restore old version of MPI_Wtime(). we're not using it anyway.

src/STUBS/mpi.cpp

@@ -17,11 +17,11 @@
 
 #include "../version.h"
 
-#include <chrono>
-#include <cstdint>
-#include <cstdio>
-#include <cstdlib>
-#include <cstring>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/time.h>
 
 /* data structure for double/int */
 
@@ -164,10 +164,23 @@ int MPI_Finalize()
 }
 
 /* ---------------------------------------------------------------------- */
-static auto initial_time = std::chrono::steady_clock::now();
+
 double MPI_Wtime()
 {
-  return std::chrono::duration<double>(std::chrono::steady_clock::now() - initial_time).count();
+#if defined(_MSC_VER)
+  double t;
+
+  t = GetTickCount();
+  t /= 1000.0;
+  return t;
+#else
+  double time;
+  struct timeval tv;
+
+  gettimeofday(&tv, NULL);
+  time = 1.0 * tv.tv_sec + 1.0e-6 * tv.tv_usec;
+  return time;
+#endif
 }
 
 /* ---------------------------------------------------------------------- */