Add an example that computes (non-persistent) homology.

git-svn-id: svn+ssh://scm.gforge.inria.fr/svnroot/gudhi/trunk@880 636b058d-ea47-450e-bf9e-a15bfbe3eedb

Former-commit-id: 21606fab3356681780ad446e73d5da56b29ec31d

2 files changed, 84 insertions, 0 deletions

diff --git a/src/Persistent_cohomology/example/CMakeLists.txt b/src/Persistent_cohomology/example/CMakeLists.txt
index ea69352e..50d10025 100644
--- a/src/Persistent_cohomology/example/CMakeLists.txt
+++ b/src/Persistent_cohomology/example/CMakeLists.txt
@@ -5,6 +5,10 @@ project(GUDHIExPersCohom)
 add_definitions( -DBOOST_ALL_NO_LIB )
 add_definitions( -DBOOST_ALL_DYN_LINK )
 
+add_executable(plain_homology plain_homology.cpp)
+target_link_libraries(plain_homology ${Boost_SYSTEM_LIBRARY})
+add_test(plain_homology ${CMAKE_CURRENT_BINARY_DIR}/plain_homology)
+
 add_executable(persistence_from_simple_simplex_tree persistence_from_simple_simplex_tree.cpp)
 target_link_libraries(persistence_from_simple_simplex_tree ${Boost_SYSTEM_LIBRARY})
 add_test(persistence_from_simple_simplex_tree ${CMAKE_CURRENT_BINARY_DIR}/persistence_from_simple_simplex_tree 1 0)
diff --git a/src/Persistent_cohomology/example/plain_homology.cpp b/src/Persistent_cohomology/example/plain_homology.cpp
new file mode 100644
index 00000000..e293e013
--- /dev/null
+++ b/src/Persistent_cohomology/example/plain_homology.cpp
@@ -0,0 +1,80 @@
+/*    This file is part of the Gudhi Library. The Gudhi library
+ *    (Geometric Understanding in Higher Dimensions) is a generic C++
+ *    library for computational topology.
+ *
+ *    Author(s):       Marc Glisse
+ *
+ *    Copyright (C) 2015  INRIA Saclay - Ile-de-France (France)
+ *
+ *    This program is free software: you can redistribute it and/or modify
+ *    it under the terms of the GNU General Public License as published by
+ *    the Free Software Foundation, either version 3 of the License, or
+ *    (at your option) any later version.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    GNU General Public License for more details.
+ *
+ *    You should have received a copy of the GNU General Public License
+ *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <gudhi/Simplex_tree.h>
+#include <gudhi/Persistent_cohomology.h>
+
+#include <iostream>
+
+using namespace Gudhi;
+
+struct MyOptions : Simplex_tree_options_full_featured {
+  // Implicitly use 0 as filtration value for all simplices
+  static const bool store_filtration = false;
+  // The persistence algorithm needs this
+  static const bool store_key = true;
+  // I have few vertices
+  typedef short Vertex_handle;
+};
+typedef Simplex_tree<MyOptions> ST;
+
+int main() {
+  ST st;
+
+  /* Complex to build. */
+  /*    1   3          */
+  /*    o---o          */
+  /*   /X\ /           */
+  /*  o---o   o        */
+  /*  2   0   4        */
+
+  const short triangle012[] = {0, 1, 2};
+  const short edge03[] = {0, 3};
+  const short edge13[] = {1, 3};
+  const short vertex4[] = {4};
+  st.insert_simplex_and_subfaces(triangle012);
+  st.insert_simplex_and_subfaces(edge03);
+  st.insert_simplex(edge13);
+  st.insert_simplex(vertex4);
+  // FIXME: Remove this line
+  st.set_dimension(2);
+
+  // Sort the simplices in the order of the filtration
+  st.initialize_filtration();
+
+  // Class for homology computation
+  persistent_cohomology::Persistent_cohomology<ST, persistent_cohomology::Field_Zp> pcoh(st);
+
+  // Initialize the coefficient field Z/2Z for homology
+  pcoh.init_coefficients(2);
+
+  // Compute the persistence diagram of the complex
+  pcoh.compute_persistent_cohomology();
+
+  // Print the result. The format is, on each line: 2 dim 0 inf
+  // where 2 represents the field, dim the dimension of the feature.
+  // 2  0 0 inf 
+  // 2  0 0 inf 
+  // 2  1 0 inf 
+  // means that in Z/2Z-homology, the Betti numbers are b0=2 and b1=1.
+  pcoh.output_diagram();
+}