Add example code for Gray order

examples/CMakeLists.txt

@@ -16,6 +16,7 @@ if(NOT ${_HEADER_ONLY} OR NOT ${USE_CUDA})
   add_subdirectory(degree_order)
   add_subdirectory(custom_order)
   add_subdirectory(format_conversion)
+  add_subdirectory(gray_order)
   add_subdirectory(rcm_order)
   add_subdirectory(sparse_feature)
   add_subdirectory(sparse_reader)

examples/gray_order/CMakeLists.txt

@@ -0,0 +1,2 @@
+add_executable(gray_order ${CMAKE_CURRENT_SOURCE_DIR}/gray_order.cc)
+target_link_libraries(gray_order sparsebase)

examples/gray_order/gray_order.cc

@@ -0,0 +1,88 @@
+#include <iostream>
+#include <set>
+
+#include "sparsebase/bases/iobase.h"
+#include "sparsebase/bases/reorder_base.h"
+#include "sparsebase/format/csr.h"
+#include "sparsebase/format/format_order_one.h"
+#include "sparsebase/format/format_order_two.h"
+#include "sparsebase/object/object.h"
+#include "sparsebase/reorder/gray_reorder.h"
+
+using namespace std;
+using namespace sparsebase;
+using namespace io;
+using namespace bases;
+using namespace format;
+using namespace reorder;
+
+using vertex_type = int;
+using edge_type = int;
+using value_type = float;
+
+int main(int argc, char *argv[]) {
+  if (argc < 2) {
+    cout << "Usage: ./gray_order <matrix_market_file>\n";
+    cout
+        << "Hint: You can use the edgelist: examples/data/com-dblp.mtx\n";
+    return 1;
+  }
+  cout << "F t re  s sp r e!" << endl;
+  string file_name = argv[1];
+
+  cout << "********************************" << endl;
+
+  cout << "Reading graph from " << file_name << "..." << endl;
+  auto csr =
+      sparsebase::bases::IOBase::ReadMTXToCSR<vertex_type, edge_type,
+          value_type>(file_name, true);
+  cout << "Number of vertices: " << csr->get_dimensions()[0] << endl;
+  cout << "Number of edges: " << csr->get_num_nnz() << endl;
+
+  vertex_type num_rows = csr->get_dimensions()[0];
+  edge_type num_non_zeros = csr->get_num_nnz();
+
+  cout << "********************************" << endl;
+  cout << "Generating Gray ordering..." << endl;
+
+  // A context representing the host system
+  context::CPUContext cpu_context;
+
+  // Create a parameters object to store special parameters specific
+  GrayReorderParams gray_params(
+      BitMapSize::BitSize16, 20,
+      ((num_non_zeros / num_rows) / BitMapSize::BitSize16));
+
+  vertex_type *gray_reorder = bases::ReorderBase::Reorder<GrayReorder>(
+      gray_params, csr, {&cpu_context}, true);
+  cout << "********************************" << endl;
+
+  cout << "Checking the correctness of the ordering..." << endl;
+  bool order_is_correct = true;
+  set<vertex_type> ids;
+  for (vertex_type i = 0; i < num_rows && order_is_correct; i++) {
+    vertex_type i_order = gray_reorder[i];
+    if (i_order < num_rows && ids.find(i_order) == ids.end()) {
+      ids.insert(i_order);
+    } else {
+      cout << "Gray ordering is incorrect!";
+      order_is_correct = false;
+      return 1;
+    }
+  }
+  if (ids.size() > num_rows) {
+    cout << "Gray ordering is incorrect!";
+    order_is_correct = false;
+  }
+  if (order_is_correct) {
+    cout << "Order is correct!" << endl;
+  } else {
+    cout << "Gray ordering is incorrect!";
+    order_is_correct = false;
+    return 1;
+  }
+
+  delete gray_reorder;
+
+  return 0;
+}