[fix issue#9976] The assignment problem in NDArray

include/mxnet/ndarray.h

@@ -325,6 +325,10 @@ class NDArray {
  inline Engine::VarHandle var() const {
  return ptr_->var;
  }
+ /*! \return byte offset in chunk of the ndarray*/
+ inline size_t byte_offset() const {
+ return byte_offset_;
+ }
  /*!
  * \brief save the content into binary stream
  * \param strm the output stream

src/ndarray/ndarray.cc

@@ -1128,7 +1128,7 @@ void CopyFromToImpl(const NDArray& from, const NDArray& to,
 }
 
 void CopyFromTo(const NDArray& from, const NDArray& to, int priority) {
- if (from.var() == to.var()) {
+ if (from.var() == to.var() && from.byte_offset() == to.byte_offset()) {
  // skip to copy to itself
  return;
  }

tests/python/unittest/test_ndarray.py

@@ -1099,6 +1099,35 @@ def test_assign_float_value_to_ndarray():
  b[0] = a[0]
  assert same(a, b.asnumpy())
 
+@with_seed()
+def test_assign_a_row_to_ndarray():
+ """Test case from https://github.com/apache/incubator-mxnet/issues/9976"""
+ H, W = 10, 10
+ dtype = np.float32
+ a_np = np.random.random((H, W)).astype(dtype)
+ a_nd = mx.nd.array(a_np)
+
+ # assign directly
+ a_np[0] = a_np[1]
+ a_nd[0] = a_nd[1]
+ assert same(a_np, a_nd.asnumpy())
+
+ # assign a list
+ v = np.random.random(W).astype(dtype).tolist()
+ a_np[1] = v
+ a_nd[1] = v 
+ assert same(a_np, a_nd.asnumpy())
+
+ # assign a np.ndarray
+ v = np.random.random(W).astype(dtype)
+ a_np[2] = v
+ a_nd[2] = v 
+ assert same(a_np, a_nd.asnumpy())
+
+ # assign by slice 
+ a_np[0, :] = a_np[1]
+ a_nd[0, :] = a_nd[1]
+ assert same(a_np, a_nd.asnumpy())
 
 if __name__ == '__main__':
  import nose