Manually constructing the grid can lead to failed calculations

[awvwgk]

Since the grid needs to be constructed as unsorted grid for Skala-1.1, constructing the grid manually without specifying sort_grids=False can lead to failed calculations. We should either document this behavior explicitly or have a better way to intercept a sorted grid before it reaches the XC integrator and fails with an obscure error message.

Example:

In [1]: from pyscf import gto
   ...: from skala.gpu4pyscf import SkalaKS

In [2]: mol = gto.M(atom="H 0 0 0; H 0 0 1.1", basis="def2-svp")

In [3]: ks = SkalaKS(mol, xc="skala-1.1")

In [4]: ks.grids.build()  # Create sorted grid by default
Out[4]: <gpu4pyscf.dft.gen_grid.Grids at 0x7f658a242660>

In [5]: ks.kernel()
---------------------------------------------------------------------------
LinAlgError                               Traceback (most recent call last)
Cell In[5], line 1
----> 1 ks.kernel()

File $PREFIX/lib/python3.13/site-packages/gpu4pyscf/scf/hf.py:355, in scf(mf, dm0, **kwargs)
    350     dm0 = mf.make_rdm1()
    352 if mf.max_cycle > 0 or mf.mo_coeff is None:
    353     mf.converged, mf.e_tot, \
    354             mf.mo_energy, mf.mo_coeff, mf.mo_occ = \
--> 355             _kernel(mf, mf.conv_tol, mf.conv_tol_grad,
    356                     dm0=dm0, callback=mf.callback,
    357                     conv_check=mf.conv_check, **kwargs)
    358 else:
    359     # Avoid to update SCF orbitals in the non-SCF initialization
    360     # (issue #495).  But run regular SCF for initial guess if SCF was
    361     # not initialized.
    362     mf.e_tot = _kernel(mf, mf.conv_tol, mf.conv_tol_grad,
    363                         dm0=dm0, callback=mf.callback,
    364                         conv_check=mf.conv_check, **kwargs)[1]

File $PREFIX/lib/python3.13/site-packages/gpu4pyscf/scf/hf.py:260, in _kernel(mf, conv_tol, conv_tol_grad, dump_chk, dm0, callback, conv_check, **kwargs)
    257 dm_last = dm
    258 last_hf_e = e_tot
--> 260 fock = mf.get_fock(h1e, s1e, vhf, dm, cycle, mf_diis, fock_last=fock_last)
    261 t1 = log.timer_debug1('DIIS', *t0)
    262 mo_energy, mo_coeff = mf.eig(fock, s1e)

File $PREFIX/lib/python3.13/site-packages/gpu4pyscf/scf/hf.py:160, in get_fock(mf, h1e, s1e, vhf, dm, cycle, diis, diis_start_cycle, level_shift_factor, damp_factor, fock_last)
    158     f = damping(f, fock_last, damp_factor)
    159 if diis is not None and cycle >= diis_start_cycle:
--> 160     f = diis.update(s1e, dm, f)
    162 if level_shift_factor is None:
    163     level_shift_factor = mf.level_shift

File $PREFIX/lib/python3.13/site-packages/gpu4pyscf/scf/diis.py:67, in CDIIS.update(self, s, d, f, *args, **kwargs)
     65 errvec = pack_tril(errvec.reshape(-1,nmo,nmo))
     66 f_tril = pack_tril(f.reshape(-1,nao,nao))
---> 67 xnew = lib.diis.DIIS.update(self, f_tril, xerr=errvec)
     68 if self.rollback > 0 and len(self._bookkeep) == self.space:
     69     self._bookkeep = self._bookkeep[-self.rollback:]

File $PREFIX/lib/python3.13/site-packages/gpu4pyscf/lib/diis.py:211, in DIIS.update(self, x, xerr)
    208 dt = None
    210 if self._xprev is None:
--> 211     xnew = cupy.asarray(self.extrapolate(nd))
    212 else:
    213     self._xprev = None # release memory first

File $PREFIX/lib/python3.13/site-packages/gpu4pyscf/lib/diis.py:229, in DIIS.extrapolate(self, nd)
    226 g = np.zeros(nd+1, h.dtype)
    227 g[0] = 1
--> 229 w, v = np.linalg.eigh(h)
    230 if any(abs(w)<1e-14):
    231     logger.debug(self, 'Linear dependence found in DIIS error vectors.')

File $PREFIX/lib/python3.13/site-packages/numpy/linalg/_linalg.py:1677, in eigh(a, UPLO)
   1673 signature = 'D->dD' if isComplexType(t) else 'd->dd'
   1674 with errstate(call=_raise_linalgerror_eigenvalues_nonconvergence,
   1675               invalid='call', over='ignore', divide='ignore',
   1676               under='ignore'):
-> 1677     w, vt = gufunc(a, signature=signature)
   1678 w = w.astype(_realType(result_t), copy=False)
   1679 vt = vt.astype(result_t, copy=False)

File $PREFIX/lib/python3.13/site-packages/numpy/linalg/_linalg.py:169, in _raise_linalgerror_eigenvalues_nonconvergence(err, flag)
    168 def _raise_linalgerror_eigenvalues_nonconvergence(err, flag):
--> 169     raise LinAlgError("Eigenvalues did not converge")

LinAlgError: Eigenvalues did not converge