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/*
Copyright (C) 2021 Daniel Schultz
This file is part of FLINT.
FLINT is free software: you can redistribute it and/or modify it under
the terms of the GNU Lesser General Public License (LGPL) as published
by the Free Software Foundation; either version 3 of the License, or
(at your option) any later version. See <https://www.gnu.org/licenses/>.
*/
#include "longlong.h"
#include "mpoly.h"
#include "fmpz_mod_mpoly.h"
/*
sort terms in [left, right) by exponent
assuming that bits in position >= pos are already sorted
and assuming exponent vectors fit into one word
and assuming that all bit positions that need to be sorted are in totalmask
*/
void _fmpz_mod_mpoly_radix_sort1(
fmpz * Acoeffs,
ulong * Aexps,
slong left, slong right,
flint_bitcnt_t pos,
ulong cmpmask,
ulong totalmask)
{
ulong mask, cmp;
slong mid, cur;
while (pos > 0)
{
pos--;
FLINT_ASSERT(left <= right);
FLINT_ASSERT(pos < FLINT_BITS);
mask = UWORD(1) << pos;
cmp = cmpmask & mask;
/* insertion base case */
if (right - left < 10)
{
slong i, j;
for (i = left + 1; i < right; i++)
{
for (j = i; j > left && mpoly_monomial_gt1(Aexps[j],
Aexps[j - 1], cmpmask); j--)
{
fmpz_swap(Acoeffs + j, Acoeffs + j - 1);
FLINT_SWAP(ulong, Aexps[j], Aexps[j - 1]);
}
}
return;
}
/* return if there is no information to sort on this bit */
if ((totalmask & mask) == 0)
continue;
/* find first 'zero' */
mid = left;
while (mid < right && (Aexps[mid] & mask) != cmp)
mid++;
/* make sure [left,mid) doesn't match cmpmask in position pos 'one'
[mid,right) does match cmpmask in position pos 'zero' */
cur = mid;
while (++cur < right)
{
if ((Aexps[cur] & mask) != cmp)
{
fmpz_swap(Acoeffs + cur, Acoeffs + mid);
FLINT_SWAP(ulong, Aexps[cur], Aexps[mid]);
mid++;
}
}
if (mid - left < right - mid)
{
_fmpz_mod_mpoly_radix_sort1(Acoeffs, Aexps, left, mid,
pos, cmpmask, totalmask);
left = mid;
}
else
{
_fmpz_mod_mpoly_radix_sort1(Acoeffs, Aexps, mid, right,
pos, cmpmask, totalmask);
right = mid;
}
}
}
/*
sort terms in [left, right) by exponent
assuming that bits in position >= pos are already sorted
*/
void _fmpz_mod_mpoly_radix_sort(
fmpz * Acoeffs,
ulong * Aexps,
slong left, slong right,
flint_bitcnt_t pos,
slong N,
ulong * cmpmask)
{
ulong off, bit, mask, cmp;
slong mid, check;
while (pos > 0)
{
pos--;
FLINT_ASSERT(left <= right);
FLINT_ASSERT(pos < N*FLINT_BITS);
off = pos/FLINT_BITS;
bit = pos%FLINT_BITS;
mask = UWORD(1) << bit;
cmp = cmpmask[off] & mask;
/* insertion base case */
if (right - left < 20)
{
slong i, j;
for (i = left + 1; i < right; i++)
{
for (j = i; j > left && mpoly_monomial_gt(Aexps + N*j,
Aexps + N*(j - 1), N, cmpmask); j--)
{
fmpz_swap(Acoeffs + j, Acoeffs + j - 1);
mpoly_monomial_swap(Aexps + N*j, Aexps + N*(j - 1), N);
}
}
return;
}
/* find first 'zero' */
mid = left;
while (mid < right && ((Aexps+N*mid)[off] & mask) != cmp)
mid++;
/* make sure [left,mid) doesn't match cmpmask in position pos 'one'
[mid,right) does match cmpmask in position pos 'zero' */
check = mid;
while (++check < right)
{
if (((Aexps + N*check)[off] & mask) != cmp)
{
fmpz_swap(Acoeffs + check, Acoeffs + mid);
mpoly_monomial_swap(Aexps + N*check, Aexps + N*mid, N);
mid++;
}
}
FLINT_ASSERT(left <= mid && mid <= right);
if (mid - left < right - mid)
{
_fmpz_mod_mpoly_radix_sort(Acoeffs, Aexps, left, mid,
pos, N, cmpmask);
left = mid;
}
else
{
_fmpz_mod_mpoly_radix_sort(Acoeffs, Aexps, mid, right,
pos, N, cmpmask);
right = mid;
}
}
}
/*
sort the terms in A by exponent
assuming that the exponents are valid (other than being in order)
*/
void fmpz_mod_mpoly_sort_terms(fmpz_mod_mpoly_t A, const fmpz_mod_mpoly_ctx_t ctx)
{
slong i, N;
flint_bitcnt_t pos;
fmpz * Acoeffs = A->coeffs;
ulong * Aexps = A->exps;
ulong himask, * ptempexp;
TMP_INIT;
TMP_START;
N = mpoly_words_per_exp(A->bits, ctx->minfo);
ptempexp = (ulong *) TMP_ALLOC(N*sizeof(ulong));
mpoly_get_cmpmask(ptempexp, N, A->bits, ctx->minfo);
himask = 0;
for (i = 0; i < A->length; i++)
himask |= (Aexps + N*i)[N - 1];
pos = FLINT_BIT_COUNT(himask);
if (N == 1)
_fmpz_mod_mpoly_radix_sort1(Acoeffs, Aexps, 0, A->length,
pos, ptempexp[0], himask);
else
_fmpz_mod_mpoly_radix_sort(Acoeffs, Aexps, 0, A->length,
(N - 1)*FLINT_BITS + pos, N, ptempexp);
TMP_END;
}