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Fix lost pivots in probabilistic linear algebra #370

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Merged
mohabsafey merged 3 commits into from
Oct 2, 2026
Merged

Fix lost pivots in probabilistic linear algebra #370

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1f857a5
Fix random multipliers in probabilistic linear algebra
wegank Oct 1, 2026
467ef28
Fix buffer overflow in probabilistic_sparse_dense_echelon_form_ff_32
wegank Oct 1, 2026
8658e15
Loop over blocks in probabilistic_dense_linear_algebra
wegank Oct 1, 2026
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1 change: 1 addition & 0 deletions Makefile.am
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,7 @@ check_PROGRAMS = neogb_io \
checkdiff = test/diff/diff_bug-2nd-prime-bad.sh \
test/diff/diff_bug-68.sh \
test/diff/diff_bug-empty-tracer.sh \
test/diff/diff_bug-prob-sparse-dense-la.sh \
test/diff/diff_cp-d3-n4-p2.sh \
test/diff/diff_cyclic5-16.sh \
test/diff/diff_cyclic5-31.sh \
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1 change: 1 addition & 0 deletions configure.ac
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Expand Up @@ -128,6 +128,7 @@ AC_CONFIG_LINKS([
input_files/bug-empty-tracer.ms:input_files/bug-empty-tracer.ms
output_files/bug-empty-tracer.g2.res:output_files/bug-empty-tracer.g2.res
test/diff/diff_bug-empty-tracer.sh:test/diff/diff_bug-empty-tracer.sh
test/diff/diff_bug-prob-sparse-dense-la.sh:test/diff/diff_bug-prob-sparse-dense-la.sh
input_files/choice-linear-form-qq.ms:input_files/choice-linear-form-qq.ms
output_files/choice-linear-form-qq.P2.d0.res:output_files/choice-linear-form-qq.P2.d0.res
output_files/choice-linear-form-qq.p128.res:output_files/choice-linear-form-qq.p128.res
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8 changes: 4 additions & 4 deletions src/neogb/la_ff_16.c
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Expand Up @@ -779,7 +779,7 @@ static void probabilistic_sparse_reduced_echelon_form_ff_16(
/* fill random value array */
for (j = 0; j < nrbl; ++j) {
do {
mull[j] = (int64_t)rand() & fc;
mull[j] = (int64_t)rand() % fc;
} while (mull[j] == 0);
}
/* generate one dense row as random linear combination
Expand Down Expand Up @@ -1660,7 +1660,7 @@ static cf16_t **probabilistic_dense_linear_algebra_ff_16(
#pragma omp parallel for num_threads(st->nthrds) \
private(i, j, k, l) shared(nps, tbr) \
schedule(dynamic)
for (i = 0; i < ntr; ++i) {
for (i = 0; i < nb; ++i) {
int64_t *drl = dr + (omp_get_thread_num() * (uint64_t)ncr);
int64_t *mull = mul + (omp_get_thread_num() * (uint64_t)rpb);
const int32_t nbl = (int32_t) (ntr > (i+1)*rpb ? (i+1)*rpb : ntr);
Expand All @@ -1678,7 +1678,7 @@ static cf16_t **probabilistic_dense_linear_algebra_ff_16(
/* fill random value array */
for (j = 0; j < nrbl; ++j) {
do {
mull[j] = (int64_t)rand() & fc;
mull[j] = (int64_t)rand() % fc;
} while (mull[j] == 0);
}
/* generate one dense row as random linear combination
Expand Down Expand Up @@ -1812,7 +1812,7 @@ static cf16_t **probabilistic_sparse_dense_echelon_form_ff_16(
/* fill random value array */
for (j = 0; j < nrbl; ++j) {
do {
mull[j] = (int64_t)rand() & fc;
mull[j] = (int64_t)rand() % fc;
} while (mull[j] == 0);
}
/* generate one dense row as random linear combination
Expand Down
8 changes: 4 additions & 4 deletions src/neogb/la_ff_32.c
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Expand Up @@ -187,7 +187,7 @@ static int is_kernel_trivial(
/* fill random value array */
for (i = 0; i < ncr; ++i) {
do {
mull[j] = (int64_t)rand() & fc;
mull[j] = (int64_t)rand() % fc;
} while (mull[j] == 0);
}
for (i = 0; i < sat->ld; ++i) {
Expand Down Expand Up @@ -3586,7 +3586,7 @@ static cf32_t **probabilistic_dense_linear_algebra_ff_32(
#pragma omp parallel for num_threads(st->nthrds) \
private(i, j, k, l) shared(nps, tbr) \
schedule(dynamic)
for (i = 0; i < ntr; ++i) {
for (i = 0; i < nb; ++i) {
int64_t *drl = dr + (omp_get_thread_num() * (uint64_t)ncr);
int64_t *mull = mul + (omp_get_thread_num() * (uint64_t)rpb);
const int32_t nbl = (int32_t) (ntr > (i+1)*rpb ? (i+1)*rpb : ntr);
Expand Down Expand Up @@ -3716,7 +3716,7 @@ static cf32_t **probabilistic_sparse_dense_echelon_form_ff_32(
int64_t *dr = (int64_t *)malloc(
(uint64_t)ncols * st->nthrds * sizeof(int64_t));
int64_t *mul = (int64_t *)malloc(
(uint64_t)ncols * st->nthrds * sizeof(int64_t));
(uint64_t)rpb * st->nthrds * sizeof(int64_t));

/* reduction process to get all possible pivots, no interreduction here */
#pragma omp parallel for num_threads(st->nthrds) \
Expand All @@ -3738,7 +3738,7 @@ static cf32_t **probabilistic_sparse_dense_echelon_form_ff_32(
/* fill random value array */
for (j = 0; j < nrbl; ++j) {
do {
mull[j] = (int64_t)rand() & fc;
mull[j] = (int64_t)rand() % fc;
} while (mull[j] == 0);
}
/* generate one dense row as random linear combination
Expand Down
8 changes: 4 additions & 4 deletions src/neogb/la_ff_8.c
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Original file line number Diff line number Diff line change
Expand Up @@ -928,7 +928,7 @@ static void probabilistic_sparse_reduced_echelon_form_ff_8(
/* fill random value array */
for (j = 0; j < nrbl; ++j) {
do {
mull[j] = (int64_t)rand() & fc;
mull[j] = (int64_t)rand() % fc;
} while (mull[j] == 0);
}
/* generate one dense row as random linear combination
Expand Down Expand Up @@ -1789,7 +1789,7 @@ static cf8_t **probabilistic_dense_linear_algebra_ff_8(
#pragma omp parallel for num_threads(st->nthrds) \
private(i, j, k, l) shared(nps, tbr) \
schedule(dynamic)
for (i = 0; i < ntr; ++i) {
for (i = 0; i < nb; ++i) {
int64_t *drl = dr + (omp_get_thread_num() * (uint64_t)ncr);
int64_t *mull = mul + (omp_get_thread_num() * (uint64_t)rpb);
const int32_t nbl = (int32_t) (ntr > (i+1)*rpb ? (i+1)*rpb : ntr);
Expand All @@ -1807,7 +1807,7 @@ static cf8_t **probabilistic_dense_linear_algebra_ff_8(
/* fill random value array */
for (j = 0; j < nrbl; ++j) {
do {
mull[j] = (int64_t)rand() & fc;
mull[j] = (int64_t)rand() % fc;
} while (mull[j] == 0);
}
/* generate one dense row as random linear combination
Expand Down Expand Up @@ -1941,7 +1941,7 @@ static cf8_t **probabilistic_sparse_dense_echelon_form_ff_8(
/* fill random value array */
for (j = 0; j < nrbl; ++j) {
do {
mull[j] = (int64_t)rand() & fc;
mull[j] = (int64_t)rand() % fc;
} while (mull[j] == 0);
}
/* generate one dense row as random linear combination
Expand Down
36 changes: 36 additions & 0 deletions test/diff/diff_bug-prob-sparse-dense-la.sh
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Original file line number Diff line number Diff line change
@@ -0,0 +1,36 @@
#!/usr/bin/env bash

# Probabilistic sparse/dense linear algebra (-l 42) used to lose rows on
# small matrices since the random multipliers were not uniformly chosen
# in [1, p-1]. Then msolve wrote an empty output file while exiting with
# status 0. The failure depends on the random seed, thus we run several
# consecutive seeds. Line 5 of the output (the random linear form) depends
# on the seed and is not compared.

file=nonradical-radicalshape-31

source test/diff/diff_source.sh

sed 5d output_files/$file.res > test/diff/$file.prob-la.ref

for i in $(seq 0 39); do
for t in 1 2; do
$(pwd)/msolve -f input_files/$file.ms -o test/diff/$file.prob-la.res \
--random-seed $((seed + i)) -P 1 -l 42 -t $t
if [ $? -gt 0 ]; then
print_exit 1
fi

sed 5d test/diff/$file.prob-la.res | \
diff - test/diff/$file.prob-la.ref
if [ $? -gt 0 ]; then
print_exit 2
fi

rm test/diff/$file.prob-la.res
done
done

rm test/diff/$file.prob-la.ref

normal_exit
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