Modify googlehash use to account for namespace issues.

The namespace declaration for googlehash is a configurable macro that
can be disabled.  In particular, it is disabled within google, causing
compile errors since `dense_hash_map`/`sparse_hash_map` are then in
the global namespace instead of in `::google`.

Here we play a bit of gynastics to allow for both `google::*_hash_map`
and `*_hash_map`, while limiting namespace polution.  Symbols within
the `::google` namespace are imported into `Eigen::google`.

We also remove checks based on `_SPARSE_HASH_MAP_H_`, as this is
fragile, and instead require `EIGEN_GOOGLEHASH_SUPPORT` to be
defined.

bench/sparse_randomsetter.cpp

@@ -1,6 +1,7 @@
 
 #define NOGMM
 #define NOMTL
+#define EIGEN_GOOGLEHASH_SUPPORT 1
 
 #include <map>
 #include <ext/hash_map>

test/sparse.h

@@ -29,10 +29,6 @@
 
 #endif
 
-#ifdef EIGEN_GOOGLEHASH_SUPPORT
-  #include <google/sparse_hash_map>
-#endif
-
 #include <Eigen/Cholesky>
 #include <Eigen/LU>
 #include <Eigen/Sparse>

unsupported/Eigen/SparseExtra

@@ -24,6 +24,7 @@
 
 #ifdef EIGEN_GOOGLEHASH_SUPPORT
   #include <google/dense_hash_map>
+  #include <google/sparse_hash_map>
 #endif
 
 /**

unsupported/Eigen/src/SparseExtra/RandomSetter.h

@@ -10,6 +10,12 @@
 #ifndef EIGEN_RANDOMSETTER_H
 #define EIGEN_RANDOMSETTER_H
 
+#if defined(EIGEN_GOOGLEHASH_SUPPORT)
+// Ensure the ::google namespace exists, required for checking existence of 
+// ::google::dense_hash_map and ::google::sparse_hash_map.
+namespace google {}
+#endif
+
 namespace Eigen {
 
 /** Represents a std::map
@@ -56,7 +62,26 @@ template<typename Scalar> struct StdUnorderedMapTraits
 };
 #endif // EIGEN_UNORDERED_MAP_SUPPORT
 
-#ifdef _DENSE_HASH_MAP_H_
+#if defined(EIGEN_GOOGLEHASH_SUPPORT)
+
+namespace google {
+  
+// Namespace work-around, since sometimes dense_hash_map and sparse_hash_map
+// are in the global namespace, and other times they are under ::google.
+using namespace ::google;
+
+template<typename KeyType, typename Scalar>
+struct DenseHashMap {
+  typedef dense_hash_map<KeyType, Scalar> type;
+};
+
+template<typename KeyType, typename Scalar>
+struct SparseHashMap {
+  typedef sparse_hash_map<KeyType, Scalar> type;
+};
+
+} // namespace google
+
 /** Represents a google::dense_hash_map
   *
   * \see RandomSetter
@@ -64,7 +89,7 @@ template<typename Scalar> struct StdUnorderedMapTraits
 template<typename Scalar> struct GoogleDenseHashMapTraits
 {
   typedef int KeyType;
-  typedef google::dense_hash_map<KeyType,Scalar> Type;
+  typedef typename google::DenseHashMap<KeyType,Scalar>::type Type;
   enum {
     IsSorted = 0
   };
@@ -72,9 +97,7 @@ template<typename Scalar> struct GoogleDenseHashMapTraits
   static void setInvalidKey(Type& map, const KeyType& k)
   { map.set_empty_key(k); }
 };
-#endif
 
-#ifdef _SPARSE_HASH_MAP_H_
 /** Represents a google::sparse_hash_map
   *
   * \see RandomSetter
@@ -82,7 +105,7 @@ template<typename Scalar> struct GoogleDenseHashMapTraits
 template<typename Scalar> struct GoogleSparseHashMapTraits
 {
   typedef int KeyType;
-  typedef google::sparse_hash_map<KeyType,Scalar> Type;
+  typedef typename google::SparseHashMap<KeyType,Scalar>::type Type;
   enum {
     IsSorted = 0
   };
@@ -134,18 +157,17 @@ template<typename Scalar> struct GoogleSparseHashMapTraits
   * GoogleSparseHashMapTraits, GnuHashMapTraits, and finally StdMapTraits.
   *
   * For performance and memory consumption reasons it is highly recommended to use one of
-  * the Google's hash_map implementation. To enable the support for them, you have two options:
-  *  - \#include <google/dense_hash_map> yourself \b before Eigen/Sparse header
-  *  - define EIGEN_GOOGLEHASH_SUPPORT
-  * In the later case the inclusion of <google/dense_hash_map> is made for you.
+  * Google's hash_map implementations. To enable the support for them, you must define
+  * EIGEN_GOOGLEHASH_SUPPORT. This will include both <google/dense_hash_map> and
+  * <google/sparse_hash_map> for you.
   *
-  * \see http://code.google.com/p/google-sparsehash/
+  * \see https://github.com/sparsehash/sparsehash
   */
 template<typename SparseMatrixType,
          template <typename T> class MapTraits =
-#if defined _DENSE_HASH_MAP_H_
+#if defined(EIGEN_GOOGLEHASH_SUPPORT)
           GoogleDenseHashMapTraits
-#elif defined _HASH_MAP
+#elif defined(_HASH_MAP)
           GnuHashMapTraits
 #else
           StdMapTraits

unsupported/test/sparse_extra.cpp

@@ -123,10 +123,8 @@ template<typename SparseMatrixType> void sparse_extra(const SparseMatrixType& re
     #ifdef EIGEN_UNORDERED_MAP_SUPPORT
     VERIFY(( test_random_setter<RandomSetter<SparseMatrixType, StdUnorderedMapTraits> >(m,refMat,nonzeroCoords) ));
     #endif
-    #ifdef _DENSE_HASH_MAP_H_
+    #ifdef EIGEN_GOOGLEHASH_SUPPORT
     VERIFY(( test_random_setter<RandomSetter<SparseMatrixType, GoogleDenseHashMapTraits> >(m,refMat,nonzeroCoords) ));
-    #endif
-    #ifdef _SPARSE_HASH_MAP_H_
     VERIFY(( test_random_setter<RandomSetter<SparseMatrixType, GoogleSparseHashMapTraits> >(m,refMat,nonzeroCoords) ));
     #endif