From cfca7f71fea444f46249375106e5f64d83533be8 Mon Sep 17 00:00:00 2001
From: Gael Guennebaud <g.gael@free.fr>
Date: Sat, 18 Oct 2008 11:11:10 +0000
Subject: sparse module: much much faster transposition code

---
 Eigen/src/Sparse/SparseMatrix.h  | 54 +++++++++++++++++++++++++++++++++++++---
 Eigen/src/Sparse/SparseProduct.h |  5 +++-
 2 files changed, 54 insertions(+), 5 deletions(-)

(limited to 'Eigen')

diff --git a/Eigen/src/Sparse/SparseMatrix.h b/Eigen/src/Sparse/SparseMatrix.h
index e3b224d7f..5dd1f1365 100644
--- a/Eigen/src/Sparse/SparseMatrix.h
+++ b/Eigen/src/Sparse/SparseMatrix.h
@@ -65,6 +65,7 @@ class SparseMatrix
     enum {
       RowMajor = SparseBase::RowMajor
     };
+    typedef SparseMatrix<Scalar,(Flags&~RowMajorBit)|(RowMajor?RowMajorBit:0)> TransposedSparseMatrix;
 
     int m_outerSize;
     int m_innerSize;
@@ -225,8 +226,7 @@ class SparseMatrix
       else
       {
         resize(other.rows(), other.cols());
-        for (int j=0; j<=m_outerSize; ++j)
-          m_outerIndex[j] = other.m_outerIndex[j];
+        memcpy(m_outerIndex, other.m_outerIndex, (m_outerSize+1)*sizeof(int));
         m_data = other.m_data;
       }
       return *this;
@@ -235,8 +235,54 @@ class SparseMatrix
     template<typename OtherDerived>
     inline SparseMatrix& operator=(const MatrixBase<OtherDerived>& other)
     {
-//       std::cout << "SparseMatrix& operator=(const MatrixBase<OtherDerived>& other)\n";
-      return SparseMatrixBase<SparseMatrix>::operator=(other.derived());
+      const bool needToTranspose = (Flags & RowMajorBit) != (OtherDerived::Flags & RowMajorBit);
+      if (needToTranspose)
+      {
+        // two passes algorithm:
+        //  1 - compute the number of coeffs per dest inner vector
+        //  2 - do the actual copy/eval
+        // Since each coeff of the rhs has to be evaluated twice, let's evauluate it if needed
+        typedef typename ei_nested<OtherDerived,2>::type OtherCopy;
+        OtherCopy otherCopy(other.derived());
+        typedef typename ei_cleantype<OtherCopy>::type _OtherCopy;
+
+        resize(other.rows(), other.cols());
+        Map<VectorXi>(m_outerIndex,outerSize()).setZero();
+        // pass 1
+        // FIXME the above copy could be merged with that pass
+        for (int j=0; j<otherCopy.outerSize(); ++j)
+          for (typename _OtherCopy::InnerIterator it(otherCopy, j); it; ++it)
+            m_outerIndex[it.index()]++;
+
+        // prefix sum
+        int count = 0;
+        VectorXi positions(outerSize());
+        for (int j=0; j<outerSize(); ++j)
+        {
+          int tmp = m_outerIndex[j];
+          m_outerIndex[j] = count;
+          positions[j] = count;
+          count += tmp;
+        }
+        m_outerIndex[outerSize()] = count;
+        // alloc
+        m_data.resize(count);
+        // pass 2
+        for (int j=0; j<otherCopy.outerSize(); ++j)
+          for (typename _OtherCopy::InnerIterator it(otherCopy, j); it; ++it)
+          {
+            int pos = positions[it.index()]++;
+            m_data.index(pos) = j;
+            m_data.value(pos) = it.value();
+          }
+
+        return *this;
+      }
+      else
+      {
+        // there is no special optimization
+        return SparseMatrixBase<SparseMatrix>::operator=(other.derived());
+      }
     }
 
     friend std::ostream & operator << (std::ostream & s, const SparseMatrix& m)
diff --git a/Eigen/src/Sparse/SparseProduct.h b/Eigen/src/Sparse/SparseProduct.h
index 28b05f6a0..c430ed928 100644
--- a/Eigen/src/Sparse/SparseProduct.h
+++ b/Eigen/src/Sparse/SparseProduct.h
@@ -169,7 +169,10 @@ struct ei_sparse_product_selector<Lhs,Rhs,ResultType,ColMajor,ColMajor,ColMajor>
         }
       }
       for (typename AmbiVector<Scalar>::Iterator it(tempVector); it; ++it)
-        res.fill(it.index(), j) = it.value();
+        if (ResultType::Flags&RowMajorBit)
+          res.fill(j,it.index()) = it.value();
+        else
+          res.fill(it.index(), j) = it.value();
     }
     res.endFill();
   }
-- 
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