From e3c0ae5b9b52120cfcf58f09a74b62827e2df2e1 Mon Sep 17 00:00:00 2001
From: Laurent Perron <lperron@google.com>
Date: Thu, 22 Aug 2019 13:15:29 +0200
Subject: [PATCH] improve glop internals

---
 ortools/glop/basis_representation.cc |  3 +--
 ortools/glop/lu_factorization.cc     | 11 ++++++++---
 ortools/glop/lu_factorization.h      |  3 ++-
 ortools/glop/revised_simplex.cc      |  4 ++++
 ortools/glop/revised_simplex.h       |  1 +
 5 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/ortools/glop/basis_representation.cc b/ortools/glop/basis_representation.cc
index bb2401e793..eb06b31510 100644
--- a/ortools/glop/basis_representation.cc
+++ b/ortools/glop/basis_representation.cc
@@ -344,8 +344,7 @@ const DenseColumn& BasisFactorization::RightSolveForTau(
       // Once used, the intermediate result is overwritten, so
       // RightSolveForTau() can no longer use the optimized algorithm.
       tau_computation_can_be_optimized_ = false;
-      lu_factorization_.RightSolveLWithPermutedInput(a.values, &tau_.values);
-      tau_.non_zeros.clear();
+      lu_factorization_.RightSolveLWithPermutedInput(a.values, &tau_);
     } else {
       ClearAndResizeVectorWithNonZeros(compact_matrix_.num_rows(), &tau_);
       lu_factorization_.RightSolveLForScatteredColumn(a, &tau_);
diff --git a/ortools/glop/lu_factorization.cc b/ortools/glop/lu_factorization.cc
index 341206bff4..80bb4779ac 100644
--- a/ortools/glop/lu_factorization.cc
+++ b/ortools/glop/lu_factorization.cc
@@ -182,11 +182,16 @@ bool AreEqualWithPermutation(const DenseColumn& a, const DenseColumn& b,
 }  // namespace
 
 void LuFactorization::RightSolveLWithPermutedInput(const DenseColumn& a,
-                                                   DenseColumn* x) const {
+                                                   ScatteredColumn* x) const {
   SCOPED_TIME_STAT(&stats_);
   if (!is_identity_factorization_) {
-    DCHECK(AreEqualWithPermutation(a, *x, row_perm_));
-    lower_.LowerSolve(x);
+    DCHECK(AreEqualWithPermutation(a, x->values, row_perm_));
+    lower_.ComputeRowsToConsiderInSortedOrder(&x->non_zeros);
+    if (x->non_zeros.empty()) {
+      lower_.LowerSolve(&x->values);
+    } else {
+      lower_.HyperSparseSolve(&x->values, &x->non_zeros);
+    }
   }
 }
 
diff --git a/ortools/glop/lu_factorization.h b/ortools/glop/lu_factorization.h
index d1365f3a9a..b91465854f 100644
--- a/ortools/glop/lu_factorization.h
+++ b/ortools/glop/lu_factorization.h
@@ -115,7 +115,8 @@ class LuFactorization {
 
   // Specialized version of RightSolveLWithNonZeros() where x is originaly equal
   // to 'a' permuted by row_perm_. Note that 'a' is only used for DCHECK.
-  void RightSolveLWithPermutedInput(const DenseColumn& a, DenseColumn* x) const;
+  void RightSolveLWithPermutedInput(const DenseColumn& a,
+                                    ScatteredColumn* x) const;
 
   // Specialized version of LeftSolveU() for an unit right-hand side.
   // non_zeros will either be cleared or set to the non zeros of the results.
diff --git a/ortools/glop/revised_simplex.cc b/ortools/glop/revised_simplex.cc
index 9df4b86919..9b3ef44e67 100644
--- a/ortools/glop/revised_simplex.cc
+++ b/ortools/glop/revised_simplex.cc
@@ -394,6 +394,10 @@ Fractional RevisedSimplex::GetReducedCost(ColIndex col) const {
   return solution_reduced_costs_[col];
 }
 
+const DenseRow& RevisedSimplex::GetReducedCosts() const {
+  return solution_reduced_costs_;
+}
+
 Fractional RevisedSimplex::GetDualValue(RowIndex row) const {
   return solution_dual_values_[row];
 }
diff --git a/ortools/glop/revised_simplex.h b/ortools/glop/revised_simplex.h
index 3afc2cb664..d7cfb0f197 100644
--- a/ortools/glop/revised_simplex.h
+++ b/ortools/glop/revised_simplex.h
@@ -190,6 +190,7 @@ class RevisedSimplex {
   int64 GetNumberOfIterations() const;
   Fractional GetVariableValue(ColIndex col) const;
   Fractional GetReducedCost(ColIndex col) const;
+  const DenseRow& GetReducedCosts() const;
   Fractional GetDualValue(RowIndex row) const;
   Fractional GetConstraintActivity(RowIndex row) const;
   VariableStatus GetVariableStatus(ColIndex col) const;