Implement "scattered Gustavson's," add testing, ensure works in ArmPL.

Author: BenBrock

include/spblas/vendor/armpl/detail/export_matrix_handle.hpp

@@ -0,0 +1,31 @@
+#pragma once
+
+#include <armpl_sparse.h>
+#include <spblas/detail/view_inspectors.hpp>
+
+namespace spblas {
+
+namespace __armpl {
+
+template <matrix M, typename O>
+  requires __detail::is_csr_view_v<M>
+void export_matrix_handle(operation_info_t& info, M&& m, armpl_spmat_t m_handle) {
+  auto nnz = info.result_nnz();
+  armpl_int_t m, n;
+  armpl_int_t *rowptr, *colind;
+  tensor_scalar_t<M>* values;
+  __armpl::export_spmat_csr<tensor_scalar_t<M>>(m_handle, 0, &m, &n, &rowptr,
+                                                &colind, &values);
+
+  std::copy(values, values + nnz, m.values().begin());
+  std::copy(colind, colind + nnz, m.colind().begin());
+  std::copy(rowptr, rowptr + m + 1, m.rowptr().begin());
+
+  free(values);
+  free(rowptr);
+  free(colind);
+}
+
+}
+
+}