Skip to content
New issue

Have a question about this project? # for a free GitHub account to open an issue and contact its maintainers and the community.

#

By clicking “#”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? # to your account

Fix primality test for very small numbers #102

Open
wants to merge 5 commits into
base: main
Choose a base branch
from
Open

Fix primality test for very small numbers #102

Show file tree
Hide file tree
Changes from 1 commit
Commits
Show all changes
5 commits
Select commit Hold shift + click to select a range
01badcb
Fix primality test for very small numbers
rostislav Jan 14, 2022
bf94b76
Refactor Makefile to avoid repetition
rostislav Jan 21, 2022
db5127a
Add a test of correctness of BPSW primality test
rostislav Jan 25, 2022
ce2de95
Add primes_test to CI
rostislav Jan 25, 2022
721903a
Use VDF_ASSERT macro in 1weso_test.cpp
rostislav Jan 25, 2022
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
2 changes: 2 additions & 0 deletions src/pprods.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -386,4 +386,6 @@ static const uint64_t pprods[] = {
0xaf157a9999de1f, // 14887*14891*14897*14923
0xb1110edec9a5e7, // 14929*14939*14947*14951
};

static const uint32_t pprods_max_prime = 14951;
#endif // PPRODS_H
19 changes: 14 additions & 5 deletions src/primetest.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -141,9 +141,10 @@ static int is_prime_bpsw(const mpz_t n)
int min_pprods = 5, n_pprods = sizeof(pprods) / sizeof(*pprods);
mpz_t b, d;

/* Discard even numbers. */
if (!mpz_tstbit(n, 0) && mpz_cmp_ui(n, 2))
return 0;
/* Discard even and non-positive numbers. */
if (!mpz_tstbit(n, 0) || n->_mp_size < 1) {
return mpz_cmp_ui(n, 2) ? 0 : 2;
}

/* Adjust the number of GCDs to compute with products of small primes
* if bit length of n is less than 1024. As the computational cost of
Expand All @@ -155,8 +156,16 @@ static int is_prime_bpsw(const mpz_t n)
}

for (i = 0; i < n_pprods; i++) {
if (mpn_gcd_1(n->_mp_d, n->_mp_size, pprods[i]) != 1)
return 0;
if (mpn_gcd_1(n->_mp_d, n->_mp_size, pprods[i]) != 1) {
if (n->_mp_size > 1 || n->_mp_d[0] > pprods_max_prime) {
return 0;
} else if (n->_mp_d[0] < 8) {
/* Special case for primes 3, 5, 7. */
return (1 << n->_mp_d[0]) & 0xac ? 2 : 0;
} else {
break;
}
}
}

mpz_init2(b, n->_mp_size * sizeof(n->_mp_d[0]) * 8);
Expand Down
4 changes: 3 additions & 1 deletion tools/gen_pprods.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -73,6 +73,8 @@ def print_pprods_h(prods, factors):
static const uint64_t pprods[] = {
%s
};

static const uint32_t pprods_max_prime = %d;
#endif // PPRODS_H
"""
tmpl = tmpl.strip()
Expand All @@ -81,7 +83,7 @@ def print_pprods_h(prods, factors):
factors_str = "*".join(map(str, factors[i]))
extra_spaces = " " * (16 - (pr.bit_length() + 3) // 4)
prods_str += tab + "0x%x, %s// %s\n" % (pr, extra_spaces, factors_str)
print(tmpl % (prods_str.rstrip(),))
print(tmpl % (prods_str.rstrip(), factors[-1][-1]))


n = int(sys.argv[1])
Expand Down