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/*
Copyright (C) 2017 William Hart
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 "mpoly.h"
static int mpoly_monomial_exists1(slong * index, const ulong * poly_exps,
const ulong exp, slong len, ulong maskhi)
{
slong n = len;
slong i = 0;
if ((exp^maskhi) > (poly_exps[0]^maskhi)) /* greater than first term */
{
(*index) = 0;
return 0;
}
while (n > 1) /* do binary search */
{
slong half = n/2;
/* if in first half */
if ((exp^maskhi) > (poly_exps[i + half]^maskhi))
n = half;
else /* in second half */
{
n -= half;
i += half;
}
}
/* if equal to term at index i */
if (exp == poly_exps[i])
{
(*index) = i;
return 1;
} else /* less than term at index i, but doesn't exist */
{
(*index) = i + 1;
return 0;
}
}
int mpoly_monomial_exists(slong * index, const ulong * poly_exps,
const ulong * exp, slong len, slong N, const ulong * cmpmask)
{
slong n = len;
slong i = 0;
if (len == 0) /* no terms to search */
{
(*index) = 0;
return 0;
}
/* specialised version if exponent vectors are one word */
if (N == 1)
return mpoly_monomial_exists1(index, poly_exps, *exp, len, cmpmask[0]);
if (mpoly_monomial_gt(exp, poly_exps, N, cmpmask)) /* greater than first term */
{
(*index) = 0;
return 0;
}
while (n > 1) /* do binary search */
{
slong half = n/2;
/* if in first half */
if (mpoly_monomial_gt(exp, poly_exps + (i + half)*N, N, cmpmask))
n = half;
else /* in second half */
{
n -= half;
i += half;
}
}
/* if equal to term at index i */
if (mpoly_monomial_equal(exp, poly_exps + i*N, N))
{
(*index) = i;
return 1;
} else /* less than term at index i, but doesn't exist */
{
(*index) = i + 1;
return 0;
}
}