[PPL-devel] [GIT] ppl/ppl(sparse_matrices): PIP_Tree.cc: add an optimized version of sub_assign() for sparse backends with slow insertions.

[Marco Poletti]

Module: ppl/ppl
Branch: sparse_matrices
Commit: 9ffce899fb3f1f0a87af578413d80b762009dfb6
URL:    http://www.cs.unipr.it/git/gitweb.cgi?p=ppl/ppl.git;a=commit;h=9ffce899fb3f1f0a87af578413d80b762009dfb6

Author: Marco Poletti <poletti.marco at gmail.com>
Date:   Mon Mar 22 21:23:32 2010 +0100

PIP_Tree.cc: add an optimized version of sub_assign() for sparse backends with slow insertions.

---

 src/PIP_Tree.cc |   70 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 70 insertions(+), 0 deletions(-)

diff --git a/src/PIP_Tree.cc b/src/PIP_Tree.cc
index cbe6925..d1b5dcd 100644
--- a/src/PIP_Tree.cc
+++ b/src/PIP_Tree.cc
@@ -200,6 +200,8 @@ add_mul_assign_row(PIP_Tree_Node::matrix_row_reference_type x,
 
 #endif // !defined(PPL_SPARSE_BACKEND_SLOW_INSERTIONS)
 
+#ifndef PPL_SPARSE_BACKEND_SLOW_INSERTIONS
+
 // Compute x -= y
 inline void
 sub_assign(PIP_Tree_Node::matrix_row_reference_type x,
@@ -284,6 +286,74 @@ sub_assign(PIP_Tree_Node::matrix_row_reference_type x,
   }
 }
 
+#else // !defined(PPL_SPARSE_BACKEND_SLOW_INSERTIONS)
+
+// Compute x -= y
+inline void
+sub_assign(PIP_Tree_Node::matrix_row_reference_type x,
+           PIP_Tree_Node::matrix_row_const_reference_type y) {
+  PIP_Tree_Node::matrix_row_copy_type row(x.size());
+  PIP_Tree_Node::matrix_row_copy_iterator itr = row.end();
+  PIP_Tree_Node::matrix_row_const_iterator i = x.begin();
+  PIP_Tree_Node::matrix_row_const_iterator i_end = x.end();
+  PIP_Tree_Node::matrix_const_row_const_iterator j = y.begin();
+  PIP_Tree_Node::matrix_const_row_const_iterator j_end = y.end();
+  if (i == i_end && j == j_end)
+    return;
+  if (j == j_end
+      || (i != i_end && (*i).first < (*j).first)) {
+    itr = row.find_create(*i);
+    ++i;
+  } else
+      if (i == i_end
+          || (j != j_end && (*i).first > (*j).first)) {
+        itr = row.find_create(*j);
+        neg_assign((*itr).second);
+        ++j;
+      } else {
+        PPL_ASSERT(i != i_end);
+        PPL_ASSERT(j != j_end);
+        PPL_ASSERT((*i).first == (*j).first);
+        itr = row.find_create(*i);
+        (*itr).second -= (*j).second;
+        ++i;
+        ++j;
+      }
+  PPL_ASSERT(itr != row.end());
+  while (i != i_end && j != j_end) {
+    if ((*i).first < (*j).first) {
+      itr = row.find_create(*i,itr);
+      ++i;
+    } else {
+      if ((*i).first > (*j).first) {
+        itr = row.find_create(*j,itr);
+        neg_assign((*itr).second);
+        ++j;
+      } else {
+        PPL_ASSERT((*i).first == (*j).first);
+        itr = row.find_create(*i,itr);
+        (*itr).second -= (*j).second;
+        ++i;
+        ++j;
+      }
+    }
+  }
+  while (i != i_end) {
+    itr = row.find_create(*i,itr);
+    ++i;
+  }
+  PPL_ASSERT(i == i_end);
+  while (j != j_end) {
+    itr = row.find_create(*j,itr);
+    neg_assign((*itr).second);
+    ++j;
+  }
+  PPL_ASSERT(j == j_end);
+  std::swap(row,x);
+}
+
+#endif // !defined(PPL_SPARSE_BACKEND_SLOW_INSERTIONS)
+
 // Merge constraint system to a Matrix-form context such as x = x U y
 void
 merge_assign(PIP_Tree_Node::matrix_type& x,