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DOC: improve inline comments in pb_inverse_poly_q()

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These should also match the actual mathematical computations.
This commit is contained in:
hasufell 2014-04-29 14:27:15 +02:00
parent 12b8b08700
commit 777a086c53
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GPG Key ID: 220CD1C5BDEED020
1 changed files with 9 additions and 2 deletions
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11
src/poly.c
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@ -136,7 +136,7 @@ pb_poly *build_polynom(int const * const c,
if (sign == true) if (sign == true)
mp_neg(&(new_poly->terms[i]), &(new_poly->terms[i])); mp_neg(&(new_poly->terms[i]), &(new_poly->terms[i]));
} }
} else { /* fill with zeros */ } else { /* fill with 0 */
for (unsigned int i = 0; i < len; i++) for (unsigned int i = 0; i < len; i++)
MP_SET(&(new_poly->terms[i]), 0); MP_SET(&(new_poly->terms[i]), 0);
} }
@ -311,7 +311,6 @@ static void pb_mod2_to_modq(pb_poly * const a,
pb_tmp2 = build_polynom(NULL, ctx->N, ctx); pb_tmp2 = build_polynom(NULL, ctx->N, ctx);
MP_SET_INT(&(pb_tmp2->terms[0]), 2); MP_SET_INT(&(pb_tmp2->terms[0]), 2);
/* mod after sub or before? */
pb_starmultiply(a, Fq, pb_tmp, ctx, v); pb_starmultiply(a, Fq, pb_tmp, ctx, v);
PB_SUB(pb_tmp2, pb_tmp, pb_tmp); PB_SUB(pb_tmp2, pb_tmp, pb_tmp);
PB_MOD(pb_tmp, &tmp_v, pb_tmp, ctx->N); PB_MOD(pb_tmp, &tmp_v, pb_tmp, ctx->N);
@ -338,15 +337,19 @@ bool pb_inverse_poly_q(pb_poly * const a,
j = 0; j = 0;
pb_poly *a_tmp, *b, *c, *f, *g; pb_poly *a_tmp, *b, *c, *f, *g;
/* general initialization of temp variables */
b = build_polynom(NULL, ctx->N + 1, ctx); b = build_polynom(NULL, ctx->N + 1, ctx);
MP_SET(&(b->terms[0]), 1); MP_SET(&(b->terms[0]), 1);
c = build_polynom(NULL, ctx->N + 1, ctx); c = build_polynom(NULL, ctx->N + 1, ctx);
f = build_polynom(NULL, ctx->N + 1, ctx); f = build_polynom(NULL, ctx->N + 1, ctx);
PB_COPY(a, f); PB_COPY(a, f);
/* set g(x) = x^N − 1 */
g = build_polynom(NULL, ctx->N + 1, ctx); g = build_polynom(NULL, ctx->N + 1, ctx);
MP_SET(&(g->terms[0]), 1); MP_SET(&(g->terms[0]), 1);
mp_neg(&(g->terms[0]), &(g->terms[0])); mp_neg(&(g->terms[0]), &(g->terms[0]));
MP_SET(&(g->terms[ctx->N]), 1); MP_SET(&(g->terms[ctx->N]), 1);
/* avoid side effects */ /* avoid side effects */
a_tmp = build_polynom(NULL, ctx->N, ctx); a_tmp = build_polynom(NULL, ctx->N, ctx);
PB_COPY(a, a_tmp); PB_COPY(a, a_tmp);
@ -355,7 +358,9 @@ bool pb_inverse_poly_q(pb_poly * const a,
while (1) { while (1) {
while (mp_cmp_d(&(f->terms[0]), 0) == MP_EQ) { while (mp_cmp_d(&(f->terms[0]), 0) == MP_EQ) {
for (unsigned int i = 1; i <= ctx->N; i++) { for (unsigned int i = 1; i <= ctx->N; i++) {
/* f(x) = f(x) / x */
MP_COPY(&(f->terms[i]), &(f->terms[i - 1])); MP_COPY(&(f->terms[i]), &(f->terms[i - 1]));
/* c(x) = c(x) * x */
MP_COPY(&(c->terms[ctx->N - i]), &(c->terms[ctx->N + 1 - i])); MP_COPY(&(c->terms[ctx->N - i]), &(c->terms[ctx->N + 1 - i]));
} }
MP_SET(&(f->terms[ctx->N]), 0); MP_SET(&(f->terms[ctx->N]), 0);
@ -378,6 +383,7 @@ bool pb_inverse_poly_q(pb_poly * const a,
OUT_OF_LOOP: OUT_OF_LOOP:
k = k % ctx->N; k = k % ctx->N;
/* Fq(x) = x^(N-k) * b(x) */
for (int i = ctx->N - 1; i >= 0; i--) { for (int i = ctx->N - 1; i >= 0; i--) {
j = i - k; j = i - k;
if (j < 0) if (j < 0)
@ -387,6 +393,7 @@ OUT_OF_LOOP:
pb_mod2_to_modq(a_tmp, Fq, ctx); pb_mod2_to_modq(a_tmp, Fq, ctx);
/* pull into positive space */
for (int i = ctx->N - 1; i >= 0; i--) for (int i = ctx->N - 1; i >= 0; i--)
if (mp_cmp_d(&(Fq->terms[i]), 0) == MP_LT) { if (mp_cmp_d(&(Fq->terms[i]), 0) == MP_LT) {
mp_int mp_tmp; mp_int mp_tmp;