From 2260e11eb019161cc861ef2b832ce3b8a92efecd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Antonio=20S=C3=A1nchez?= <cantonios@google.com>
Date: Tue, 29 Nov 2022 19:39:29 +0000
Subject: [PATCH] Fix reshape strides when input has non-zero inner stride.

---
 Eigen/src/Core/Reshaped.h |  2 +-
 test/reshape.cpp          | 19 +++++++++++++++++++
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/Eigen/src/Core/Reshaped.h b/Eigen/src/Core/Reshaped.h
index c90e61f2c8..81355ace55 100644
--- a/Eigen/src/Core/Reshaped.h
+++ b/Eigen/src/Core/Reshaped.h
@@ -251,7 +251,7 @@ class ReshapedImpl_dense<XprType, Rows, Cols, Order, true>
     EIGEN_DEVICE_FUNC EIGEN_CONSTEXPR
     inline Index outerStride() const
     {
-      return ((Flags&RowMajorBit)==RowMajorBit) ? this->cols() : this->rows();
+      return (((Flags&RowMajorBit)==RowMajorBit) ? this->cols() : this->rows()) * m_xpr.innerStride();
     }
 
   protected:
diff --git a/test/reshape.cpp b/test/reshape.cpp
index d248f01cb8..ca7a73e61e 100644
--- a/test/reshape.cpp
+++ b/test/reshape.cpp
@@ -196,6 +196,24 @@ void reshape4x4(MatType m)
   }
 }
 
+template<typename BlockType>
+void reshape_block(const BlockType& M) {
+  auto dense = M.eval();
+  Index rows = M.size() / 2;
+  Index cols = M.size() / rows;
+  VERIFY_IS_EQUAL(dense.reshaped(rows, cols), M.reshaped(rows, cols));
+  
+  for (Index i=0; i<rows; ++i) {
+    VERIFY_IS_EQUAL(dense.reshaped(rows, cols).row(i),
+                    M.reshaped(rows, cols).row(i));
+  }
+  
+  for (Index j = 0; j<cols; ++j) {
+    VERIFY_IS_EQUAL(dense.reshaped(rows, cols).col(j),
+                    M.reshaped(rows, cols).col(j));
+  }
+}
+
 EIGEN_DECLARE_TEST(reshape)
 {
   typedef Matrix<int,Dynamic,Dynamic,RowMajor> RowMatrixXi;
@@ -216,4 +234,5 @@ EIGEN_DECLARE_TEST(reshape)
 
   CALL_SUBTEST(reshape4x4(rmx));
   CALL_SUBTEST(reshape4x4(rm4));
+  CALL_SUBTEST(reshape_block(rm4.col(1)));
 }