def to_fci(cisdvec, nelec, orbspin):
from pyscf import fci
nocc = nelec
norb = len(orbspin)
c0, c1, c2 = cisdvec_to_amplitudes(cisdvec, nocc, norb - nocc)
oidxa = orbspin[:nocc] == 0
oidxb = orbspin[:nocc] == 1
vidxa = orbspin[nocc:] == 0
vidxb = orbspin[nocc:] == 1
c1a = c1[oidxa][:, vidxa]
c1b = c1[oidxb][:, vidxb]
c2aa = c2[oidxa][:, oidxa][:, :, vidxa][:, :, :, vidxa]
c2bb = c2[oidxb][:, oidxb][:, :, vidxb][:, :, :, vidxb]
c2ab = c2[oidxa][:, oidxb][:, :, vidxa][:, :, :, vidxb]
nocca = numpy.count_nonzero(oidxa)
noccb = numpy.count_nonzero(oidxb)
nvira = numpy.count_nonzero(vidxa)
nvirb = numpy.count_nonzero(vidxb)
norba = nocca + nvira
norbb = noccb + nvirb
t1addra, t1signa = t1strs(norba, nocca)
t1addrb, t1signb = t1strs(norbb, noccb)
na = fci.cistring.num_strings(norba, nocca)
nb = fci.cistring.num_strings(norbb, noccb)
fcivec = numpy.zeros((na, nb))
fcivec[0, 0] = c0
fcivec[t1addra, 0] = c1a[::-1].T.ravel() * t1signa
fcivec[0, t1addrb] = c1b[::-1].T.ravel() * t1signb
c2ab = c2ab[::-1, ::-1].transpose(2, 0, 3, 1).reshape(nocca * nvira, -1)
c2ab = numpy.einsum('i,j,ij->ij', t1signa, t1signb, c2ab)
lib.takebak_2d(fcivec, c2ab, t1addra, t1addrb)
if nocca > 1 and nvira > 1:
ooidx = numpy.tril_indices(nocca, -1)
vvidx = numpy.tril_indices(nvira, -1)
c2aa = c2aa[ooidx][:, vvidx[0], vvidx[1]]
t2addra, t2signa = t2strs(norba, nocca)
fcivec[t2addra, 0] = c2aa[::-1].T.ravel() * t2signa
if noccb > 1 and nvirb > 1:
ooidx = numpy.tril_indices(noccb, -1)
vvidx = numpy.tril_indices(nvirb, -1)
c2bb = c2bb[ooidx][:, vvidx[0], vvidx[1]]
t2addrb, t2signb = t2strs(norbb, noccb)
fcivec[0, t2addrb] = c2bb[::-1].T.ravel() * t2signb
return fcivec
def from_fci(ci0, nelec, orbspin):
from pyscf.cc.addons import spatial2spin
nocc = nelec
oidxa = orbspin[:nocc] == 0
oidxb = orbspin[:nocc] == 1
vidxa = orbspin[nocc:] == 0
vidxb = orbspin[nocc:] == 1
nocca = numpy.count_nonzero(oidxa)
noccb = numpy.count_nonzero(oidxb)
nvira = numpy.count_nonzero(vidxa)
nvirb = numpy.count_nonzero(vidxb)
norba = nocca + nvira
norbb = noccb + nvirb
t1addra, t1signa = t1strs(norba, nocca)
t1addrb, t1signb = t1strs(norbb, noccb)
na = fci.cistring.num_strings(norba, nocca)
nb = fci.cistring.num_strings(norbb, noccb)
ci0 = ci0.reshape(na, nb)
c0 = ci0[0, 0]
c1a = ((ci0[t1addra, 0] * t1signa).reshape(nvira, nocca).T)[::-1]
c1b = ((ci0[0, t1addrb] * t1signb).reshape(nvirb, noccb).T)[::-1]
c1 = spatial2spin((c1a, c1b), orbspin)
c2ab = numpy.einsum('i,j,ij->ij', t1signa, t1signb, ci0[t1addra][:,
t1addrb])
c2ab = c2ab.reshape(nvira, nocca, nvirb, noccb).transpose(1, 3, 0, 2)
c2ab = c2ab[::-1, ::-1]
t2addra, t2signa = t2strs(norba, nocca)
c2aa = (ci0[t2addra, 0] * t2signa).reshape(nvira * (nvira - 1) // 2, -1).T
c2aa = _unpack_4fold(c2aa[::-1], nocca, nvira)
t2addrb, t2signb = t2strs(norbb, noccb)
c2bb = (ci0[0, t2addrb] * t2signb).reshape(nvirb * (nvirb - 1) // 2, -1).T
c2bb = _unpack_4fold(c2bb[::-1], noccb, nvirb)
c2 = spatial2spin((c2aa, c2ab, c2bb), orbspin)
cisdvec = amplitudes_to_cisdvec(c0, c1, c2)
return cisdvec