* Clean up a little #if logic in MPI_WTICK / MPI_WTIME

* Update MPI_WTICK / MPI_WTIME man pages:
   * Fix C++ declarations
   * Note that we may use better than gettimeofday() on some platforms
 * Add "MPI_WTIME support" ("options:mpi-wtime") flag in ompi_info
   output indicating whether we use "native" or "gettimeofday" for
   MPI_WTIME

This commit was SVN r16774.

ompi/mpi/c/wtick.c

@@ -9,6 +9,7 @@
  *                         University of Stuttgart.  All rights reserved.
  * Copyright (c) 2004-2005 The Regents of the University of California.
  *                         All rights reserved.
+ * Copyright (c) 2007      Cisco Systems, Inc.  All rights reserved.
  * $COPYRIGHT$
  * 
  * Additional copyrights may follow
@@ -42,17 +43,16 @@ double MPI_Wtick(void)
     OPAL_CR_TEST_CHECKPOINT_READY();
 
 #if OPAL_TIMER_USEC_NATIVE
+    /* We may or may not have native usec precision on Windows, so put
+       this #if before the #ifdef checking for Windows. */
     return 0.000001;
-#else
-
-#if defined(__WINDOWS__)
+#elif defined(__WINDOWS__)
     if( (opal_timer_t)0 == opal_timer_base_get_freq() ) {
         opal_output( 0, "No timer frequency\n" );
     }
     return (double)opal_timer_base_get_freq();
 #else
+    /* Otherwise, we already return usec precision. */
     return 0.000001;
-#endif  /* defined(__WINDOWS__) */
-
-#endif  /* OPAL_TIMER_USEC_NATIVE */
+#endif
 }

ompi/mpi/c/wtime.c

@@ -44,20 +44,19 @@ double MPI_Wtime(void)
     double wtime;
 
 #if OPAL_TIMER_USEC_NATIVE
-    wtime = (double)opal_timer_base_get_usec() / 1000000.0;
-#else
-
-#if defined(__WINDOWS__)
-    wtime = ((double)opal_timer_base_get_cycles()) / ((double)opal_timer_base_get_freq());
-    return wtime;
+    /* We may or may not have native usec precision on Windows, so put
+       this #if before the #ifdef checking for Windows. */
+    wtime = ((double) opal_timer_base_get_usec()) / 1000000.0;
+#elif defined(__WINDOWS__)
+    wtime = ((double) opal_timer_base_get_cycles()) /
+        ((double) opal_timer_base_get_freq());
 #else
+    /* Fall back to gettimeofday() if we have nothing else */
     struct timeval tv;
     gettimeofday(&tv, NULL);
     wtime = tv.tv_sec;
     wtime += (double)tv.tv_usec / 1000000.0;
-#endif  /* defined(__WINDOWS__) */
-
-#endif  /* OPAL_TIMER_USEC_NATIVE */
+#endif
 
     OPAL_CR_TEST_CHECKPOINT_READY();
 

ompi/mpi/man/man3/MPI_Wtick.3

@@ -19,7 +19,7 @@ DOUBLE PRECISION MPI_WTICK()
 .SH C++ Syntax
 .nf
 #include <mpi.h>
-double Wtick()
+double MPI::Wtick()
 
 .SH RETURN VALUE
 .ft R
@@ -27,16 +27,22 @@ Time in seconds of resolution of MPI_Wtime.
 
 .SH DESCRIPTION
 .ft R
-MPI_Wtick returns the resolution of MPI_Wtime in seconds. That is, it returns, as a double-precision value, the number of seconds between successive clock ticks. For example, if the clock is implemented by the hardware as a counter that is incremented every millisecond, the value returned by MPI_Wtick should be 10^-3.
+MPI_Wtick returns the resolution of MPI_Wtime in seconds. That is, it
+returns, as a double-precision value, the number of seconds between
+successive clock ticks. For example, if the clock is implemented by
+the hardware as a counter that is incremented every millisecond, the
+value returned by MPI_Wtick should be 10^-3.
+.PP
+Note that on POSIX platforms, Open MPI should always return 10^-3 for
+MPI_Wtick.  The returned value may be different on Windows platforms.
 .PP
-.SH NOTE
-This function does not return an error value. Consequently, the result of calling it before MPI_Init or after MPI_Finalize is undefined.
 
+.SH NOTE
+This function does not return an error value. Consequently, the result
+of calling it before MPI_Init or after MPI_Finalize is undefined.
 
 .SH SEE ALSO 
 .ft R
 .sp
 MPI_Wtime
-
-
 ' @(#)MPI_Wtick.3 1.21 06/03/09   

ompi/mpi/man/man3/MPI_Wtime.3

@@ -19,7 +19,7 @@ DOUBLE PRECISION MPI_WTIME()
 .SH C++ Syntax
 .nf
 #include <mpi.h>
-double Wtime()
+double MPI::Wtime()
 
 .SH RETURN VALUE
 .ft R
@@ -48,7 +48,17 @@ The times returned are local to the node that called them. There is no requireme
 The boolean variable MPI_WTIME_IS_GLOBAL, a predefined attribute key that indicates whether clocks are synchronized, does not have a valid value in Open MPI, as the clocks are not guaranteed to be synchronized.
 
 .PP
-This is intended to be a high-resolution, elapsed (or wall) clock. See MPI_Wtick to determine the resolution of MPI_Wtime. 
+This function is intended to be a high-resolution, elapsed (or wall) clock. See MPI_Wtick to determine the resolution of MPI_Wtime. 
+.PP
+On POSIX platforms, this function may utilize a timer that is cheaper
+to invoke than the gettimeofday() system call, but will fall back to
+gettimeofday() if a cheap high-resolution timer is not available.  The
+ompi_info command can be consulted to see if Open MPI supports a
+native high-resolution timer on your platform; see the value for "MPI_WTIME 
+support" (or "options:mpi-wtime" when viewing the parsable
+output).  If this value is "native", a method that is likely to be
+cheaper than gettimeofday() will be used to obtain the time when
+MPI_Wtime is invoked.
 .PP
 This function does not return an error value. Consequently, the result of calling it before MPI_Init or after MPI_Finalize is undefined.
 

ompi/tools/ompi_info/param.cc

@@ -33,6 +33,7 @@
 #include <netdb.h>
 #endif
 
+#include MCA_timer_IMPLEMENTATION_HEADER
 #include "opal/mca/installdirs/installdirs.h"
 #include "opal/class/opal_value_array.h"
 #include "opal/util/printf.h"
@@ -353,6 +354,7 @@ void ompi_info::do_config(bool want_all)
                                         "yes" : "no");
   const string sparse_groups(OMPI_GROUP_SPARSE ? "yes" : "no");
   const string have_mpi_io(OMPI_PROVIDE_MPI_FILE_INTERFACE ? "yes" : "no");
+  const string wtime_support(OPAL_TIMER_USEC_NATIVE ? "native" : "gettimeofday");
 
   if (OMPI_HAVE_SOLARIS_THREADS || OMPI_HAVE_POSIX_THREADS) {
       threads = OMPI_HAVE_SOLARIS_THREADS ? "solaris" :
@@ -589,4 +591,5 @@ void ompi_info::do_config(bool want_all)
   out("mpirun default --prefix", "mpirun:prefix_by_default", 
       mpirun_prefix_by_default);
   out("MPI I/O support", "options:mpi-io", have_mpi_io);
+  out("MPI_WTIME support", "options:mpi-wtime", wtime_support);
 }