[la.container.matrix-view] add axpy variant

dune/xt/la/container/matrix-view.hh

@@ -374,6 +374,27 @@ public:
         add_to_entry(ii, jj, xx.get_entry(ii, jj) * alpha);
   }
 
+  template <class OtherTraits>
+  inline void axpy(const ScalarType& alpha, const MatrixInterface<OtherTraits, ScalarType>& xx)
+  {
+    const auto& patt = get_pattern();
+#ifndef NDEBUG
+    const auto& other_patt = xx.pattern();
+    if (xx.rows() != rows() || xx.cols() != cols())
+      DUNE_THROW(Common::Exceptions::shapes_do_not_match, "Shapes do not match!");
+    for (size_t ii = 0; ii < rows(); ++ii)
+      for (auto&& jj : other_patt.inner(ii)) {
+        // The EigenRowMajorSparseMatrix automatically adds one entry to an empty row
+        if (!patt.contains(ii, jj)
+            && !(patt.inner(ii).size() == 0 && other_patt.inner(ii).size() == 1 && other_patt.inner(ii)[0] == 0))
+          DUNE_THROW(Dune::MathError, "Pattern of xx has to be a subset of this pattern!");
+      }
+#endif
+    for (size_t ii = 0; ii < rows(); ++ii)
+      for (auto&& jj : patt.inner(ii))
+        add_to_entry(ii, jj, xx.get_entry(ii, jj) * alpha);
+  }
+
   template <class XX, class YY>
   inline void mv(const XX& xx, YY& yy) const
   {

dune/xt/test/la/matrix_and_vector_view.tpl

@@ -207,6 +207,10 @@ struct MatrixViewTest_{{T_NAME}} : public ::testing::Test
     // test axpy
     view_upperleft.axpy(ScalarType(4), view_upperleft);
     sparse_view_upperleft.axpy(ScalarType(4), sparse_view_upperleft);
+    sparse_view_lowerright.axpy(ScalarType(4), sparse_lowerright_saved);
+    EXPECT_DOUBLE_OR_COMPLEX_EQ(ScalarType(5)*sparse_lowerright_saved.get_entry(0, 0), sparse_view_lowerright.get_entry(0, 0));
+    EXPECT_DOUBLE_OR_COMPLEX_EQ(ScalarType(5)*sparse_lowerright_saved.get_entry(1, 0), sparse_view_lowerright.get_entry(1, 0));
+    sparse_view_lowerright.scal(ScalarType(1./5.));
     VectorImp test_vec(2, ScalarType(1.));
     vec_view.axpy(-1., test_vec);
     EXPECT_DOUBLE_OR_COMPLEX_EQ(ScalarType(0), vec_view.get_entry(0));