Index: boost/mpi/environment.hpp
===================================================================
--- boost/mpi/environment.hpp	(revision 82512)
+++ boost/mpi/environment.hpp	(working copy)
@@ -25,9 +25,17 @@
  *  The @c environment class is used to initialize, finalize, and
  *  query the MPI environment. It will typically be used in the @c
  *  main() function of a program, which will create a single instance
- *  of @c environment initialized with the arguments passed to the
- *  program:
+ *  of @c environment:
+ *  @code
+ *  int main(int argc, char* argv[])
+ *  {
+ *    mpi::environment env;
+ *  }
+ *  @endcode
  *
+ *  Some implementations requires the environement to be initialized 
+ *  with the arguments passed to the program:
+ *
  *  @code
  *  int main(int argc, char* argv[])
  *  {
@@ -41,9 +49,11 @@
  *  uncaught exception) in its destructor.
  *
  *  The use of @c environment is not mandatory. Users may choose to
- *  invoke @c MPI_Init and @c MPI_Finalize manually. In this case, no
- *  @c environment object is needed. If one is created, however, it
- *  will do nothing on either construction or destruction.
+ *  invoke @c MPI_Init (or @c MPI_Thread_init and @c MPI_Finalize 
+ *  manually.
+ *  In this case, no @c environment object is needed.
+ *  If one is created, however, it will do nothing on either
+ *  onstruction or destruction.
  */
 class BOOST_MPI_DECL environment : noncopyable {
 public:
Index: boost/mpi/config.hpp
===================================================================
--- boost/mpi/config.hpp	(revision 82512)
+++ boost/mpi/config.hpp	(working copy)
@@ -23,7 +23,7 @@
 /** @brief Define this macro to avoid expensice MPI_Pack/Unpack calls on 
  *  homogeneous machines.
 */
-//#define BOOST_MPI_HOMOGENEOUS
+#define BOOST_MPI_HOMOGENEOUS
 
 // If this is an MPI-2 implementation, define configuration macros for
 // the features we are interested in.
@@ -48,6 +48,11 @@
  *  environment class will provide a default constructor. This macro is 
  *  always defined for MPI-2 implementations. */
 #  define BOOST_MPI_HAS_NOARG_INITIALIZATION
+#else
+// If this is an MPI-1.x implementation, no arg initialization for
+// mpi environement could still be available, but not mandatory.
+// Undef this if no arg init is available:
+//#  define BOOST_MPI_HAS_NOARG_INITIALIZATION
 #endif
 
 #if defined(MPIAPI)