From 12d8432ca8e4005ea36a0ffa4437299bf8748c96 Mon Sep 17 00:00:00 2001
From: Wolfgang Bangerth <bangerth@colostate.edu>
Date: Tue, 20 Mar 2018 17:06:50 -0600
Subject: [PATCH] Add a test.

---
 .../sparsity_pattern_full_matrix_01.cc        | 62 +++++++++++++++++++
 .../sparsity_pattern_full_matrix_01.output    |  4 ++
 2 files changed, 66 insertions(+)
 create mode 100644 tests/sparsity/sparsity_pattern_full_matrix_01.cc
 create mode 100644 tests/sparsity/sparsity_pattern_full_matrix_01.output

diff --git a/tests/sparsity/sparsity_pattern_full_matrix_01.cc b/tests/sparsity/sparsity_pattern_full_matrix_01.cc
new file mode 100644
index 0000000000..be189878a8
--- /dev/null
+++ b/tests/sparsity/sparsity_pattern_full_matrix_01.cc
@@ -0,0 +1,62 @@
+
+// ---------------------------------------------------------------------
+//
+// Copyright (C) 2004 - 2017 by the deal.II authors
+//
+// This file is part of the deal.II library.
+//
+// The deal.II library is free software; you can use it, redistribute
+// it, and/or modify it under the terms of the GNU Lesser General
+// Public License as published by the Free Software Foundation; either
+// version 2.1 of the License, or (at your option) any later version.
+// The full text of the license can be found in the file LICENSE at
+// the top level of the deal.II distribution.
+//
+// ---------------------------------------------------------------------
+
+
+
+// Check SparsityPattern::copy_from(FullMatrix). This function took
+// extraordinary amounts of CPU time: for a 1 x 400,000 matrix, it
+// took around 50 seconds; after the patch that fixed the quadratic
+// behavior, it takes less than one second
+//
+// To make sure we really catch the old bevahior through the test
+// suite time out, we also do a matrix of size 1 x 4,000,000, which
+// would have taken more than an hour before and now still takes less
+// than one second. Finally, also try a square matrix because this
+// case is treated specially in the function.
+
+#include "../tests.h"
+#include <deal.II/lac/sparsity_pattern.h>
+#include <deal.II/lac/full_matrix.h>
+
+
+void test (const unsigned int M,
+           const unsigned int N)
+{
+  SparsityPattern sp (M,N);
+
+  // fill a full matrix completely
+  FullMatrix<double> mat(M,N);
+  for (unsigned int m=0; m<M; ++m)
+    for (unsigned int n=0; n<N; ++n)
+      mat(m,n) = 1;
+
+  // then copy the nonzero entries of 'mat' (i.e., all entries) to the
+  // sparsity pattern
+  sp.copy_from (mat);
+
+  deallog << sp.n_nonzero_elements() << std::endl;
+}
+
+
+
+int main ()
+{
+  initlog();
+
+  test (1, 400000);
+  test (1, 4000000);
+  test (10, 10);
+}
diff --git a/tests/sparsity/sparsity_pattern_full_matrix_01.output b/tests/sparsity/sparsity_pattern_full_matrix_01.output
new file mode 100644
index 0000000000..a24b221cb6
--- /dev/null
+++ b/tests/sparsity/sparsity_pattern_full_matrix_01.output
@@ -0,0 +1,4 @@
+
+DEAL::400000
+DEAL::4000000
+DEAL::100
-- 
2.39.5