fixed efficiency bug for small divisor (division had same cost than for

divisor of the same size than the result)


git-svn-id: svn://scm.gforge.inria.fr/svn/mpfr/trunk@3963 280ebfd0-de03-0410-8827-d642c229c3f4

1 files changed, 8 insertions, 9 deletions

diff --git a/div.c b/div.c
index 81713ec7c..35f3bbca3 100644
--- a/div.c
+++ b/div.c
@@ -251,7 +251,7 @@ mpfr_div (mpfr_ptr q, mpfr_srcptr u, mpfr_srcptr v, mp_rnd_t rnd_mode)
          sticky bits */
       qsize = q0size + 1;
       /* need to allocate memory for the quotient */
-      qp = (mp_ptr) MPFR_TMP_ALLOC (qsize*sizeof(mp_limb_t));
+      qp = (mp_ptr) MPFR_TMP_ALLOC (qsize * sizeof(mp_limb_t));
     }
   else
     {
@@ -261,7 +261,7 @@ mpfr_div (mpfr_ptr q, mpfr_srcptr u, mpfr_srcptr v, mp_rnd_t rnd_mode)
   qqsize = qsize + qsize;
 
   /* prepare the dividend */
-  ap = (mp_ptr) MPFR_TMP_ALLOC (qqsize*sizeof(mp_limb_t));
+  ap = (mp_ptr) MPFR_TMP_ALLOC (qqsize * sizeof(mp_limb_t));
   if (MPFR_LIKELY(qqsize > usize)) /* use the full dividend */
     {
       k = qqsize - usize; /* k > 0 */
@@ -298,19 +298,18 @@ mpfr_div (mpfr_ptr q, mpfr_srcptr u, mpfr_srcptr v, mp_rnd_t rnd_mode)
           MPN_COPY(bp, vp, vsize);
         }
       sticky_v = sticky_v || mpn_cmpzero (vp, k);
+      k = 0;
     }
-  else /* vsize < qsize */
+  else /* vsize < qsize: small divisor case */
     {
+      bp = vp;
       k = qsize - vsize;
-      bp = (mp_ptr) MPFR_TMP_ALLOC (qsize * sizeof(mp_limb_t));
-      MPN_COPY(bp + k, vp, vsize);
-      MPN_ZERO(bp, k);
     }
 
   /* we now can perform the division */
-  qh = mpn_divrem (qp, 0, ap, qqsize, bp, qsize);
+  qh = mpn_divrem (qp, 0, ap + k, qqsize - k, bp, qsize - k);
   /* warning: qh may be 1 if u1 == v1, but u < v */
-#ifdef DEBUG
+#ifdef DEBUG2
   printf ("q="); mpn_print (qp, qsize);
   printf ("r="); mpn_print (ap, qsize);
 #endif
@@ -402,7 +401,7 @@ mpfr_div (mpfr_ptr q, mpfr_srcptr u, mpfr_srcptr v, mp_rnd_t rnd_mode)
               mp_ptr sp;
               int cmp_s_r;
 
-              sp = (mp_ptr) MPFR_TMP_ALLOC (vsize*sizeof(mp_limb_t));
+              sp = (mp_ptr) MPFR_TMP_ALLOC (vsize * sizeof(mp_limb_t));
               k = vsize - qsize;
               /* sp <- {qp, qsize} * {vp, vsize-qsize} */
               qp[0] ^= sticky3orig; /* restore original quotient */