Read NBANDS in io.vasp.outputs.Outcar init

[DanielYang59]

Summary

• Read NBANDS in io.vasp.outputs.Outcar init, to close Support parsing of NBANDS from a VASP OUTCAR file #3843
• Add overwriting tests and test file (355 KB), I didn't find any reusable file (zgrep 'I found NBANDS' OUTCAR* returns nothing)

VASP version stability

• 5.2.11 (unit test)
• 5.4.4 (unit test)
• 6.3.0 (unit test)
• 6.3.2 (unit test, overridden)

Reason for using current pattern instead of NBANDS = (\d+)

As mentioned in #3843 (comment), the NBANDS could be modified to be "number of cores compatible". More specifically:

When executed on multiple CPUs, VASP automatically increases the number of bands, so that NBANDS is divisible by the number of CPU cores. If NCORE > 1, NBANDS is increased until it is divisible by the number of cores in a group (NCORE). If KPAR > 1, NBANDS is increased until it is divisible by the number of cores in a group.

For example if I set NBANDS to 30 on a 64-core job, it would be modified to 32 with the following message:

>>> grep NBANDS OUTCAR_set_30_but_changed_to_32 
   NBANDS = 30
|     I found NBANDS = 30. Now, NBANDS = 32.                                  |
   k-points           NKPTS =    126   k-points in BZ     NKDIM =    126   number of bands    NBANDS=     32

[DanielYang59]

Question

Why would the "total number of plane waves (NPLWV)" value take a nested list format (added in #1757)?

pymatgen/src/pymatgen/io/vasp/outputs.py

Lines 2139 to 2147 in 31f1e1f

	# Read "total number of plane waves", NPLWV:
	self.read_pattern(
	{"nplwv": r"total plane-waves NPLWV =\s+(\*{6}|\d+)"},
	terminate_on_match=True,
	)
	try:
	self.data["nplwv"] = [[int(self.data["nplwv"][0][0])]]
	except ValueError:
	self.data["nplwv"] = [[None]]

pymatgen/tests/io/vasp/test_outputs.py

Lines 1330 to 1332 in 31f1e1f

	def test_nplwvs(self):
	outcar = Outcar(f"{VASP_OUT_DIR}/OUTCAR.gz")
	assert outcar.data["nplwv"] == [[34560]]

[DanielYang59]

@Andrew-S-Rosen Is currently implementation looking good to you? :)

[Andrew-S-Rosen]

Due to time commitments, I can just say that I trust you. 👍 Happy to report if something comes up.

[DanielYang59]

Thanks for saying that, I tested on multiple VASP versions (included in unit test) and didn't find any issue for now, do let me know if you notice any :)