[PPL-devel] [GIT] ppl/ppl(master): PIP_Tree: avoid repeated calls to Sparse_Row::get(), in solve().

[Marco Poletti]

Module: ppl/ppl
Branch: master
Commit: 24b68b1c48e4552f1085d9a04979e610c8ca79ca
URL:    http://www.cs.unipr.it/git/gitweb.cgi?p=ppl/ppl.git;a=commit;h=24b68b1c48e4552f1085d9a04979e610c8ca79ca

Author: Marco Poletti <poletti.marco at gmail.com>
Date:   Mon Feb 14 19:45:34 2011 +0100

PIP_Tree: avoid repeated calls to Sparse_Row::get(), in solve().

---

 src/PIP_Tree.cc |    9 ++++++---
 1 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/PIP_Tree.cc b/src/PIP_Tree.cc
index 58fc66b..2660877 100644
--- a/src/PIP_Tree.cc
+++ b/src/PIP_Tree.cc
@@ -2643,20 +2643,23 @@ PIP_Solution_Node::solve(const PIP_Problem& pip,
       for (dimension_type i = num_rows; i-- > 0; ) {
         Row& s_i = tableau.s[i];
         Row& t_i = tableau.t[i];
+        Coefficient s_i_pj = s_i.get(pj);
         Row::iterator k = t_i.end();
         for (Row::const_iterator
              j = t_pivot.begin(), j_end = t_pivot.end(); j != j_end; ++j) {
           Coefficient_traits::const_reference t_pivot_j = *j;
           // Do nothing if the j-th pivot element is zero.
           if (t_pivot_j != 0) {
-            /* NOTE: s_i[pj] needs to be recomputed at each iteration,
-               as it may have been modified by tableau.scale(). */
-            product = t_pivot_j * s_i.get(pj);
+            product = t_pivot_j * s_i_pj;
             if (product % s_pivot_pj != 0) {
               // Must scale matrix to stay in integer case.
               gcd_assign(gcd, product, s_pivot_pj);
               exact_div_assign(scale_factor, s_pivot_pj, gcd);
               tableau.scale(scale_factor);
+              // s_i[pj] has been modified by scale(), so s_i_pj must be
+              // updated.
+              s_i_pj *= scale_factor;
+              PPL_ASSERT(s_i.get(pj) == s_i_pj);
               product *= scale_factor;
             }
             PPL_ASSERT(product % s_pivot_pj == 0);