diff options
Diffstat (limited to 'libtommath/bn_mp_karatsuba_mul.c')
| -rw-r--r-- | libtommath/bn_mp_karatsuba_mul.c | 278 |
1 files changed, 141 insertions, 137 deletions
diff --git a/libtommath/bn_mp_karatsuba_mul.c b/libtommath/bn_mp_karatsuba_mul.c index 4d982c7..41b7bfa 100644 --- a/libtommath/bn_mp_karatsuba_mul.c +++ b/libtommath/bn_mp_karatsuba_mul.c @@ -1,4 +1,4 @@ -#include <tommath_private.h> +#include "tommath_private.h" #ifdef BN_MP_KARATSUBA_MUL_C /* LibTomMath, multiple-precision integer library -- Tom St Denis * @@ -9,159 +9,163 @@ * Michael Fromberger but has been written from scratch with * additional optimizations in place. * - * The library is free for all purposes without any express - * guarantee it works. - * - * Tom St Denis, tstdenis82@gmail.com, http://libtom.org + * SPDX-License-Identifier: Unlicense */ -/* c = |a| * |b| using Karatsuba Multiplication using +/* c = |a| * |b| using Karatsuba Multiplication using * three half size multiplications * - * Let B represent the radix [e.g. 2**DIGIT_BIT] and - * let n represent half of the number of digits in + * Let B represent the radix [e.g. 2**DIGIT_BIT] and + * let n represent half of the number of digits in * the min(a,b) * * a = a1 * B**n + a0 * b = b1 * B**n + b0 * - * Then, a * b => + * Then, a * b => a1b1 * B**2n + ((a1 + a0)(b1 + b0) - (a0b0 + a1b1)) * B + a0b0 * - * Note that a1b1 and a0b0 are used twice and only need to be - * computed once. So in total three half size (half # of - * digit) multiplications are performed, a0b0, a1b1 and + * Note that a1b1 and a0b0 are used twice and only need to be + * computed once. So in total three half size (half # of + * digit) multiplications are performed, a0b0, a1b1 and * (a1+b1)(a0+b0) * * Note that a multiplication of half the digits requires - * 1/4th the number of single precision multiplications so in - * total after one call 25% of the single precision multiplications - * are saved. Note also that the call to mp_mul can end up back - * in this function if the a0, a1, b0, or b1 are above the threshold. - * This is known as divide-and-conquer and leads to the famous - * O(N**lg(3)) or O(N**1.584) work which is asymptopically lower than - * the standard O(N**2) that the baseline/comba methods use. - * Generally though the overhead of this method doesn't pay off + * 1/4th the number of single precision multiplications so in + * total after one call 25% of the single precision multiplications + * are saved. Note also that the call to mp_mul can end up back + * in this function if the a0, a1, b0, or b1 are above the threshold. + * This is known as divide-and-conquer and leads to the famous + * O(N**lg(3)) or O(N**1.584) work which is asymptopically lower than + * the standard O(N**2) that the baseline/comba methods use. + * Generally though the overhead of this method doesn't pay off * until a certain size (N ~ 80) is reached. */ -int mp_karatsuba_mul (mp_int * a, mp_int * b, mp_int * c) +int mp_karatsuba_mul(const mp_int *a, const mp_int *b, mp_int *c) { - mp_int x0, x1, y0, y1, t1, x0y0, x1y1; - int B, err; - - /* default the return code to an error */ - err = MP_MEM; - - /* min # of digits */ - B = MIN (a->used, b->used); - - /* now divide in two */ - B = B >> 1; - - /* init copy all the temps */ - if (mp_init_size (&x0, B) != MP_OKAY) - goto ERR; - if (mp_init_size (&x1, a->used - B) != MP_OKAY) - goto X0; - if (mp_init_size (&y0, B) != MP_OKAY) - goto X1; - if (mp_init_size (&y1, b->used - B) != MP_OKAY) - goto Y0; - - /* init temps */ - if (mp_init_size (&t1, B * 2) != MP_OKAY) - goto Y1; - if (mp_init_size (&x0y0, B * 2) != MP_OKAY) - goto T1; - if (mp_init_size (&x1y1, B * 2) != MP_OKAY) - goto X0Y0; - - /* now shift the digits */ - x0.used = y0.used = B; - x1.used = a->used - B; - y1.used = b->used - B; - - { - int x; - mp_digit *tmpa, *tmpb, *tmpx, *tmpy; - - /* we copy the digits directly instead of using higher level functions - * since we also need to shift the digits - */ - tmpa = a->dp; - tmpb = b->dp; - - tmpx = x0.dp; - tmpy = y0.dp; - for (x = 0; x < B; x++) { - *tmpx++ = *tmpa++; - *tmpy++ = *tmpb++; - } - - tmpx = x1.dp; - for (x = B; x < a->used; x++) { - *tmpx++ = *tmpa++; - } - - tmpy = y1.dp; - for (x = B; x < b->used; x++) { - *tmpy++ = *tmpb++; - } - } - - /* only need to clamp the lower words since by definition the - * upper words x1/y1 must have a known number of digits - */ - mp_clamp (&x0); - mp_clamp (&y0); - - /* now calc the products x0y0 and x1y1 */ - /* after this x0 is no longer required, free temp [x0==t2]! */ - if (mp_mul (&x0, &y0, &x0y0) != MP_OKAY) - goto X1Y1; /* x0y0 = x0*y0 */ - if (mp_mul (&x1, &y1, &x1y1) != MP_OKAY) - goto X1Y1; /* x1y1 = x1*y1 */ - - /* now calc x1+x0 and y1+y0 */ - if (s_mp_add (&x1, &x0, &t1) != MP_OKAY) - goto X1Y1; /* t1 = x1 - x0 */ - if (s_mp_add (&y1, &y0, &x0) != MP_OKAY) - goto X1Y1; /* t2 = y1 - y0 */ - if (mp_mul (&t1, &x0, &t1) != MP_OKAY) - goto X1Y1; /* t1 = (x1 + x0) * (y1 + y0) */ - - /* add x0y0 */ - if (mp_add (&x0y0, &x1y1, &x0) != MP_OKAY) - goto X1Y1; /* t2 = x0y0 + x1y1 */ - if (s_mp_sub (&t1, &x0, &t1) != MP_OKAY) - goto X1Y1; /* t1 = (x1+x0)*(y1+y0) - (x1y1 + x0y0) */ - - /* shift by B */ - if (mp_lshd (&t1, B) != MP_OKAY) - goto X1Y1; /* t1 = (x0y0 + x1y1 - (x1-x0)*(y1-y0))<<B */ - if (mp_lshd (&x1y1, B * 2) != MP_OKAY) - goto X1Y1; /* x1y1 = x1y1 << 2*B */ - - if (mp_add (&x0y0, &t1, &t1) != MP_OKAY) - goto X1Y1; /* t1 = x0y0 + t1 */ - if (mp_add (&t1, &x1y1, c) != MP_OKAY) - goto X1Y1; /* t1 = x0y0 + t1 + x1y1 */ - - /* Algorithm succeeded set the return code to MP_OKAY */ - err = MP_OKAY; - -X1Y1:mp_clear (&x1y1); -X0Y0:mp_clear (&x0y0); -T1:mp_clear (&t1); -Y1:mp_clear (&y1); -Y0:mp_clear (&y0); -X1:mp_clear (&x1); -X0:mp_clear (&x0); -ERR: - return err; + mp_int x0, x1, y0, y1, t1, x0y0, x1y1; + int B, err; + + /* default the return code to an error */ + err = MP_MEM; + + /* min # of digits */ + B = MIN(a->used, b->used); + + /* now divide in two */ + B = B >> 1; + + /* init copy all the temps */ + if (mp_init_size(&x0, B) != MP_OKAY) + goto LBL_ERR; + if (mp_init_size(&x1, a->used - B) != MP_OKAY) + goto X0; + if (mp_init_size(&y0, B) != MP_OKAY) + goto X1; + if (mp_init_size(&y1, b->used - B) != MP_OKAY) + goto Y0; + + /* init temps */ + if (mp_init_size(&t1, B * 2) != MP_OKAY) + goto Y1; + if (mp_init_size(&x0y0, B * 2) != MP_OKAY) + goto T1; + if (mp_init_size(&x1y1, B * 2) != MP_OKAY) + goto X0Y0; + + /* now shift the digits */ + x0.used = y0.used = B; + x1.used = a->used - B; + y1.used = b->used - B; + + { + int x; + mp_digit *tmpa, *tmpb, *tmpx, *tmpy; + + /* we copy the digits directly instead of using higher level functions + * since we also need to shift the digits + */ + tmpa = a->dp; + tmpb = b->dp; + + tmpx = x0.dp; + tmpy = y0.dp; + for (x = 0; x < B; x++) { + *tmpx++ = *tmpa++; + *tmpy++ = *tmpb++; + } + + tmpx = x1.dp; + for (x = B; x < a->used; x++) { + *tmpx++ = *tmpa++; + } + + tmpy = y1.dp; + for (x = B; x < b->used; x++) { + *tmpy++ = *tmpb++; + } + } + + /* only need to clamp the lower words since by definition the + * upper words x1/y1 must have a known number of digits + */ + mp_clamp(&x0); + mp_clamp(&y0); + + /* now calc the products x0y0 and x1y1 */ + /* after this x0 is no longer required, free temp [x0==t2]! */ + if (mp_mul(&x0, &y0, &x0y0) != MP_OKAY) + goto X1Y1; /* x0y0 = x0*y0 */ + if (mp_mul(&x1, &y1, &x1y1) != MP_OKAY) + goto X1Y1; /* x1y1 = x1*y1 */ + + /* now calc x1+x0 and y1+y0 */ + if (s_mp_add(&x1, &x0, &t1) != MP_OKAY) + goto X1Y1; /* t1 = x1 - x0 */ + if (s_mp_add(&y1, &y0, &x0) != MP_OKAY) + goto X1Y1; /* t2 = y1 - y0 */ + if (mp_mul(&t1, &x0, &t1) != MP_OKAY) + goto X1Y1; /* t1 = (x1 + x0) * (y1 + y0) */ + + /* add x0y0 */ + if (mp_add(&x0y0, &x1y1, &x0) != MP_OKAY) + goto X1Y1; /* t2 = x0y0 + x1y1 */ + if (s_mp_sub(&t1, &x0, &t1) != MP_OKAY) + goto X1Y1; /* t1 = (x1+x0)*(y1+y0) - (x1y1 + x0y0) */ + + /* shift by B */ + if (mp_lshd(&t1, B) != MP_OKAY) + goto X1Y1; /* t1 = (x0y0 + x1y1 - (x1-x0)*(y1-y0))<<B */ + if (mp_lshd(&x1y1, B * 2) != MP_OKAY) + goto X1Y1; /* x1y1 = x1y1 << 2*B */ + + if (mp_add(&x0y0, &t1, &t1) != MP_OKAY) + goto X1Y1; /* t1 = x0y0 + t1 */ + if (mp_add(&t1, &x1y1, c) != MP_OKAY) + goto X1Y1; /* t1 = x0y0 + t1 + x1y1 */ + + /* Algorithm succeeded set the return code to MP_OKAY */ + err = MP_OKAY; + +X1Y1: + mp_clear(&x1y1); +X0Y0: + mp_clear(&x0y0); +T1: + mp_clear(&t1); +Y1: + mp_clear(&y1); +Y0: + mp_clear(&y0); +X1: + mp_clear(&x1); +X0: + mp_clear(&x0); +LBL_ERR: + return err; } #endif -/* ref: $Format:%D$ */ -/* git commit: $Format:%H$ */ -/* commit time: $Format:%ai$ */ +/* ref: HEAD -> master, tag: v1.1.0 */ +/* git commit: 08549ad6bc8b0cede0b357a9c341c5c6473a9c55 */ +/* commit time: 2019-01-28 20:32:32 +0100 */ |