[Code scan] Avoid mutating CP2K default_config across input generations

[njzjz]

This issue is from a Codex global scan of the repository.

CP2K input generation mutates the module-level default_config, so settings from one generated input can leak into later inputs in the same Python process.

Evidence:

dpgen/dpgen/generator/lib/cp2k.py

Lines 125 to 152 in 7af5246

	default_config = {
	"GLOBAL": {"PROJECT": "DPGEN"},
	"FORCE_EVAL": {
	"METHOD": "QS",
	"STRESS_TENSOR": "ANALYTICAL",
	"DFT": {
	"BASIS_SET_FILE_NAME": "./cp2k_basis_pp_file/BASIS_MOLOPT",
	"POTENTIAL_FILE_NAME": "./cp2k_basis_pp_file/GTH_POTENTIALS",
	"CHARGE": 0,
	"UKS": "F",
	"MULTIPLICITY": 1,
	"MGRID": {"CUTOFF": 400, "REL_CUTOFF": 50, "NGRIDS": 4},
	"QS": {"EPS_DEFAULT": "1.0E-12"},
	"SCF": {"SCF_GUESS": "ATOMIC", "EPS_SCF": "1.0E-6", "MAX_SCF": 50},
	"XC": {"XC_FUNCTIONAL": {"_": "PBE"}},
	},
	"SUBSYS": {
	"CELL": {"A": "10 .0 .0", "B": ".0 10 .0", "C": ".0 .0 10"},
	"COORD": {"@include": "coord.xyz"},
	"KIND": {
	"_": ["H", "C", "N"],
	"POTENTIAL": ["GTH-PBE-q1", "GTH-PBE-q4", "GTH-PBE-q5"],
	"BASIS_SET": ["DZVP-MOLOPT-GTH", "DZVP-MOLOPT-GTH", "DZVP-MOLOPT-GTH"],
	},
	},
	"PRINT": {"FORCES": {"_": "ON"}, "STRESS_TENSOR": {"_": "ON"}},
	},
	}

dpgen/dpgen/generator/lib/cp2k.py

Lines 155 to 170 in 7af5246

	def update_dict(old_d, update_d):
	"""A method to recursive update dict
	:old_d: old dictionary
	:update_d: some update value written in dictionary form.
	"""
	import collections.abc
	for k, v in update_d.items():
	if (
	k in old_d
	and isinstance(old_d[k], dict)
	and isinstance(update_d[k], collections.abc.Mapping)
	):
	update_dict(old_d[k], update_d[k])
	else:
	old_d[k] = update_d[k]

dpgen/dpgen/generator/lib/cp2k.py

Lines 307 to 321 in 7af5246

	# get update from user
	user_config = fp_params
	# get update from cell
	cell_config = {
	"FORCE_EVAL": {"SUBSYS": {"CELL": {"A": cell_a, "B": cell_b, "C": cell_c}}}
	}
	# get update for multiplicity
	multiplicity_config = {"FORCE_EVAL": {"DFT": {"MULTIPLICITY": multiplicity}}}
	update_dict(default_config, user_config)
	update_dict(default_config, cell_config)
	update_dict(default_config, multiplicity_config)
	# output list
	input_str = []
	iterdict(default_config, input_str)
	string = "\n".join(input_str)

update_dict() mutates its first argument in place, and make_cp2k_input() calls it directly on the module global default_config. Any user override, generated cell, or multiplicity value remains in default_config for the next call unless overwritten again.

Expected behavior: each make_cp2k_input() call should start from a deep copy of default_config before applying user and structure-specific updates.