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Fix edge case in phase_single_det and phase_double_det #114

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Fix edge case in phase_single_det and phase_double_det #114

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41 changes: 21 additions & 20 deletions pyci/src/common.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -152,6 +152,14 @@ void unrank_colex(long nbasis, const long nocc, long rank, long *occs) {
}
}

inline ulong mask_above(long n) {
return (n >= Size<ulong>() - 1) ? 0UL : ~( (1UL << (n + 1)) - 1 );
}

inline ulong mask_below(long m) {
return (m >= Size<ulong>()) ? Max<ulong>() : (1UL << m) - 1;
}

long phase_single_det(const long nword, const long i, const long a, const ulong *det) {
(void)nword; // nword is deliberately unused.
long j, k, l, m, n, high, low, nperm = 0;
Expand All @@ -168,21 +176,18 @@ long phase_single_det(const long nword, const long i, const long a, const ulong
j = low / Size<ulong>();
n = low % Size<ulong>();
mask = det[j];
mask &= Max<ulong>();
if (j == k) {
mask &= (1UL << m) - 1;
mask &= ~(1UL << (n + 1)) + 1;
mask &= mask_below(m);
mask &= mask_above(n);
nperm += Pop(mask);
} else {
mask &= ~(1UL << (n + 1)) + 1;
mask &= mask_above(n);
nperm += Pop(mask);
mask = det[k];
mask &= (1UL << m) - 1;
mask &= mask_below(m);
nperm += Pop(mask);
for (l = j + 1; l < k; ++l) {
mask = det[l];
mask &= Max<ulong>();
nperm += Pop(mask);
nperm += Pop(det[l]);
}
}
return (nperm % 2) ? -1 : 1;
Expand All @@ -206,20 +211,18 @@ long phase_double_det(const long nword, const long i1, const long i2, const long
j = low / Size<ulong>();
n = low % Size<ulong>();
mask = det[j];
mask &= Max<ulong>();
if (j == k) {
mask &= (1UL << m) - 1;
mask &= ~(1UL << (n + 1)) + 1;
mask &= mask_below(m);
mask &= mask_above(n);
nperm += Pop(mask);
} else {
mask &= ~(1UL << (n + 1)) + 1;
mask &= mask_above(n);
nperm += Pop(mask);
mask = det[k];
mask &= (1UL << m) - 1;
mask &= mask_below(m);
nperm += Pop(mask);
for (l = j + 1; l < k; ++l) {
mask = det[l];
mask &= Max<ulong>();
nperm += Pop(mask);
}
}
Expand All @@ -236,20 +239,18 @@ long phase_double_det(const long nword, const long i1, const long i2, const long
j = low / Size<ulong>();
n = low % Size<ulong>();
mask = det[j];
mask &= Max<ulong>();
if (j == k) {
mask &= (1UL << m) - 1;
mask &= ~(1UL << (n + 1)) + 1;
mask &= mask_below(m);
mask &= mask_above(n);
nperm += Pop(mask);
} else {
mask &= ~(1UL << (n + 1)) + 1;
mask &= mask_above(n);
nperm += Pop(mask);
mask = det[k];
mask &= (1UL << m) - 1;
mask &= mask_below(m);
nperm += Pop(mask);
for (l = j + 1; l < k; ++l) {
mask = det[l];
mask &= Max<ulong>();
nperm += Pop(mask);
}
}
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