Uses pkg-config when configuring google sparse hash.

In case google sparsehash uses a non-standard prefix, e.g., in Homebrew.

configure.ac

@@ -319,11 +319,17 @@ fi
 
 dnl sparsehash
 if test "$USING_SPARSEHASH" = "yes"; then
-   [CPPFLAGS="${CPPFLAGS} -I/usr/include/sparsehash -I/usr/include/google"]
-   AC_CHECK_HEADER([dense_hash_set],
-	           [],
+   PKG_CHECK_MODULES(SPARSEHASH, [libsparsehash], AC_DEFINE([HAVE_SPARSEHASH], [1],
+                     [Using google's sparsehash]), [])
+   AC_SUBST(SPARSEHASH_CFLAGS)
+   [OLD_CXXFLAGS="${CXXFLAGS}"]
+   [OLD_CPPFLAGS="${CPPFLAGS}"]
+   [CXXFLAGS="${CXXFLAGS} ${SPARSEHASH_CFLAGS}"]
+   [CPPFLAGS="${CPPFLAGS} ${SPARSEHASH_CFLAGS}"]
+   AC_CHECK_HEADER([sparsehash/dense_hash_set], [],
                    [AC_MSG_ERROR([sparsehash headers not found])])
-   AC_DEFINE_UNQUOTED([HAVE_SPARSEHASH],"1", [Using google's sparsehash])
+   [CXXFLAGS="${OLD_CXXFLAGS}"]
+   [CPPFLAGS="${OLD_CPPFLAGS}"]
 fi
 
 dnl Checks for typedefs, structures, and compiler characteristics.

src/graph/clustering/graph_clustering.hh

@@ -24,7 +24,7 @@
 #include <boost/mpl/if.hpp>
 
 #ifdef HAVE_SPARSEHASH
-#include <dense_hash_set>
+#include <sparsehash/dense_hash_set>
 #endif
 
 #ifndef __clang__

src/graph/community/graph_blockmodel.hh

@@ -28,8 +28,8 @@
 #include <tuple>
 
 #ifdef HAVE_SPARSEHASH
-#include <dense_hash_set>
-#include <dense_hash_map>
+#include <sparsehash/dense_hash_set>
+#include <sparsehash/dense_hash_map>
 #endif
 
 #include "../generation/sampler.hh"

src/graph/community/graph_community_network.hh

@@ -21,7 +21,7 @@
 #include <unordered_map>
 
 #ifdef HAVE_SPARSEHASH
-#include <dense_hash_map>
+#include <sparsehash/dense_hash_map>
 #endif
 
 #include <iostream>

src/graph/stats/graph_parallel.hh

@@ -19,7 +19,7 @@
 #include <unordered_map>
 
 #ifdef HAVE_SPARSEHASH
-#include <dense_hash_map>
+#include <sparsehash/dense_hash_map>
 #endif
 
 #include "graph_util.hh"