From dfb674a25ead137118eebf0230c4c8a4c81db5d0 Mon Sep 17 00:00:00 2001
From: Gael Guennebaud <g.gael@free.fr>
Date: Tue, 31 Mar 2015 20:17:10 +0200
Subject: [PATCH] Make reverseInPlace really work in-place.

---
 Eigen/src/Core/Reverse.h | 21 ++++++++++++++++++++-
 test/array_reverse.cpp   | 22 +++++++++++++++++-----
 2 files changed, 37 insertions(+), 6 deletions(-)

diff --git a/Eigen/src/Core/Reverse.h b/Eigen/src/Core/Reverse.h
index 291300a4a..b3fba9704 100644
--- a/Eigen/src/Core/Reverse.h
+++ b/Eigen/src/Core/Reverse.h
@@ -210,7 +210,26 @@ DenseBase<Derived>::reverse() const
 template<typename Derived>
 inline void DenseBase<Derived>::reverseInPlace()
 {
-  derived() = derived().reverse().eval();
+  if(cols()>rows())
+  {
+    Index half = cols()/2;
+    leftCols(half).swap(rightCols(half).reverse());
+    if((cols()%2)==1)
+    {
+      Index half2 = rows()/2;
+      col(half).head(half2).swap(col(half).tail(half2).reverse());
+    }
+  }
+  else
+  {
+    Index half = rows()/2;
+    topRows(half).swap(bottomRows(half).reverse());
+    if((rows()%2)==1)
+    {
+      Index half2 = cols()/2;
+      row(half).head(half2).swap(row(half).tail(half2).reverse());
+    }
+  }
 }
 
 } // end namespace Eigen
diff --git a/test/array_reverse.cpp b/test/array_reverse.cpp
index fbe7a9901..9ba19246b 100644
--- a/test/array_reverse.cpp
+++ b/test/array_reverse.cpp
@@ -24,7 +24,7 @@ template<typename MatrixType> void reverse(const MatrixType& m)
 
   // this test relies a lot on Random.h, and there's not much more that we can do
   // to test it, hence I consider that we will have tested Random.h
-  MatrixType m1 = MatrixType::Random(rows, cols);
+  MatrixType m1 = MatrixType::Random(rows, cols), m2;
   VectorType v1 = VectorType::Random(rows);
 
   MatrixType m1_r = m1.reverse();
@@ -96,6 +96,18 @@ template<typename MatrixType> void reverse(const MatrixType& m)
 
   m1.reverse()(r, c) = x;
   VERIFY_IS_APPROX(x, m1(rows - 1 - r, cols - 1 - c));
+  
+  m2 = m1;
+  m2.reverseInPlace();
+  VERIFY_IS_APPROX(m2,m1.reverse().eval());
+  
+  m2 = m1;
+  m2.col(0).reverseInPlace();
+  VERIFY_IS_APPROX(m2.col(0),m1.col(0).reverse().eval());
+  
+  m2 = m1;
+  m2.row(0).reverseInPlace();
+  VERIFY_IS_APPROX(m2.row(0),m1.row(0).reverse().eval());
 
   /*
   m1.colwise().reverse()(r, c) = x;
@@ -113,11 +125,11 @@ void test_array_reverse()
     CALL_SUBTEST_2( reverse(Matrix2f()) );
     CALL_SUBTEST_3( reverse(Matrix4f()) );
     CALL_SUBTEST_4( reverse(Matrix4d()) );
-    CALL_SUBTEST_5( reverse(MatrixXcf(3, 3)) );
-    CALL_SUBTEST_6( reverse(MatrixXi(6, 3)) );
-    CALL_SUBTEST_7( reverse(MatrixXcd(20, 20)) );
+    CALL_SUBTEST_5( reverse(MatrixXcf(internal::random<int>(1,EIGEN_TEST_MAX_SIZE), internal::random<int>(1,EIGEN_TEST_MAX_SIZE))) );
+    CALL_SUBTEST_6( reverse(MatrixXi(internal::random<int>(1,EIGEN_TEST_MAX_SIZE), internal::random<int>(1,EIGEN_TEST_MAX_SIZE))) );
+    CALL_SUBTEST_7( reverse(MatrixXcd(internal::random<int>(1,EIGEN_TEST_MAX_SIZE), internal::random<int>(1,EIGEN_TEST_MAX_SIZE))) );
     CALL_SUBTEST_8( reverse(Matrix<float, 100, 100>()) );
-    CALL_SUBTEST_9( reverse(Matrix<float,Dynamic,Dynamic,RowMajor>(6,3)) );
+    CALL_SUBTEST_9( reverse(Matrix<float,Dynamic,Dynamic,RowMajor>(internal::random<int>(1,EIGEN_TEST_MAX_SIZE), internal::random<int>(1,EIGEN_TEST_MAX_SIZE))) );
   }
 #ifdef EIGEN_TEST_PART_3
   Vector4f x; x << 1, 2, 3, 4;