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Raised upper limit for Comba squaring #502

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Merged
merged 2 commits into from
Apr 5, 2023
Merged

Raised upper limit for Comba squaring #502

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b1e1ea5
Raised upper limit for Comba squaring
czurnieden Jan 7, 2021
3d79350
Addition of extensive tests for s_mp_sqr_comba
czurnieden Jan 7, 2021
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47 changes: 47 additions & 0 deletions demo/test.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1828,6 +1828,51 @@ static int test_mp_root_n(void)
return EXIT_FAILURE;
}

/* Less error-prone than -1 + 2^n with mp_2expt */
static mp_err s_fill_with_ones(mp_int *a, int size)
{
int i;
mp_err err = MP_OKAY;

mp_zero(a);

if ((err = mp_grow(a, size)) != MP_OKAY) goto LTM_ERR;
for (i = 0; i < size; i++) {
a->dp[i] = (mp_digit)MP_MASK;
a->used++;
}

LTM_ERR:
return err;
}

static int test_s_mp_sqr_comba(void)
{
mp_int a, r1, r2;
int i, j;

DOR(mp_init_multi(&a, &r1, &r2, NULL));

for (i = 1; i <= MP_MAX_COMBA; i++) {
DO(s_fill_with_ones(&a, i));
DO(s_mp_sqr_comba(&a, &r1));
DO(s_mp_sqr(&a, &r2));
EXPECT(mp_cmp(&r1, &r2) == MP_EQ);
for (j = 0; j < 20; j++) {
DO(mp_rand(&a, i));
DO(s_mp_sqr_comba(&a, &r1));
DO(s_mp_sqr(&a, &r2));
EXPECT(mp_cmp(&r1, &r2) == MP_EQ);
}
}

mp_clear_multi(&a, &r1, &r2, NULL);
return EXIT_SUCCESS;
LBL_ERR:
mp_clear_multi(&a, &r1, &r2, NULL);
return EXIT_FAILURE;
}

static int test_s_mp_mul_balance(void)
{
mp_int a, b, c;
Expand Down Expand Up @@ -2328,6 +2373,8 @@ static int unit_tests(int argc, char **argv)
T1(mp_xor, MP_XOR),
T3(s_mp_div_recursive, ONLY_PUBLIC_API, S_MP_DIV_RECURSIVE, S_MP_DIV_SCHOOL),
T3(s_mp_div_small, ONLY_PUBLIC_API, S_MP_DIV_SMALL, S_MP_DIV_SCHOOL),
/* s_mp_mul_comba not (yet) testable because s_mp_mul branches to s_mp_mul_comba automatically */
T2(s_mp_sqr_comba, ONLY_PUBLIC_API, S_MP_SQR_COMBA),
T2(s_mp_mul_balance, ONLY_PUBLIC_API, S_MP_MUL_BALANCE),
T2(s_mp_mul_karatsuba, ONLY_PUBLIC_API, S_MP_MUL_KARATSUBA),
T2(s_mp_sqr_karatsuba, ONLY_PUBLIC_API, S_MP_SQR_KARATSUBA),
Expand Down
2 changes: 1 addition & 1 deletion mp_mul.c
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Original file line number Diff line number Diff line change
Expand Up @@ -23,7 +23,7 @@ mp_err mp_mul(const mp_int *a, const mp_int *b, mp_int *c)
} else if ((a == b) &&
MP_HAS(S_MP_SQR_COMBA) && /* can we use the fast comba multiplier? */
(((a->used * 2) + 1) < MP_WARRAY) &&
(a->used < (MP_MAX_COMBA / 2))) {
(a->used <= MP_MAX_COMBA)) {
err = s_mp_sqr_comba(a, c);
} else if ((a == b) &&
MP_HAS(S_MP_SQR)) {
Expand Down