X-Git-Url: https://git.distorted.org.uk/u/mdw/catacomb/blobdiff_plain/ba6e6b64033b1f9de49feccb5c9cd438354481f7..0f00dc4c8eb47e67bc0f148c2dd109f73a451e0a:/gfreduce.c

diff --git a/gfreduce.c b/gfreduce.c
deleted file mode 100644
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--- a/gfreduce.c
+++ /dev/null
@@ -1,652 +0,0 @@
-/* -*-c-*-
- *
- * $Id$
- *
- * Efficient reduction modulo sparse binary polynomials
- *
- * (c) 2004 Straylight/Edgeware
- */
-
-/*----- Licensing notice --------------------------------------------------*
- *
- * This file is part of Catacomb.
- *
- * Catacomb is free software; you can redistribute it and/or modify
- * it under the terms of the GNU Library General Public License as
- * published by the Free Software Foundation; either version 2 of the
- * License, or (at your option) any later version.
- *
- * Catacomb is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU Library General Public License for more details.
- *
- * You should have received a copy of the GNU Library General Public
- * License along with Catacomb; if not, write to the Free
- * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
- * MA 02111-1307, USA.
- */
-
-/*----- Header files ------------------------------------------------------*/
-
-#include <mLib/alloc.h>
-#include <mLib/darray.h>
-#include <mLib/macros.h>
-
-#include "gf.h"
-#include "gfreduce.h"
-#include "gfreduce-exp.h"
-#include "fibrand.h"
-#include "mprand.h"
-
-/*----- Data structures ---------------------------------------------------*/
-
-DA_DECL(instr_v, gfreduce_instr);
-
-/*----- Main code ---------------------------------------------------------*/
-
-/* --- What's going on here? --- *
- *
- * Let's face it, @gfx_div@ sucks.  It works (I hope), but it's not in any
- * sense fast.  Here, we do efficient reduction modulo sparse polynomials.
- *
- * Suppose we have a polynomial @X@ we're trying to reduce mod @P@.  If we
- * take the topmost nonzero word of @X@, call it @w@, then we can eliminate
- * it by subtracting off @w P x^{k}@ for an appropriate value of @k@.  The
- * trick is in observing that if @P@ is sparse we can do this multiplication
- * and subtraction efficiently, just by XORing appropriate shifts of @w@ into
- * @X@.
- *
- * The first tricky bit is in working out when to stop.  I'll use eight-bit
- * words to demonstrate what I'm talking about.
- *
- *  xxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx
- *		    001ppppp pppppppp pppppppp pppppppp
- *		      |<rp>|
- *		      |<------------ bp ------------->|
- *		    |<------------ nw --------------->|
- *
- * The trick of taking whole words off of @X@ stops working when there are
- * only @nw@ words left.  Then we have to mask off the bottom bits of @w@
- * before continuing.
- */
-
-/* --- @gfreduce_create@ --- *
- *
- * Arguments:	@gfreduce *r@ = structure to fill in
- *		@mp *x@ = a (hopefully sparse) polynomial
- *
- * Returns:	---
- *
- * Use:		Initializes a context structure for reduction.
- */
-
-void gfreduce_create(gfreduce *r, mp *p)
-{
-  instr_v iv = DA_INIT;
-  unsigned long d;
-  unsigned dw;
-  mpscan sc;
-  unsigned long i;
-  gfreduce_instr *ip;
-  unsigned f = 0;
-  size_t w, ww, wi, wl, ll, bb;
-
-  /* --- Sort out the easy stuff --- */
-
-  d = mp_bits(p); assert(d); d--;
-  r->lim = d/MPW_BITS;
-  dw = d%MPW_BITS;
-  if (!dw)
-    r->mask = 0;
-  else {
-    r->mask = MPW(((mpw)-1) << dw);
-    r->lim++;
-  }
-  r->p = mp_copy(p);
-
-  /* --- Stash a new instruction --- */
-
-#define INSTR(op_, arg_) do {						\
-  DA_ENSURE(&iv, 1);							\
-  DA(&iv)[DA_LEN(&iv)].op = (op_);					\
-  DA(&iv)[DA_LEN(&iv)].arg = (arg_);					\
-  DA_EXTEND(&iv, 1);							\
-} while (0)
-
-#define f_lsr 1u
-
-  w = (d + MPW_BITS - 1)/MPW_BITS;
-  INSTR(GFRI_LOAD, w);
-  wi = DA_LEN(&iv);
-  f = 0;
-  ll = 0;
-  bb = MPW_BITS - dw;
-  for (i = 0, mp_scan(&sc, p); mp_step(&sc) && i < d; i++) {
-    if (!mp_bit(&sc))
-      continue;
-    ww = (d - i + MPW_BITS - 1)/MPW_BITS;
-    if (ww != w) {
-      wl = DA_LEN(&iv);
-      INSTR(GFRI_STORE, w);
-      if (!ll)
-	ll = DA_LEN(&iv);
-      if (!(f & f_lsr))
-	INSTR(GFRI_LOAD, ww);
-      else {
-	INSTR(GFRI_LOAD, w - 1);
-	for (; wi < wl; wi++) {
-	  ip = &DA(&iv)[wi];
-	  assert(ip->op == GFRI_LSL);
-	  if (ip->arg)
-	    INSTR(GFRI_LSR, MPW_BITS - ip->arg);
-	}
-	if (w - 1 != ww) {
-	  INSTR(GFRI_STORE, w - 1);
-	  INSTR(GFRI_LOAD, ww);
-	}
-	f &= ~f_lsr;
-      }
-      w = ww;
-      wi = DA_LEN(&iv);
-    }
-    INSTR(GFRI_LSL, (bb + i)%MPW_BITS);
-    if ((bb + i)%MPW_BITS)
-      f |= f_lsr;
-  }
-  wl = DA_LEN(&iv);
-  INSTR(GFRI_STORE, w);
-  if (!ll)
-    ll = DA_LEN(&iv);
-  if (f & f_lsr) {
-    INSTR(GFRI_LOAD, w - 1);
-    for (; wi < wl; wi++) {
-      ip = &DA(&iv)[wi];
-      assert(ip->op == GFRI_LSL);
-      if (ip->arg)
-	INSTR(GFRI_LSR, MPW_BITS - ip->arg);
-    }
-    INSTR(GFRI_STORE, w - 1);
-  }
-
-#undef INSTR
-
-  r->in = DA_LEN(&iv);
-  r->iv = xmalloc(r->in * sizeof(gfreduce_instr));
-  r->liv = r->iv + ll;
-  memcpy(r->iv, DA(&iv), r->in * sizeof(gfreduce_instr));
-  DA_DESTROY(&iv);
-}
-
-/* --- @gfreduce_destroy@ --- *
- *
- * Arguments:	@gfreduce *r@ = structure to free
- *
- * Returns:	---
- *
- * Use:		Reclaims the resources from a reduction context.
- */
-
-void gfreduce_destroy(gfreduce *r)
-{
-  mp_drop(r->p);
-  xfree(r->iv);
-}
-
-/* --- @gfreduce_dump@ --- *
- *
- * Arguments:	@gfreduce *r@ = structure to dump
- *		@FILE *fp@ = file to dump on
- *
- * Returns:	---
- *
- * Use:		Dumps a reduction context.
- */
-
-void gfreduce_dump(gfreduce *r, FILE *fp)
-{
-  size_t i;
-
-  fprintf(fp, "poly = "); mp_writefile(r->p, fp, 16);
-  fprintf(fp, "\n  lim = %lu; mask = %lx\n",
-	  (unsigned long)r->lim, (unsigned long)r->mask);
-  for (i = 0; i < r->in; i++) {
-    static const char *opname[] = { "load", "lsl", "lsr", "store" };
-    assert(r->iv[i].op < N(opname));
-    fprintf(fp, "  %s %lu\n",
-	    opname[r->iv[i].op],
-	    (unsigned long)r->iv[i].arg);
-  }
-}
-
-/* --- @gfreduce_do@ --- *
- *
- * Arguments:	@gfreduce *r@ = reduction context
- *		@mp *d@ = destination
- *		@mp *x@ = source
- *
- * Returns:	Destination, @x@ reduced modulo the reduction poly.
- */
-
-static void run(const gfreduce_instr *i, const gfreduce_instr *il,
-		mpw *v, mpw z)
-{
-  mpw w = 0;
-
-  for (; i < il; i++) {
-    switch (i->op) {
-      case GFRI_LOAD: w = *(v - i->arg); break;
-      case GFRI_LSL: w ^= z << i->arg; break;
-      case GFRI_LSR: w ^= z >> i->arg; break;
-      case GFRI_STORE: *(v - i->arg) = MPW(w); break;
-      default: abort();
-    }
-  }
-}
-
-mp *gfreduce_do(gfreduce *r, mp *d, mp *x)
-{
-  mpw *v, *vl;
-  const gfreduce_instr *il;
-  mpw z;
-
-  /* --- Try to reuse the source's space --- */
-
-  MP_COPY(x);
-  if (d) MP_DROP(d);
-  MP_DEST(x, MP_LEN(x), x->f);
-
-  /* --- Do the reduction --- */
-
-  il = r->iv + r->in;
-  if (MP_LEN(x) >= r->lim) {
-    v = x->v + r->lim;
-    vl = x->vl;
-    while (vl-- > v) {
-      while (*vl) {
-	z = *vl;
-	*vl = 0;
-	run(r->iv, il, vl, z);
-      }
-    }
-    if (r->mask) {
-      while (*vl & r->mask) {
-	z = *vl & r->mask;
-	*vl &= ~r->mask;
-	run(r->iv, il, vl, z);
-      }
-    }
-  }
-
-  /* --- Done --- */
-
-  MP_SHRINK(x);
-  return (x);
-}
-
-/* --- @gfreduce_sqrt@ --- *
- *
- * Arguments:	@gfreduce *r@ = pointer to reduction context
- *		@mp *d@ = destination
- *		@mp *x@ = some polynomial
- *
- * Returns:	The square root of @x@ modulo @r->p@, or null.
- */
-
-mp *gfreduce_sqrt(gfreduce *r, mp *d, mp *x)
-{
-  mp *y = MP_COPY(x);
-  mp *z, *spare = MP_NEW;
-  unsigned long m = mp_bits(r->p) - 1;
-  unsigned long i;
-
-  for (i = 0; i < m - 1; i++) {
-    mp *t = gf_sqr(spare, y);
-    spare = y;
-    y = gfreduce_do(r, t, t);
-  }
-  z = gf_sqr(spare, y);
-  z = gfreduce_do(r, z, z);
-  if (!MP_EQ(x, z)) {
-    mp_drop(y);
-    y = 0;
-  }
-  mp_drop(z);
-  mp_drop(d);
-  return (y);
-}
-
-/* --- @gfreduce_trace@ --- *
- *
- * Arguments:	@gfreduce *r@ = pointer to reduction context
- *		@mp *x@ = some polynomial
- *
- * Returns:	The trace of @x@. (%$\Tr(x)=x + x^2 + \cdots + x^{2^{m-1}}$%
- *		if %$x \in \gf{2^m}$%).
- */
-
-int gfreduce_trace(gfreduce *r, mp *x)
-{
-  mp *y = MP_COPY(x);
-  mp *spare = MP_NEW;
-  unsigned long m = mp_bits(r->p) - 1;
-  unsigned long i;
-  int rc;
-
-  for (i = 0; i < m - 1; i++) {
-    mp *t = gf_sqr(spare, y);
-    spare = y;
-    y = gfreduce_do(r, t, t);
-    y = gf_add(y, y, x);
-  }
-  rc = !MP_ZEROP(y);
-  mp_drop(spare);
-  mp_drop(y);
-  return (rc);
-}
-
-/* --- @gfreduce_halftrace@ --- *
- *
- * Arguments:	@gfreduce *r@ = pointer to reduction context
- *		@mp *d@ = destination
- *		@mp *x@ = some polynomial
- *
- * Returns:	The half-trace of @x@.
- *		(%$\HfTr(x)= x + x^{2^2} + \cdots + x^{2^{m-1}}$%
- *		if %$x \in \gf{2^m}$% with %$m$% odd).
- */
-
-mp *gfreduce_halftrace(gfreduce *r, mp *d, mp *x)
-{
-  mp *y = MP_COPY(x);
-  mp *spare = MP_NEW;
-  unsigned long m = mp_bits(r->p) - 1;
-  unsigned long i;
-
-  mp_drop(d);
-  for (i = 0; i < m - 1; i += 2) {
-    mp *t = gf_sqr(spare, y);
-    spare = y;
-    y = gfreduce_do(r, t, t);
-    t = gf_sqr(spare, y);
-    spare = y;
-    y = gfreduce_do(r, t, t);
-    y = gf_add(y, y, x);
-  }
-  mp_drop(spare);
-  return (y);
-}
-
-/* --- @gfreduce_quadsolve@ --- *
- *
- * Arguments:	@gfreduce *r@ = pointer to reduction context
- *		@mp *d@ = destination
- *		@mp *x@ = some polynomial
- *
- * Returns:	A polynomial @y@ such that %$y^2 + y = x$%, or null.
- */
-
-mp *gfreduce_quadsolve(gfreduce *r, mp *d, mp *x)
-{
-  unsigned long m = mp_bits(r->p) - 1;
-  mp *t;
-
-  MP_COPY(x);
-  if (m & 1)
-    d = gfreduce_halftrace(r, d, x);
-  else {
-    mp *z, *w, *rho = MP_NEW;
-    mp *spare = MP_NEW;
-    grand *fr = fibrand_create(0);
-    unsigned long i;
-
-    for (;;) {
-      rho = mprand(rho, m, fr, 0);
-      z = MP_ZERO;
-      w = MP_COPY(rho);
-      for (i = 0; i < m - 1; i++) {
-	t = gf_sqr(spare, z); spare = z; z = gfreduce_do(r, t, t);
-	t = gf_sqr(spare, w); spare = w; w = gfreduce_do(r, t, t);
-	t = gf_mul(spare, w, x); t = gfreduce_do(r, t, t); spare = t;
-	z = gf_add(z, z, t);
-	w = gf_add(w, w, rho);
-      }
-      if (!MP_ZEROP(w))
-	break;
-      MP_DROP(z);
-      MP_DROP(w);
-    }
-    if (d) MP_DROP(d);
-    MP_DROP(w);
-    MP_DROP(spare);
-    MP_DROP(rho);
-    fr->ops->destroy(fr);
-    d = z;
-  }
-
-  t = gf_sqr(MP_NEW, d); t = gfreduce_do(r, t, t); t = gf_add(t, t, d);
-  if (!MP_EQ(t, x)) {
-    MP_DROP(d);
-    d = 0;
-  }
-  MP_DROP(t);
-  MP_DROP(x);
-  if (d) d->v[0] &= ~(mpw)1;
-  return (d);
-}
-
-/* --- @gfreduce_exp@ --- *
- *
- * Arguments:	@gfreduce *gr@ = pointer to reduction context
- *		@mp *d@ = fake destination
- *		@mp *a@ = base
- *		@mp *e@ = exponent
- *
- * Returns:	Result, %$a^e \bmod m$%.
- */
-
-mp *gfreduce_exp(gfreduce *gr, mp *d, mp *a, mp *e)
-{
-  mp *x = MP_ONE;
-  mp *spare = (e->f & MP_BURN) ? MP_NEWSEC : MP_NEW;
-
-  MP_SHRINK(e);
-  MP_COPY(a);
-  if (MP_ZEROP(e))
-    ;
-  else {
-    if (MP_NEGP(e))
-      a = gf_modinv(a, a, gr->p);
-    if (MP_LEN(e) < EXP_THRESH)
-      EXP_SIMPLE(x, a, e);
-    else
-      EXP_WINDOW(x, a, e);
-  }
-  mp_drop(d);
-  mp_drop(a);
-  mp_drop(spare);
-  return (x);
-}
-
-/*----- Test rig ----------------------------------------------------------*/
-
-#ifdef TEST_RIG
-
-#define MP(x) mp_readstring(MP_NEW, #x, 0, 0)
-
-static int vreduce(dstr *v)
-{
-  mp *d = *(mp **)v[0].buf;
-  mp *n = *(mp **)v[1].buf;
-  mp *r = *(mp **)v[2].buf;
-  mp *c;
-  int ok = 1;
-  gfreduce rr;
-
-  gfreduce_create(&rr, d);
-  c = gfreduce_do(&rr, MP_NEW, n);
-  if (!MP_EQ(c, r)) {
-    fprintf(stderr, "\n*** reduction failed\n*** ");
-    gfreduce_dump(&rr, stderr);
-    fprintf(stderr, "\n*** n = "); mp_writefile(n, stderr, 16);
-    fprintf(stderr, "\n*** r = "); mp_writefile(r, stderr, 16);
-    fprintf(stderr, "\n*** c = "); mp_writefile(c, stderr, 16);
-    fprintf(stderr, "\n");
-    ok = 0;
-  }
-  gfreduce_destroy(&rr);
-  mp_drop(n); mp_drop(d); mp_drop(r); mp_drop(c);
-  assert(mparena_count(MPARENA_GLOBAL) == 0);
-  return (ok);
-}
-
-static int vmodexp(dstr *v)
-{
-  mp *p = *(mp **)v[0].buf;
-  mp *g = *(mp **)v[1].buf;
-  mp *x = *(mp **)v[2].buf;
-  mp *r = *(mp **)v[3].buf;
-  mp *c;
-  int ok = 1;
-  gfreduce rr;
-
-  gfreduce_create(&rr, p);
-  c = gfreduce_exp(&rr, MP_NEW, g, x);
-  if (!MP_EQ(c, r)) {
-    fprintf(stderr, "\n*** modexp failed\n*** ");
-    fprintf(stderr, "\n*** p = "); mp_writefile(p, stderr, 16);
-    fprintf(stderr, "\n*** g = "); mp_writefile(g, stderr, 16);
-    fprintf(stderr, "\n*** x = "); mp_writefile(x, stderr, 16);
-    fprintf(stderr, "\n*** c = "); mp_writefile(c, stderr, 16);
-    fprintf(stderr, "\n*** r = "); mp_writefile(r, stderr, 16);
-    fprintf(stderr, "\n");
-    ok = 0;
-  }
-  gfreduce_destroy(&rr);
-  mp_drop(p); mp_drop(g); mp_drop(r); mp_drop(x); mp_drop(c);
-  assert(mparena_count(MPARENA_GLOBAL) == 0);
-  return (ok);
-}
-
-static int vsqrt(dstr *v)
-{
-  mp *p = *(mp **)v[0].buf;
-  mp *x = *(mp **)v[1].buf;
-  mp *r = *(mp **)v[2].buf;
-  mp *c;
-  int ok = 1;
-  gfreduce rr;
-
-  gfreduce_create(&rr, p);
-  c = gfreduce_sqrt(&rr, MP_NEW, x);
-  if (!MP_EQ(c, r)) {
-    fprintf(stderr, "\n*** sqrt failed\n*** ");
-    fprintf(stderr, "\n*** p = "); mp_writefile(p, stderr, 16);
-    fprintf(stderr, "\n*** x = "); mp_writefile(x, stderr, 16);
-    fprintf(stderr, "\n*** c = "); mp_writefile(c, stderr, 16);
-    fprintf(stderr, "\n*** r = "); mp_writefile(r, stderr, 16);
-    fprintf(stderr, "\n");
-    ok = 0;
-  }
-  gfreduce_destroy(&rr);
-  mp_drop(p); mp_drop(r); mp_drop(x); mp_drop(c);
-  assert(mparena_count(MPARENA_GLOBAL) == 0);
-  return (ok);
-}
-
-static int vtr(dstr *v)
-{
-  mp *p = *(mp **)v[0].buf;
-  mp *x = *(mp **)v[1].buf;
-  int r = *(int *)v[2].buf, c;
-  int ok = 1;
-  gfreduce rr;
-
-  gfreduce_create(&rr, p);
-  c = gfreduce_trace(&rr, x);
-  if (c != r) {
-    fprintf(stderr, "\n*** trace failed\n*** ");
-    fprintf(stderr, "\n*** p = "); mp_writefile(p, stderr, 16);
-    fprintf(stderr, "\n*** x = "); mp_writefile(x, stderr, 16);
-    fprintf(stderr, "\n*** c = %d", c);
-    fprintf(stderr, "\n*** r = %d", r);
-    fprintf(stderr, "\n");
-    ok = 0;
-  }
-  gfreduce_destroy(&rr);
-  mp_drop(p); mp_drop(x);
-  assert(mparena_count(MPARENA_GLOBAL) == 0);
-  return (ok);
-}
-
-static int vhftr(dstr *v)
-{
-  mp *p = *(mp **)v[0].buf;
-  mp *x = *(mp **)v[1].buf;
-  mp *r = *(mp **)v[2].buf;
-  mp *c;
-  int ok = 1;
-  gfreduce rr;
-
-  gfreduce_create(&rr, p);
-  c = gfreduce_halftrace(&rr, MP_NEW, x);
-  if (!MP_EQ(c, r)) {
-    fprintf(stderr, "\n*** halftrace failed\n*** ");
-    fprintf(stderr, "\n*** p = "); mp_writefile(p, stderr, 16);
-    fprintf(stderr, "\n*** x = "); mp_writefile(x, stderr, 16);
-    fprintf(stderr, "\n*** c = "); mp_writefile(c, stderr, 16);
-    fprintf(stderr, "\n*** r = "); mp_writefile(r, stderr, 16);
-    fprintf(stderr, "\n");
-    ok = 0;
-  }
-  gfreduce_destroy(&rr);
-  mp_drop(p); mp_drop(r); mp_drop(x); mp_drop(c);
-  assert(mparena_count(MPARENA_GLOBAL) == 0);
-  return (ok);
-}
-
-static int vquad(dstr *v)
-{
-  mp *p = *(mp **)v[0].buf;
-  mp *x = *(mp **)v[1].buf;
-  mp *r = *(mp **)v[2].buf;
-  mp *c;
-  int ok = 1;
-  gfreduce rr;
-
-  gfreduce_create(&rr, p);
-  c = gfreduce_quadsolve(&rr, MP_NEW, x);
-  if (!MP_EQ(c, r)) {
-    fprintf(stderr, "\n*** quadsolve failed\n*** ");
-    fprintf(stderr, "\n*** p = "); mp_writefile(p, stderr, 16);
-    fprintf(stderr, "\n*** x = "); mp_writefile(x, stderr, 16);
-    fprintf(stderr, "\n*** c = "); mp_writefile(c, stderr, 16);
-    fprintf(stderr, "\n*** r = "); mp_writefile(r, stderr, 16);
-    fprintf(stderr, "\n");
-    ok = 0;
-  }
-  gfreduce_destroy(&rr);
-  mp_drop(p); mp_drop(r); mp_drop(x); mp_drop(c);
-  assert(mparena_count(MPARENA_GLOBAL) == 0);
-  return (ok);
-}
-
-static test_chunk defs[] = {
-  { "reduce", vreduce, { &type_mp, &type_mp, &type_mp, 0 } },
-  { "modexp", vmodexp, { &type_mp, &type_mp, &type_mp, &type_mp, 0 } },
-  { "sqrt", vsqrt, { &type_mp, &type_mp, &type_mp, 0 } },
-  { "trace", vtr, { &type_mp, &type_mp, &type_int, 0 } },
-  { "halftrace", vhftr, { &type_mp, &type_mp, &type_mp, 0 } },
-  { "quadsolve", vquad, { &type_mp, &type_mp, &type_mp, 0 } },
-  { 0, 0, { 0 } }
-};
-
-int main(int argc, char *argv[])
-{
-  test_run(argc, argv, defs, SRCDIR"/tests/gfreduce");
-  return (0);
-}
-
-#endif
-
-/*----- That's all, folks -------------------------------------------------*/