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fix(mfusg): fix precision loss in CLN/GNC packages writing coordinates #2658

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Merged
wpbonelli merged 2 commits into from
Dec 4, 2025
Merged

fix(mfusg): fix precision loss in CLN/GNC packages writing coordinates #2658

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80c10a2
fix(mfusg): fix precision loss in CLN/GNC packages writing coordinates
reneangermeyer Nov 26, 2025
2c85e71
fix(mfusg): use high-precision format only when FREE format is enabled
reneangermeyer Dec 3, 2025
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11 changes: 9 additions & 2 deletions flopy/mfusg/mfusg.py
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Original file line number Diff line number Diff line change
Expand Up @@ -535,22 +535,29 @@ def _send_load_messages(model, files_successfully_loaded, files_not_loaded):
print(f" {os.path.basename(fname)}")


def fmt_string(array):
def fmt_string(array, free=False):
"""
Returns a C-style fmt string for numpy savetxt that corresponds to
the dtype.

Parameters
----------
array : numpy array
free : bool, optional
If True, use high-precision format (%16.9G) for floats which requires
FREE format in the BAS file. If False (default), use fixed 10-character
format (%10.2e) compatible with MODFLOW-USG's fixed-width input format.
"""
fmts = []
# When FREE format is enabled in BAS, we can use high-precision output.
# Without FREE, MODFLOW-USG expects 10-character fixed-width fields.
float_fmt = "%16.9G" if free else "%10.2e"
for field in array.dtype.descr:
vtype = field[1][1].lower()
if vtype in {"i", "b"}:
fmts.append("%10d")
elif vtype == "f":
fmts.append("%10.2e")
fmts.append(float_fmt)
elif vtype == "o":
fmts.append("%10s")
elif vtype == "s":
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13 changes: 9 additions & 4 deletions flopy/mfusg/mfusgcln.py
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Original file line number Diff line number Diff line change
Expand Up @@ -543,18 +543,23 @@ def write_file(self, f=None, check=False):
f_cln.write(self.iac_cln.get_file_entry())
f_cln.write(self.ja_cln.get_file_entry())

np.savetxt(f_cln, self.node_prop, fmt=fmt_string(self.node_prop), delimiter="")
free = self.parent.free_format_input
np.savetxt(
f_cln, self.node_prop, fmt=fmt_string(self.node_prop, free), delimiter=""
)

np.savetxt(f_cln, self.cln_gwc, fmt=fmt_string(self.cln_gwc), delimiter="")
np.savetxt(
f_cln, self.cln_gwc, fmt=fmt_string(self.cln_gwc, free), delimiter=""
)

if self.nconduityp > 0:
np.savetxt(
f_cln, self.cln_circ, fmt=fmt_string(self.cln_circ), delimiter=""
f_cln, self.cln_circ, fmt=fmt_string(self.cln_circ, free), delimiter=""
)

if self.nrectyp > 0:
np.savetxt(
f_cln, self.cln_rect, fmt=fmt_string(self.cln_rect), delimiter=""
f_cln, self.cln_rect, fmt=fmt_string(self.cln_rect, free), delimiter=""
)

f_cln.write(self.ibound.get_file_entry())
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