diff options
Diffstat (limited to 'libtommath/bn_s_mp_toom_mul.c')
| -rw-r--r-- | libtommath/bn_s_mp_toom_mul.c | 215 |
1 files changed, 215 insertions, 0 deletions
diff --git a/libtommath/bn_s_mp_toom_mul.c b/libtommath/bn_s_mp_toom_mul.c new file mode 100644 index 0000000..86901b0 --- /dev/null +++ b/libtommath/bn_s_mp_toom_mul.c @@ -0,0 +1,215 @@ +#include "tommath_private.h" +#ifdef BN_S_MP_TOOM_MUL_C +/* LibTomMath, multiple-precision integer library -- Tom St Denis */ +/* SPDX-License-Identifier: Unlicense */ + +/* multiplication using the Toom-Cook 3-way algorithm + * + * Much more complicated than Karatsuba but has a lower + * asymptotic running time of O(N**1.464). This algorithm is + * only particularly useful on VERY large inputs + * (we're talking 1000s of digits here...). +*/ + +/* + This file contains code from J. Arndt's book "Matters Computational" + and the accompanying FXT-library with permission of the author. +*/ + +/* + Setup from + + Chung, Jaewook, and M. Anwar Hasan. "Asymmetric squaring formulae." + 18th IEEE Symposium on Computer Arithmetic (ARITH'07). IEEE, 2007. + + The interpolation from above needed one temporary variable more + than the interpolation here: + + Bodrato, Marco, and Alberto Zanoni. "What about Toom-Cook matrices optimality." + Centro Vito Volterra Universita di Roma Tor Vergata (2006) +*/ + +mp_err s_mp_toom_mul(const mp_int *a, const mp_int *b, mp_int *c) +{ + mp_int S1, S2, T1, a0, a1, a2, b0, b1, b2; + int B, count; + mp_err err; + + /* init temps */ + if ((err = mp_init_multi(&S1, &S2, &T1, NULL)) != MP_OKAY) { + return err; + } + + /* B */ + B = MP_MIN(a->used, b->used) / 3; + + /** a = a2 * x^2 + a1 * x + a0; */ + if ((err = mp_init_size(&a0, B)) != MP_OKAY) goto LBL_ERRa0; + + for (count = 0; count < B; count++) { + a0.dp[count] = a->dp[count]; + a0.used++; + } + mp_clamp(&a0); + if ((err = mp_init_size(&a1, B)) != MP_OKAY) goto LBL_ERRa1; + for (; count < (2 * B); count++) { + a1.dp[count - B] = a->dp[count]; + a1.used++; + } + mp_clamp(&a1); + if ((err = mp_init_size(&a2, B + (a->used - (3 * B)))) != MP_OKAY) goto LBL_ERRa2; + for (; count < a->used; count++) { + a2.dp[count - (2 * B)] = a->dp[count]; + a2.used++; + } + mp_clamp(&a2); + + /** b = b2 * x^2 + b1 * x + b0; */ + if ((err = mp_init_size(&b0, B)) != MP_OKAY) goto LBL_ERRb0; + for (count = 0; count < B; count++) { + b0.dp[count] = b->dp[count]; + b0.used++; + } + mp_clamp(&b0); + if ((err = mp_init_size(&b1, B)) != MP_OKAY) goto LBL_ERRb1; + for (; count < (2 * B); count++) { + b1.dp[count - B] = b->dp[count]; + b1.used++; + } + mp_clamp(&b1); + if ((err = mp_init_size(&b2, B + (b->used - (3 * B)))) != MP_OKAY) goto LBL_ERRb2; + for (; count < b->used; count++) { + b2.dp[count - (2 * B)] = b->dp[count]; + b2.used++; + } + mp_clamp(&b2); + + /** \\ S1 = (a2+a1+a0) * (b2+b1+b0); */ + /** T1 = a2 + a1; */ + if ((err = mp_add(&a2, &a1, &T1)) != MP_OKAY) goto LBL_ERR; + + /** S2 = T1 + a0; */ + if ((err = mp_add(&T1, &a0, &S2)) != MP_OKAY) goto LBL_ERR; + + /** c = b2 + b1; */ + if ((err = mp_add(&b2, &b1, c)) != MP_OKAY) goto LBL_ERR; + + /** S1 = c + b0; */ + if ((err = mp_add(c, &b0, &S1)) != MP_OKAY) goto LBL_ERR; + + /** S1 = S1 * S2; */ + if ((err = mp_mul(&S1, &S2, &S1)) != MP_OKAY) goto LBL_ERR; + + /** \\S2 = (4*a2+2*a1+a0) * (4*b2+2*b1+b0); */ + /** T1 = T1 + a2; */ + if ((err = mp_add(&T1, &a2, &T1)) != MP_OKAY) goto LBL_ERR; + + /** T1 = T1 << 1; */ + if ((err = mp_mul_2(&T1, &T1)) != MP_OKAY) goto LBL_ERR; + + /** T1 = T1 + a0; */ + if ((err = mp_add(&T1, &a0, &T1)) != MP_OKAY) goto LBL_ERR; + + /** c = c + b2; */ + if ((err = mp_add(c, &b2, c)) != MP_OKAY) goto LBL_ERR; + + /** c = c << 1; */ + if ((err = mp_mul_2(c, c)) != MP_OKAY) goto LBL_ERR; + + /** c = c + b0; */ + if ((err = mp_add(c, &b0, c)) != MP_OKAY) goto LBL_ERR; + + /** S2 = T1 * c; */ + if ((err = mp_mul(&T1, c, &S2)) != MP_OKAY) goto LBL_ERR; + + /** \\S3 = (a2-a1+a0) * (b2-b1+b0); */ + /** a1 = a2 - a1; */ + if ((err = mp_sub(&a2, &a1, &a1)) != MP_OKAY) goto LBL_ERR; + + /** a1 = a1 + a0; */ + if ((err = mp_add(&a1, &a0, &a1)) != MP_OKAY) goto LBL_ERR; + + /** b1 = b2 - b1; */ + if ((err = mp_sub(&b2, &b1, &b1)) != MP_OKAY) goto LBL_ERR; + + /** b1 = b1 + b0; */ + if ((err = mp_add(&b1, &b0, &b1)) != MP_OKAY) goto LBL_ERR; + + /** a1 = a1 * b1; */ + if ((err = mp_mul(&a1, &b1, &a1)) != MP_OKAY) goto LBL_ERR; + + /** b1 = a2 * b2; */ + if ((err = mp_mul(&a2, &b2, &b1)) != MP_OKAY) goto LBL_ERR; + + /** \\S2 = (S2 - S3)/3; */ + /** S2 = S2 - a1; */ + if ((err = mp_sub(&S2, &a1, &S2)) != MP_OKAY) goto LBL_ERR; + + /** S2 = S2 / 3; \\ this is an exact division */ + if ((err = mp_div_3(&S2, &S2, NULL)) != MP_OKAY) goto LBL_ERR; + + /** a1 = S1 - a1; */ + if ((err = mp_sub(&S1, &a1, &a1)) != MP_OKAY) goto LBL_ERR; + + /** a1 = a1 >> 1; */ + if ((err = mp_div_2(&a1, &a1)) != MP_OKAY) goto LBL_ERR; + + /** a0 = a0 * b0; */ + if ((err = mp_mul(&a0, &b0, &a0)) != MP_OKAY) goto LBL_ERR; + + /** S1 = S1 - a0; */ + if ((err = mp_sub(&S1, &a0, &S1)) != MP_OKAY) goto LBL_ERR; + + /** S2 = S2 - S1; */ + if ((err = mp_sub(&S2, &S1, &S2)) != MP_OKAY) goto LBL_ERR; + + /** S2 = S2 >> 1; */ + if ((err = mp_div_2(&S2, &S2)) != MP_OKAY) goto LBL_ERR; + + /** S1 = S1 - a1; */ + if ((err = mp_sub(&S1, &a1, &S1)) != MP_OKAY) goto LBL_ERR; + + /** S1 = S1 - b1; */ + if ((err = mp_sub(&S1, &b1, &S1)) != MP_OKAY) goto LBL_ERR; + + /** T1 = b1 << 1; */ + if ((err = mp_mul_2(&b1, &T1)) != MP_OKAY) goto LBL_ERR; + + /** S2 = S2 - T1; */ + if ((err = mp_sub(&S2, &T1, &S2)) != MP_OKAY) goto LBL_ERR; + + /** a1 = a1 - S2; */ + if ((err = mp_sub(&a1, &S2, &a1)) != MP_OKAY) goto LBL_ERR; + + + /** P = b1*x^4+ S2*x^3+ S1*x^2+ a1*x + a0; */ + if ((err = mp_lshd(&b1, 4 * B)) != MP_OKAY) goto LBL_ERR; + if ((err = mp_lshd(&S2, 3 * B)) != MP_OKAY) goto LBL_ERR; + if ((err = mp_add(&b1, &S2, &b1)) != MP_OKAY) goto LBL_ERR; + if ((err = mp_lshd(&S1, 2 * B)) != MP_OKAY) goto LBL_ERR; + if ((err = mp_add(&b1, &S1, &b1)) != MP_OKAY) goto LBL_ERR; + if ((err = mp_lshd(&a1, 1 * B)) != MP_OKAY) goto LBL_ERR; + if ((err = mp_add(&b1, &a1, &b1)) != MP_OKAY) goto LBL_ERR; + if ((err = mp_add(&b1, &a0, c)) != MP_OKAY) goto LBL_ERR; + + /** a * b - P */ + + +LBL_ERR: + mp_clear(&b2); +LBL_ERRb2: + mp_clear(&b1); +LBL_ERRb1: + mp_clear(&b0); +LBL_ERRb0: + mp_clear(&a2); +LBL_ERRa2: + mp_clear(&a1); +LBL_ERRa1: + mp_clear(&a0); +LBL_ERRa0: + mp_clear_multi(&S1, &S2, &T1, NULL); + return err; +} + +#endif |