eigen-allocator: refactor check of pyArray memory layout vs desired output layout

eigen-allocator: try a fix for mutable Eigen::Ref from Python array with "wrong" layout

* trick transposes pyArray to get the right layout :)

include/eigenpy/eigen-allocator.hpp

@@ -232,6 +232,22 @@ struct EigenAllocator {
 };
 
 #if EIGEN_VERSION_AT_LEAST(3, 2, 0)
+/// @brief Check if we need to allocate @tparam MatType to convert @param
+/// pyArray.
+/// @details do not allocate if:
+/// want row-major & data C-contiguous OR
+/// want col-major & data F-contiguous OR
+/// you want a compile-time vector
+/// in these cases, data layout fits desired view layout
+template <typename MatType>
+inline bool is_arr_layout_compatible_with_mat_type(PyArrayObject *pyArray) {
+  bool is_array_C_cont = PyArray_IS_C_CONTIGUOUS(pyArray);
+  bool is_array_F_cont = PyArray_IS_F_CONTIGUOUS(pyArray);
+  return (MatType::IsRowMajor && is_array_C_cont) ||
+         (!MatType::IsRowMajor && is_array_F_cont) ||
+         MatType::IsVectorAtCompileTime;
+}
+
 template <typename MatType, int Options, typename Stride>
 struct EigenAllocator<Eigen::Ref<MatType, Options, Stride> > {
   typedef Eigen::Ref<MatType, Options, Stride> RefType;
@@ -255,14 +271,8 @@ struct EigenAllocator<Eigen::Ref<MatType, Options, Stride> > {
     const int pyArray_type_code = EIGENPY_GET_PY_ARRAY_TYPE(pyArray);
     const int Scalar_type_code = Register::getTypeCode<Scalar>();
     if (pyArray_type_code != Scalar_type_code) need_to_allocate |= true;
-    if ((MatType::IsRowMajor && (PyArray_IS_C_CONTIGUOUS(pyArray) &&
-                                 !PyArray_IS_F_CONTIGUOUS(pyArray))) ||
-        (!MatType::IsRowMajor && (PyArray_IS_F_CONTIGUOUS(pyArray) &&
-                                  !PyArray_IS_C_CONTIGUOUS(pyArray))) ||
-        MatType::IsVectorAtCompileTime ||
-        (PyArray_IS_F_CONTIGUOUS(pyArray) &&
-         PyArray_IS_C_CONTIGUOUS(pyArray)))  // no need to allocate
-      need_to_allocate |= false;
+    if (is_arr_layout_compatible_with_mat_type<MatType>(pyArray))
+      need_to_allocate |= false;  // no need to allocate
     else
       need_to_allocate |= true;
     if (Options !=
@@ -276,6 +286,10 @@ struct EigenAllocator<Eigen::Ref<MatType, Options, Stride> > {
 
     void *raw_ptr = storage->storage.bytes;
     if (need_to_allocate) {
+      PyObject *pyarr_transposed = PyArray_Transpose(pyArray, NULL);
+      allocate((PyArrayObject *)pyarr_transposed, storage);
+      /*
+      std::cout << "  doing allocate\n";
       MatType *mat_ptr;
       mat_ptr = details::init_matrix_or_array<MatType>::run(pyArray);
       RefType mat_ref(*mat_ptr);
@@ -326,6 +340,7 @@ struct EigenAllocator<Eigen::Ref<MatType, Options, Stride> > {
           throw Exception(
               "You asked for a conversion which is not implemented.");
       }
+      */
     } else {
       assert(pyArray_type_code == Scalar_type_code);
       typename NumpyMap<MatType, Scalar, Options, NumpyMapStride>::EigenMap
@@ -365,14 +380,8 @@ struct EigenAllocator<const Eigen::Ref<const MatType, Options, Stride> > {
     const int Scalar_type_code = Register::getTypeCode<Scalar>();
 
     if (pyArray_type_code != Scalar_type_code) need_to_allocate |= true;
-    if ((MatType::IsRowMajor && (PyArray_IS_C_CONTIGUOUS(pyArray) &&
-                                 !PyArray_IS_F_CONTIGUOUS(pyArray))) ||
-        (!MatType::IsRowMajor && (PyArray_IS_F_CONTIGUOUS(pyArray) &&
-                                  !PyArray_IS_C_CONTIGUOUS(pyArray))) ||
-        MatType::IsVectorAtCompileTime ||
-        (PyArray_IS_F_CONTIGUOUS(pyArray) &&
-         PyArray_IS_C_CONTIGUOUS(pyArray)))  // no need to allocate
-      need_to_allocate |= false;
+    if (is_arr_layout_compatible_with_mat_type<MatType>(pyArray))
+      need_to_allocate |= false;  // no need to allocate
     else
       need_to_allocate |= true;
     if (Options !=

unittest/python/test_std_vector.py

@@ -76,9 +76,10 @@ print("-----------------")
 print("l3:")
 vector.setZero(l3)
 pprint.pp(list(l3))
-# checkZero(l3)
+checkZero(l3)
 print("-----------------")
 
 print("l4:")
 vector.setZero(l4)
 pprint.pp(list(l4))
+checkZero(l4)