Ciao,
On Sun, August 16, 2015 11:50 pm, Torbjörn Granlund wrote:
> On Sat, August 15, 2015 12:37 pm, Vincent Delecroix wrote:
> > it would be convenient to have a GMP function
> >
> > int mpq_cmp_z(mpq_t, mpz_t)
> We might consider some code sharing between the mpq_cmp and this
> function, they look very similar.
Maybe I've found a good sharing strategy...
static int
mpq_cmp_maybe_z (mpq_srcptr op1, mpq_srcptr op2, int op2_is_mpz)
{
...
}
int
mpq_cmp (mpq_srcptr op1, mpq_srcptr op2)
{
ASSERT (SIZ(DEN(op2) != 0));
return mpq_cmp_maybe_z (op1, op2,
(SIZ(DEN(op2)) | PTR(DEN(op2))[0]) == CNST_LIMB(1));
}
int
mpq_cmp_z (mpq_srcptr op1, mpz_srcptr op2)
{
return mpq_cmp_maybe_z (op1, (mpq_srcptr) op2, 1);
}
This way gcc compiles the mpq_cmp_z function (on amd64) as:
movl $1, %edx
jmp mpq_cmp_maybe_z
Is casting an mpz to an mpq, then accessing only the NUM() part of it,
portable?
I attach the proposed code, it adds four branches to the typical mpq_cmp
flow. One of them (checking if op1 is an integer) is not needed for
correctness. Please review!
Regards,
m
--
http://bodrato.it/papers//* mpq_cmp(u,v) -- Compare U, V. Return positive, zero, or negative
based on if U > V, U == V, or U < V.
Copyright 1991, 1994, 1996, 2001, 2002, 2005, 2015 Free Software Foundation, Inc.
This file is part of the GNU MP Library.
The GNU MP Library is free software; you can redistribute it and/or modify
it under the terms of either:
* the GNU Lesser General Public License as published by the Free
Software Foundation; either version 3 of the License, or (at your
option) any later version.
or
* the GNU General Public License as published by the Free Software
Foundation; either version 2 of the License, or (at your option) any
later version.
or both in parallel, as here.
The GNU MP Library 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 General Public License
for more details.
You should have received copies of the GNU General Public License and the
GNU Lesser General Public License along with the GNU MP Library. If not,
see https://www.gnu.org/licenses/. */
#include "gmp.h"
#include "gmp-impl.h"
#include "longlong.h"
static int
mpq_cmp_maybe_z (mpq_srcptr op1, mpq_srcptr op2, int op2_is_mpz)
{
mp_size_t num1_size = SIZ(NUM(op1));
mp_size_t den1_size = SIZ(DEN(op1));
mp_size_t num2_size = SIZ(NUM(op2));
mp_size_t den2_size = op2_is_mpz ? 0 : SIZ(DEN(op2));
mp_size_t tmp1_size, tmp2_size;
mp_ptr tmp1_ptr, tmp2_ptr;
mp_size_t num1_sign;
mp_limb_t d1h;
int cc;
TMP_DECL;
/* need canonical signs to get right result */
ASSERT (den1_size > 0);
ASSERT (op2_is_mpz || den2_size > 0);
if (num1_size == 0)
return -num2_size;
if (num2_size == 0)
return num1_size;
if ((num1_size ^ num2_size) < 0) /* I.e. are the signs different? */
return num1_size;
d1h = PTR(DEN(op1))[den1_size - 1]; /* THINK: Does storing d1h make sense? */
num1_sign = num1_size;
#if 1
if (op2_is_mpz == (den1_size | d1h)) /* Both ops are integers */
/* FIXME: check sizes, then use mpn_cmp */
return mpz_cmp (NUM (op1), NUM (op2));
#else
if (CNST_LIMB (1) == (den1_size | d1h)) /* op1 is an integer */
{
if (op2_is_mpz) /* Both integers */
return mpz_cmp (NUM (op1), NUM (op2));
MPQ_SRCPTR_SWAP (op1, op2);
num1_size = num2_size;
den1_size = den2_size;
num2_size = num1_sign;
den2_size = 0;
num1_sign = - num1_sign;
op2_is_mpz = 1;
d1h = PTR(DEN(op1))[den1_size - 1];
}
#endif
num1_size = ABS (num1_size);
num2_size = ABS (num2_size);
tmp1_size = num1_size + den2_size;
tmp2_size = num2_size + den1_size;
/* 1. Check to see if we can tell which operand is larger by just looking at
the number of limbs. */
/* NUM1 x DEN2 is either TMP1_SIZE limbs or TMP1_SIZE-1 limbs.
Same for NUM1 x DEN1 with respect to TMP2_SIZE. */
if (tmp1_size + op2_is_mpz > tmp2_size + 1)
/* NUM1 x DEN2 is surely larger in magnitude than NUM2 x DEN1. */
return num1_sign;
if (tmp2_size > tmp1_size + 1)
/* NUM1 x DEN2 is surely smaller in magnitude than NUM2 x DEN1. */
return -num1_sign;
/* 2. Same, but compare the number of significant bits. */
{
int cnt1, cnt2;
mp_bitcnt_t bits1, bits2;
count_leading_zeros (cnt1, PTR(NUM(op1))[num1_size - 1]);
bits1 = tmp1_size * GMP_NUMB_BITS - cnt1; /* + GMP_NAIL_BITS */
if (op2_is_mpz == 0)
{
count_leading_zeros (cnt2, PTR(DEN(op2))[den2_size - 1]);
bits1 -= cnt2 - GMP_NAIL_BITS;
}
count_leading_zeros (cnt1, PTR(NUM(op2))[num2_size - 1]);
count_leading_zeros (cnt2, d1h);
bits2 = tmp2_size * GMP_NUMB_BITS - cnt1 - cnt2 + GMP_NAIL_BITS; /* + GMP_NAIL_BITS */
if (bits1 + op2_is_mpz > bits2 + 1)
return num1_sign;
if (bits2 > bits1 + 1)
return -num1_sign;
}
/* 3. Finally, cross multiply and compare. */
TMP_MARK;
if (op2_is_mpz)
{
tmp2_ptr = TMP_ALLOC_LIMBS (tmp2_size);
tmp1_ptr = PTR(NUM(op1));
}
else
{
TMP_ALLOC_LIMBS_2 (tmp1_ptr,tmp1_size, tmp2_ptr,tmp2_size);
if (num1_size >= den2_size)
tmp1_size -= 0 == mpn_mul (tmp1_ptr,
PTR(NUM(op1)), num1_size,
PTR(DEN(op2)), den2_size);
else
tmp1_size -= 0 == mpn_mul (tmp1_ptr,
PTR(DEN(op2)), den2_size,
PTR(NUM(op1)), num1_size);
}
if (num2_size >= den1_size)
tmp2_size -= 0 == mpn_mul (tmp2_ptr,
PTR(NUM(op2)), num2_size,
PTR(DEN(op1)), den1_size);
else
tmp2_size -= 0 == mpn_mul (tmp2_ptr,
PTR(DEN(op1)), den1_size,
PTR(NUM(op2)), num2_size);
cc = tmp1_size - tmp2_size != 0
? tmp1_size - tmp2_size : mpn_cmp (tmp1_ptr, tmp2_ptr, tmp1_size);
TMP_FREE;
return num1_sign < 0 ? -cc : cc;
}
int
mpq_cmp (mpq_srcptr op1, mpq_srcptr op2)
{
ASSERT (SIZ(DEN(op2) != 0));
return mpq_cmp_maybe_z (op1, op2, (SIZ(DEN(op2)) | PTR(DEN(op2))[0]) == CNST_LIMB(1));
}
int
mpq_cmp_z (mpq_srcptr op1, mpz_srcptr op2)
{
return mpq_cmp_maybe_z (op1, (mpq_srcptr) op2, 1);
}_______________________________________________
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