summaryrefslogtreecommitdiff
path: root/mpf
diff options
context:
space:
mode:
Diffstat (limited to 'mpf')
-rw-r--r--mpf/set_q.c76
1 files changed, 20 insertions, 56 deletions
diff --git a/mpf/set_q.c b/mpf/set_q.c
index c5739b2ab..dbe8818b0 100644
--- a/mpf/set_q.c
+++ b/mpf/set_q.c
@@ -1,6 +1,6 @@
/* mpf_set_q (mpf_t rop, mpq_t op) -- Convert the rational op to the float rop.
-Copyright 1996, 1999, 2001, 2002, 2004, 2005 Free Software Foundation, Inc.
+Copyright 1996, 1999, 2001, 2002, 2004, 2005, 2016 Free Software Foundation, Inc.
This file is part of the GNU MP Library.
@@ -28,47 +28,28 @@ 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 <stdio.h> /* for NULL */
#include "gmp.h"
#include "gmp-impl.h"
-#include "longlong.h"
-/* As usual the aim is to produce PREC(r) limbs, with the high non-zero.
- The basic mpn_tdiv_qr produces a quotient of nsize-dsize+1 limbs, with
- either the high or second highest limb non-zero. We arrange for
- nsize-dsize+1 to equal prec+1, hence giving either prec or prec+1 result
- limbs at PTR(r).
+/* As usual the aim is to produce PREC(r) limbs, with the high non-zero. The
+ basic mpn_div_q produces a quotient of nsize-dsize+1 limbs, with either the
+ high or second highest limb non-zero. We arrange for nsize-dsize+1 to equal
+ prec+1, hence giving either prec or prec+1 result limbs at PTR(r).
- nsize-dsize+1 == prec+1 is achieved by adjusting num(q), either dropping
- low limbs if it's too big, or padding with low zeros if it's too small.
- The full given den(q) is always used.
+ nsize-dsize+1 == prec+1 is achieved by adjusting num(q), either dropping low
+ limbs if it's too big, or padding with low zeros if it's too small. The
+ full given den(q) is always used.
- We cannot truncate den(q), because even when it's much bigger than prec
- the last limbs can still influence the final quotient. Often they don't,
- but we leave optimization of that to a prospective quotient-only mpn
- division.
-
- Not done:
-
- If den(q) is a power of 2 then we may end up with low zero limbs on the
- result. But nothing is done about this, since it should be unlikely on
- random data, and can be left to an application to call mpf_div_2exp if it
- might occur with any frequency.
+ We cannot truncate den(q), because even when it's much bigger than prec the
+ last limbs can still influence the final quotient. Often they don't, but we
+ leave optimization of that to mpn_div_q.
Enhancements:
- The high quotient limb is non-zero when high{np,dsize} >= {dp,dsize}. We
+ The high quotient limb is non-zero when high{np,dsize} > {dp,dsize}. We
could make that comparison and use qsize==prec instead of qsize==prec+1,
- to save one limb in the division.
-
- Future:
-
- If/when mpn_tdiv_qr supports its qxn parameter we can use that instead of
- padding n with zeros in temporary space.
-
- If/when a quotient-only division exists it can be used here immediately.
- remp is only to satisfy mpn_tdiv_qr, the remainder is not used. */
+ to save one limb in the division. */
void
mpf_set_q (mpf_t r, mpq_srcptr q)
@@ -76,7 +57,7 @@ mpf_set_q (mpf_t r, mpq_srcptr q)
mp_srcptr np, dp;
mp_size_t prec, nsize, dsize, qsize, prospective_qsize, tsize, zeros;
mp_size_t sign_quotient, high_zero;
- mp_ptr qp, tp, remp;
+ mp_ptr qp, tp;
mp_exp_t exp;
TMP_DECL;
@@ -106,42 +87,25 @@ mpf_set_q (mpf_t r, mpq_srcptr q)
exp = prospective_qsize; /* ie. number of integer limbs */
qsize = prec + 1; /* desired q */
- zeros = qsize - prospective_qsize; /* n zeros to get desired qsize */
- tsize = nsize + zeros; /* possible copy of n */
-
- if (WANT_TMP_DEBUG)
- {
- /* separate alloc blocks, for malloc debugging */
- remp = TMP_ALLOC_LIMBS (dsize);
- tp = NULL;
- if (zeros > 0)
- tp = TMP_ALLOC_LIMBS (tsize);
- }
- else
- {
- /* one alloc with a conditionalized size, for efficiency */
- mp_size_t size = dsize + (zeros > 0 ? tsize : 0);
- remp = TMP_ALLOC_LIMBS (size);
- tp = remp + dsize;
- }
+ zeros = qsize - prospective_qsize; /* n zeros to get desired qsize */
+ tsize = nsize + zeros; /* size of intermediate numerator */
+ tp = TMP_ALLOC_LIMBS (tsize + 1); /* +1 for mpn_div_q's scratch */
if (zeros > 0)
{
/* pad n with zeros into temporary space */
MPN_ZERO (tp, zeros);
MPN_COPY (tp+zeros, np, nsize);
- np = tp;
- nsize = tsize;
+ np = tp; /* mpn_div_q allows this overlap */
}
else
{
/* shorten n to get desired qsize */
- nsize += zeros;
np -= zeros;
}
- ASSERT (nsize-dsize+1 == qsize);
- mpn_tdiv_qr (qp, remp, (mp_size_t) 0, np, nsize, dp, dsize);
+ ASSERT (tsize-dsize+1 == qsize);
+ mpn_div_q (qp, np, tsize, dp, dsize, tp);
/* strip possible zero high limb */
high_zero = (qp[qsize-1] == 0);