])))
-#     return out
-
-
-# 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 variable_iterator(config) -> Iterator[Tuple[List[Tuple[str, Any]], dict]]:
     """given a config with "variable" parameters, iterates through every possible combination,
     yielding a a list of (parameter_name, value) tuples and a full config dictionary.
@@ -385,7 +353,7 @@ def parallelize(func, arg_iter, sim_jobs=4, progress_tracker_kwargs=None, const_
     return np.array(results)
 
 
-def deep_update(d: Mapping, u: Mapping):
+def deep_update(d: Mapping, u: Mapping) -> dict:
     for k, v in u.items():
         if isinstance(v, collections.abc.Mapping):
             d[k] = deep_update(d.get(k, {}), v)
diff --git a/testing/configs/custom_field/init_field.npz b/testing/configs/custom_field/init_field.npz
new file mode 100644
index 0000000..e5687ed
Binary files /dev/null and b/testing/configs/custom_field/init_field.npz differ
diff --git a/testing/configs/custom_field/mean_power.toml b/testing/configs/custom_field/mean_power.toml
new file mode 100644
index 0000000..953ec5c
--- /dev/null
+++ b/testing/configs/custom_field/mean_power.toml
@@ -0,0 +1,8 @@
+dt = 1e-15
+field_file = "testing/configs/custom_field/init_field.npz"
+length = 1
+mean_power = 220e-3
+repetition_rate = 40e6
+t_num = 2048
+wavelength = 1000e-9
+z_num = 32
diff --git a/testing/configs/custom_field/no_change.toml b/testing/configs/custom_field/no_change.toml
new file mode 100644
index 0000000..288b1fb
--- /dev/null
+++ b/testing/configs/custom_field/no_change.toml
@@ -0,0 +1,6 @@
+dt = 1e-15
+field_file = "testing/configs/custom_field/init_field.npz"
+length = 1
+t_num = 2048
+wavelength = 1000e-9
+z_num = 32
diff --git a/testing/configs/custom_field/peak_power.toml b/testing/configs/custom_field/peak_power.toml
new file mode 100644
index 0000000..e658d0a
--- /dev/null
+++ b/testing/configs/custom_field/peak_power.toml
@@ -0,0 +1,7 @@
+dt = 1e-15
+field_file = "testing/configs/custom_field/init_field.npz"
+length = 1
+peak_power = 20000
+t_num = 2048
+wavelength = 1000e-9
+z_num = 32
diff --git a/testing/configs/custom_field/recover1.toml b/testing/configs/custom_field/recover1.toml
new file mode 100644
index 0000000..52400f3
--- /dev/null
+++ b/testing/configs/custom_field/recover1.toml
@@ -0,0 +1,7 @@
+dt = 1e-15
+input_transmission = 1
+length = 1
+prev_data_dir = "testing/configs/custom_field/recover_data"
+t_num = 2048
+wavelength = 1000e-9
+z_num = 32
diff --git a/testing/configs/custom_field/recover2.toml b/testing/configs/custom_field/recover2.toml
new file mode 100644
index 0000000..853b8ea
--- /dev/null
+++ b/testing/configs/custom_field/recover2.toml
@@ -0,0 +1,7 @@
+dt = 1e-15
+input_transmission = 0.9
+length = 1
+prev_data_dir = "testing/configs/custom_field/recover_data"
+t_num = 2048
+wavelength = 1000e-9
+z_num = 32
diff --git a/testing/configs/ensure_consistency/good1.toml b/testing/configs/ensure_consistency/good1.toml
index 194f6b0..c1b778d 100644
--- a/testing/configs/ensure_consistency/good1.toml
+++ b/testing/configs/ensure_consistency/good1.toml
@@ -5,6 +5,7 @@ name = "test config"
 [fiber]
 gamma = 0.018
 length = 1
+model = "pcf"
 pitch = 1.5e-6
 pitch_ratio = 0.37
 
diff --git a/testing/test_initialize.py b/testing/test_initialize.py
index 05d5cd2..f438a61 100644
--- a/testing/test_initialize.py
+++ b/testing/test_initialize.py
@@ -2,8 +2,9 @@ import unittest
 from copy import deepcopy
 
 import scgenerator.initialize as init
+import numpy as np
 import toml
-from scgenerator import utils
+from scgenerator import defaults, utils, math
 from scgenerator.errors import *
 
 
@@ -30,7 +31,7 @@ class TestParamSequence(unittest.TestCase):
         for param_seq in self.iterconf(["almost_equal", "equal", "no_variations"]):
             l = []
             s = []
-            for vary_list, _ in param_seq.iterate_without_computing():
+            for vary_list, _ in utils.required_simulations(param_seq.config):
                 self.assertNotIn(vary_list, l)
                 self.assertNotIn(utils.format_variable_list(vary_list), s)
                 l.append(vary_list)
@@ -39,12 +40,12 @@ class TestParamSequence(unittest.TestCase):
     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():
+            for _ in utils.required_simulations(param_seq.config):
                 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():
+            for vary_list, _ in utils.required_simulations(param_seq.config):
                 self.assertEqual(vary_list[1][0], "num")
                 self.assertEqual(vary_list[0][0], "id")
                 self.assertEqual(2, len(vary_list))
@@ -65,18 +66,18 @@ class TestInitializeMethods(unittest.TestCase):
         with self.assertRaisesRegex(TypeError, "'parallel' is not a valid variable parameter"):
             init._validate_types(conf("bad4"))
 
-        with self.assertRaisesRegex(TypeError, "Varying parameters should be specified in a list"):
+        with self.assertRaisesRegex(TypeError, "Variable parameters should be specified in a list"):
             init._validate_types(conf("bad5"))
 
         with self.assertRaisesRegex(
             TypeError,
-            "value '0' of type <class 'int'> for key 'repeat' is not valid, must be a strictly positive integer",
+            "value '0' of type .*int.* for key 'repeat' is not valid, must be a strictly positive integer",
         ):
             init._validate_types(conf("bad6"))
 
         with self.assertRaisesRegex(
             ValueError,
-            r"Varying parameters lists should contain at least 1 element",
+            r"Variable parameters lists should contain at least 1 element",
         ):
             init._ensure_consistency(conf("bad7"))
 
@@ -92,7 +93,7 @@ class TestInitializeMethods(unittest.TestCase):
 
         with self.assertRaisesRegex(
             MissingParameterError,
-            r"1 of '\['peak_power', 'energy', 'width', 't0'\]' is required when 'soliton_num' is specified and no defaults have been set",
+            r"1 of '\['peak_power', 'mean_power', 'energy', 'width', 't0'\]' is required when 'soliton_num' is specified and no defaults have been set",
         ):
             init._ensure_consistency(conf("bad2"))
 
@@ -156,14 +157,49 @@ class TestInitializeMethods(unittest.TestCase):
             dict(
                 t_num=16384,
                 time_window=37e-12,
-                lower_wavelength_interp_limit=0,
-                upper_wavelength_interp_limit=1900e-9,
+                lower_wavelength_interp_limit=defaults.default_parameters[
+                    "lower_wavelength_interp_limit"
+                ],
+                upper_wavelength_interp_limit=defaults.default_parameters[
+                    "upper_wavelength_interp_limit"
+                ],
             ).items(),
             init._ensure_consistency(conf("good6"))["simulation"].items(),
         )
 
-    # def test_compute_init_parameters(self):
-    #     conf = lambda s: load_conf("compute_init_parameters/" + s)
+    def test_setup_custom_field(self):
+        d = np.load("testing/configs/custom_field/init_field.npz")
+        t = d["time"]
+        field = d["field"]
+        conf = load_conf("custom_field/no_change")
+        conf = init._generate_sim_grid(conf)
+        result = init.setup_custom_field(conf)
+        self.assertAlmostEqual(conf["field_0"].real.max(), field.real.max(), 4)
+        self.assertTrue(result)
+
+        conf = load_conf("custom_field/peak_power")
+        conf = init._generate_sim_grid(conf)
+        result = init.setup_custom_field(conf)
+        self.assertAlmostEqual(math.abs2(conf["field_0"]).max(), 20000, 4)
+        self.assertTrue(result)
+
+        conf = load_conf("custom_field/mean_power")
+        conf = init._generate_sim_grid(conf)
+        result = init.setup_custom_field(conf)
+        self.assertAlmostEqual(np.trapz(math.abs2(conf["field_0"]), conf["t"]), 0.22 / 40e6, 4)
+        self.assertTrue(result)
+
+        conf = load_conf("custom_field/recover1")
+        conf = init._generate_sim_grid(conf)
+        result = init.setup_custom_field(conf)
+        self.assertAlmostEqual(math.abs2(conf["field_0"] - field).sum(), 0)
+        self.assertTrue(result)
+
+        conf = load_conf("custom_field/recover2")
+        conf = init._generate_sim_grid(conf)
+        result = init.setup_custom_field(conf)
+        self.assertAlmostEqual((math.abs2(conf["field_0"]) / 0.9 - math.abs2(field)).sum(), 0)
+        self.assertTrue(result)
 
 
 if __name__ == "__main__":