Implement swap using evaluators.

Eigen/src/Core/AssignEvaluator.h

@@ -404,7 +404,7 @@ struct copy_using_evaluator_impl<DstXprType, SrcXprType, LinearVectorizedTravers
       dstAlignment = PacketTraits::AlignedOnScalar ? Aligned : dstIsAligned,
       srcAlignment = copy_using_evaluator_traits<DstXprType,SrcXprType>::JointAlignment
     };
-    const Index alignedStart = dstIsAligned ? 0 : first_aligned(&dst.coeffRef(0), size);
+    const Index alignedStart = dstIsAligned ? 0 : first_aligned(&dstEvaluator.coeffRef(0), size);
     const Index alignedEnd = alignedStart + ((size-alignedStart)/packetSize)*packetSize;
 
     unaligned_copy_using_evaluator_impl<dstIsAligned!=0>::run(dstEvaluator, srcEvaluator, 0, alignedStart);
@@ -614,6 +614,16 @@ const DstXprType& copy_using_evaluator(const DstXprType& dst, const SrcXprType&
   return dst;
 }
 
+// Based on DenseBase::swap()
+// TODO: Chech whether we need to do something special for swapping two
+//       Arrays or Matrices.
+
+template<typename DstXprType, typename SrcXprType>
+void swap_using_evaluator(const DstXprType& dst, const SrcXprType& src)
+{
+  copy_using_evaluator(SwapWrapper<DstXprType>(const_cast<DstXprType&>(dst)), src);
+}
+
 } // namespace internal
 
 #endif // EIGEN_ASSIGN_EVALUATOR_H

Eigen/src/Core/CoreEvaluators.h

@@ -65,7 +65,7 @@ struct evaluator_impl_base
   {
     Index row = rowIndexByOuterInner(outer, inner); 
     Index col = colIndexByOuterInner(outer, inner); 
-    derived().coeffRef(row, col) = other.coeff(row, col);
+    derived().copyCoeff(row, col, other);
   }
 
   template<typename OtherEvaluatorType>
@@ -86,8 +86,7 @@ struct evaluator_impl_base
   {
     Index row = rowIndexByOuterInner(outer, inner); 
     Index col = colIndexByOuterInner(outer, inner); 
-    derived().template writePacket<StoreMode>(row, col, 
+    derived().template copyPacket<StoreMode, LoadMode>(row, col, other);
-      other.template packet<LoadMode>(row, col));
   }
 
   template<int StoreMode, int LoadMode, typename OtherEvaluatorType>
@@ -1017,6 +1016,75 @@ private:
 };
 
 
+// ---------- SwapWrapper ----------
+
+template<typename ArgType>
+struct evaluator_impl<SwapWrapper<ArgType> >
+  : evaluator_impl_base<SwapWrapper<ArgType> >
+{
+  typedef SwapWrapper<ArgType> XprType;
+
+  evaluator_impl(const XprType& swapWrapper) 
+    : m_argImpl(swapWrapper.expression())
+  { }
+ 
+  typedef typename XprType::Index Index;
+  typedef typename XprType::Scalar Scalar;
+  typedef typename XprType::Packet Packet;
+
+  Scalar& coeffRef(Index row, Index col)
+  {
+    return m_argImpl.coeffRef(row, col);
+  }
+  
+  inline Scalar& coeffRef(Index index)
+  {
+    return m_argImpl.coeffRef(index);
+  }
+
+  template<typename OtherEvaluatorType>
+  void copyCoeff(Index row, Index col, const OtherEvaluatorType& other)
+  {
+    OtherEvaluatorType& nonconst_other = const_cast<OtherEvaluatorType&>(other);
+    Scalar tmp = m_argImpl.coeff(row, col);
+    m_argImpl.coeffRef(row, col) = nonconst_other.coeff(row, col);
+    nonconst_other.coeffRef(row, col) = tmp;
+  }
+
+  template<typename OtherEvaluatorType>
+  void copyCoeff(Index index, const OtherEvaluatorType& other)
+  {
+    OtherEvaluatorType& nonconst_other = const_cast<OtherEvaluatorType&>(other);
+    Scalar tmp = m_argImpl.coeff(index);
+    m_argImpl.coeffRef(index) = nonconst_other.coeff(index);
+    nonconst_other.coeffRef(index) = tmp;
+  }
+
+  template<int StoreMode, int LoadMode, typename OtherEvaluatorType>
+  void copyPacket(Index row, Index col, const OtherEvaluatorType& other)
+  {
+    OtherEvaluatorType& nonconst_other = const_cast<OtherEvaluatorType&>(other);
+    Packet tmp = m_argImpl.template packet<StoreMode>(row, col);
+    m_argImpl.template writePacket<StoreMode>
+      (row, col, nonconst_other.template packet<LoadMode>(row, col));
+    nonconst_other.template writePacket<LoadMode>(row, col, tmp);
+  }
+
+  template<int StoreMode, int LoadMode, typename OtherEvaluatorType>
+  void copyPacket(Index index, const OtherEvaluatorType& other)
+  {
+    OtherEvaluatorType& nonconst_other = const_cast<OtherEvaluatorType&>(other);
+    Packet tmp = m_argImpl.template packet<StoreMode>(index);
+    m_argImpl.template writePacket<StoreMode>
+      (index, nonconst_other.template packet<LoadMode>(index));
+    nonconst_other.template writePacket<LoadMode>(index, tmp);
+  }
+
+protected:
+  typename evaluator<ArgType>::type m_argImpl;
+};
+
+
 } // namespace internal
 
 #endif // EIGEN_COREEVALUATORS_H

Eigen/src/Core/Swap.h

@@ -119,6 +119,8 @@ template<typename ExpressionType> class SwapWrapper
       _other.template writePacket<LoadMode>(index, tmp);
     }
 
+    ExpressionType& expression() const { return m_expression; }
+
   protected:
     ExpressionType& m_expression;
 };

test/evaluators.cpp

@@ -214,5 +214,27 @@ void test_evaluators()
 
   copy_using_evaluator(mat1.diagonal<-1>(), mat1.diagonal(1));
   mat2.diagonal<-1>() = mat2.diagonal(1);
- VERIFY_IS_APPROX(mat1, mat2);
+  VERIFY_IS_APPROX(mat1, mat2);
+  
+  {
+    // test swapping
+    MatrixXd mat1, mat2, mat1ref, mat2ref;
+    mat1ref = mat1 = MatrixXd::Random(6, 6);
+    mat2ref = mat2 = 2 * mat1 + MatrixXd::Identity(6, 6);
+    swap_using_evaluator(mat1, mat2);
+    mat1ref.swap(mat2ref);
+    VERIFY_IS_APPROX(mat1, mat1ref);
+    VERIFY_IS_APPROX(mat2, mat2ref);
+
+    swap_using_evaluator(mat1.block(0, 0, 3, 3), mat2.block(3, 3, 3, 3));
+    mat1ref.block(0, 0, 3, 3).swap(mat2ref.block(3, 3, 3, 3));
+    VERIFY_IS_APPROX(mat1, mat1ref);
+    VERIFY_IS_APPROX(mat2, mat2ref);
+
+    swap_using_evaluator(mat1.row(2), mat2.col(3).transpose());
+    mat1.row(2).swap(mat2.col(3).transpose());
+    VERIFY_IS_APPROX(mat1, mat1ref);
+    VERIFY_IS_APPROX(mat2, mat2ref);
+  }
+    
 }