Add ovnisync tool

Makefile

@@ -10,7 +10,7 @@ CFLAGS+=-g -O0
 #CFLAGS+=-fstack-protector-explicit
 #CFLAGS+=-flto
 
-BIN=dump test_speed ovni2prv emu libovni.so
+BIN=dump test_speed ovni2prv emu libovni.so ovnisync
 
 all: $(BIN)
 
@@ -28,5 +28,8 @@ libovni.so: ovni.o
 
 ovni2prv: ovni2prv.c ovni.o
 
+ovnisync: ovnisync.c
+	mpicc -lm $^ -o $@
+
 clean:
 	rm -f *.o $(BIN)

ovnisync.c

@@ -0,0 +1,155 @@
+#include <limits.h>
+#include <time.h>
+#include <stdio.h>
+#include <mpi.h>
+#include <stdlib.h>
+#include <math.h>
+#include <unistd.h>
+
+static double
+get_time()
+{
+	struct timespec tv;
+	if(clock_gettime(CLOCK_MONOTONIC, &tv) != 0)
+	{
+		perror("clock_gettime failed");
+		exit(EXIT_FAILURE);
+	}
+	return (double)(tv.tv_sec) * 1.0e-9 +
+		(double)tv.tv_nsec;
+}
+
+static int
+cmp_double(const void *pa, const void *pb)
+{
+	double a, b;
+
+	a = *(const double *) pa;
+	b = *(const double *) pb;
+
+	if(a < b)
+		return -1;
+	else if(a > b)
+		return 1;
+	else
+		return 0;
+}
+
+/* Called by rank 0 */
+static void
+get_offset(double *timetable, char (*hosttable)[HOST_NAME_MAX], int nproc, int nsamples)
+{
+	int i, j;
+	double median, mean, var, std;
+	double *offset;
+	double *delta;
+
+	offset = malloc(nproc * sizeof(double));
+	delta = malloc(nsamples * sizeof(double));
+
+	if(!offset || !delta)
+	{
+		perror("malloc");
+		exit(EXIT_FAILURE);
+	}
+
+	/* We use as ref the clock in rank 0 */
+
+	printf("%-10s %-20s %-20s %-20s\n", "rank", "hostname", "offset_median", "offset_std");
+	for(i=0; i<nproc; i++)
+	{
+		for(j=0; j<nsamples; j++)
+			delta[j] = timetable[j] - timetable[i*nsamples + j];
+
+		mean = 0.0;
+		var = 0.0;
+
+		qsort(delta, sizeof(*delta), nsamples, cmp_double);
+
+		median = delta[nsamples / 2];
+
+		for(j=0; j<nsamples; j++)
+		{
+			//printf("%f\n", delta[j]);
+			mean += delta[j];
+		}
+
+		mean /= nsamples;
+		for(j=0; j<nsamples; j++)
+		{
+			var += (delta[j] - mean) * (delta[j] - mean);
+		}
+		var /= (double) (nsamples - 1);
+		std = sqrt(var);
+		offset[i] = mean;
+		printf("%-10d %-20s %-20.0f %-20f\n", i, hosttable[i], median, std);
+	}
+
+	free(offset);
+	free(delta);
+}
+
+int
+main(int argc, char *argv[])
+{
+	double *t;
+	double *timetable;
+	int i, rank, nprocs, nsamples;
+	char (*hosttable)[HOST_NAME_MAX];
+
+	MPI_Init(&argc, &argv);
+
+	if(!argv[1])
+		nsamples = 100;
+	else
+		nsamples = atoi(argv[1]);
+
+	MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+	MPI_Comm_size(MPI_COMM_WORLD, &nprocs);
+
+	timetable = calloc(nsamples * nprocs, sizeof(double));
+	hosttable = calloc(nprocs, sizeof(*hosttable));
+	t = calloc(nsamples, sizeof(double));
+
+	if(!timetable || !t || !hosttable)
+	{
+		perror("calloc");
+		exit(EXIT_FAILURE);
+	}
+
+	/* Warm up iterations */
+	for(i=0; i<20; i++)
+	{
+		MPI_Barrier(MPI_COMM_WORLD);
+		get_time();
+	}
+
+	for(i=0; i<nsamples; i++)
+	{
+		MPI_Barrier(MPI_COMM_WORLD);
+		t[i] = get_time();
+	}
+
+	if(gethostname(hosttable[rank], HOST_NAME_MAX) != 0)
+	{
+		perror("gethostname");
+		exit(EXIT_FAILURE);
+	}
+
+	MPI_Gather(hosttable[rank], sizeof(*hosttable), MPI_CHAR,
+		hosttable[0], sizeof(*hosttable), MPI_CHAR,
+		0, MPI_COMM_WORLD);
+
+	MPI_Gather(t, nsamples, MPI_DOUBLE,
+		timetable, nsamples, MPI_DOUBLE,
+		0, MPI_COMM_WORLD);
+
+	if(rank == 0)
+		get_offset(timetable, hosttable, nprocs, nsamples);
+
+	free(hosttable);
+	free(timetable);
+	free(t);
+	MPI_Finalize();
+	return 0;
+}