Add parameter checks to BFS and SSSP in C API (#2844)

MG testing resulted in discovering an assumption in the C API about types that needs to be validated.  Added checks to BFS and SSSP so that the type checks will be done right away before trying to interpret the data incorrectly.

Won't pass until #2847 is addressed

Authors:
  - Chuck Hastings (https://github.com/ChuckHastings)

Approvers:
  - Seunghwa Kang (https://github.com/seunghwak)
  - Joseph Nke (https://github.com/jnke2016)
  - Rick Ratzel (https://github.com/rlratzel)

URL: #2844

cpp/src/c_api/bfs.cpp

@@ -194,6 +194,14 @@ extern "C" cugraph_error_code_t cugraph_bfs(const cugraph_resource_handle_t* han
                                             cugraph_paths_result_t** result,
                                             cugraph_error_t** error)
 {
+  CAPI_EXPECTS(
+    reinterpret_cast<cugraph::c_api::cugraph_graph_t*>(graph)->vertex_type_ ==
+      reinterpret_cast<cugraph::c_api::cugraph_type_erased_device_array_view_t const*>(sources)
+        ->type_,
+    CUGRAPH_INVALID_INPUT,
+    "vertex type of graph and sources must match",
+    *error);
+
   cugraph::c_api::bfs_functor functor(handle,
                                       graph,
                                       sources,

cpp/tests/c_api/bfs_test.c

@@ -116,6 +116,58 @@ int generic_bfs_test(vertex_t* h_src,
   return test_ret_value;
 }
 
+int test_bfs_exceptions()
+{
+  size_t num_edges    = 8;
+  size_t num_vertices = 6;
+  size_t depth_limit  = 1;
+  size_t num_seeds    = 1;
+
+  vertex_t src[]   = {0, 1, 1, 2, 2, 2, 3, 4};
+  vertex_t dst[]   = {1, 3, 4, 0, 1, 3, 5, 5};
+  weight_t wgt[]   = {0.1f, 2.1f, 1.1f, 5.1f, 3.1f, 4.1f, 7.2f, 3.2f};
+  int64_t seeds[] = {0};
+
+  int test_ret_value = 0;
+
+  cugraph_error_code_t ret_code = CUGRAPH_SUCCESS;
+  cugraph_error_t* ret_error    = NULL;
+
+  cugraph_resource_handle_t* p_handle                    = NULL;
+  cugraph_graph_t* p_graph                               = NULL;
+  cugraph_paths_result_t* p_result                       = NULL;
+  cugraph_type_erased_device_array_t* p_sources          = NULL;
+  cugraph_type_erased_device_array_view_t* p_source_view = NULL;
+
+  p_handle = cugraph_create_resource_handle(NULL);
+  TEST_ASSERT(test_ret_value, p_handle != NULL, "resource handle creation failed.");
+
+  ret_code = create_test_graph(
+    p_handle, src, dst, wgt, num_edges, FALSE, FALSE, FALSE, &p_graph, &ret_error);
+
+  /*
+   * FIXME: in create_graph_test.c, variables are defined but then hard-coded to
+   * the constant INT32. It would be better to pass the types into the functions
+   * in both cases so that the test cases could be parameterized in the main.
+   */
+  ret_code =
+    cugraph_type_erased_device_array_create(p_handle, num_seeds, INT64, &p_sources, &ret_error);
+  TEST_ASSERT(test_ret_value, ret_code == CUGRAPH_SUCCESS, "p_sources create failed.");
+
+  p_source_view = cugraph_type_erased_device_array_view(p_sources);
+
+  ret_code = cugraph_type_erased_device_array_view_copy_from_host(
+    p_handle, p_source_view, (byte_t*)seeds, &ret_error);
+  TEST_ASSERT(test_ret_value, ret_code == CUGRAPH_SUCCESS, "src copy_from_host failed.");
+
+  ret_code = cugraph_bfs(
+    p_handle, p_graph, p_source_view, FALSE, depth_limit, TRUE, FALSE, &p_result, &ret_error);
+
+  TEST_ASSERT(test_ret_value, ret_code == CUGRAPH_INVALID_INPUT, "cugraph_bfs expected to fail");
+
+  return test_ret_value;
+}
+
 int test_bfs()
 {
   size_t num_edges    = 8;
@@ -176,5 +228,6 @@ int main(int argc, char** argv)
   int result = 0;
   result |= RUN_TEST(test_bfs);
   result |= RUN_TEST(test_bfs_with_transpose);
+  result |= RUN_TEST(test_bfs_exceptions);
   return result;
 }

python/cugraph/cugraph/traversal/bfs.py

@@ -55,7 +55,10 @@ def _ensure_args(G, start, i_start, directed):
         else:
             if not isinstance(start, cudf.DataFrame):
                 if not isinstance(start, dask_cudf.DataFrame):
-                    start = cudf.DataFrame({"starts": cudf.Series(start)})
+                    vertex_dtype = G.nodes().dtype
+                    start = cudf.DataFrame(
+                        {"starts": cudf.Series(start, dtype=vertex_dtype)}
+                    )
 
             if G.is_renumbered():
                 validlen = len(
@@ -224,7 +227,8 @@ def bfs(
         if is_dataframe:
             start = start[start.columns[0]]
         else:
-            start = cudf.Series(start, name="starts")
+            vertex_dtype = G.nodes().dtype
+            start = cudf.Series(start, dtype=vertex_dtype)
 
     distances, predecessors, vertices = pylibcugraph_bfs(
         handle=ResourceHandle(),