Ring communication

exercise_06/nbcomm/Makefile

+CFLAGS = -O3 -march=native -Wall -std=c99
+LDFLAGS = -lm
+SOURCES = $(wildcard *.c)
+
+TARGETS =
+TARGETS := $(patsubst %.c,%.run,$(SOURCES)) $(TARGETS)
+
+DEPS = $(wildcard *.h)
+CC = mpicc
+
+all : $(TARGETS)
+
+time : $(patsubst %.run,%.time,$(TARGETS))
+
+%.run : %.c $(DEPS)
+	$(CC) $(CFLAGS) -DSCHEDULE=static -o $@ $< $(LDFLAGS)
+
+%.time : %.run
+	@echo $<
+	@time -f "\t%e real" ./$< > /dev/null
+
+clean :
+	rm -f *.o
+	rm -f *.run

exercise_06/nbcomm/nbcomm.c

+#include <mpi.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <string.h>
+#include <stdlib.h>
+
+
+#define DEFAULT_COMM MPI_COMM_WORLD
+
+#define EAGER_PROTO 1
+
+#if EAGER_PROTO
+// using rendez-vous protocol
+#define SEND MPI_Issend
+#define RECV MPI_Recv
+#else
+// defaults
+#define SEND MPI_Ssend
+#define RECV MPI_Recv
+#endif
+
+int main(int argc, char **argv) {
+
+
+  MPI_Init(NULL, NULL);
+
+
+  int nsize, rank;
+  MPI_Comm_size(DEFAULT_COMM, &nsize);
+  MPI_Comm_rank(DEFAULT_COMM, &rank);
+
+
+
+  int upneighbour = (rank + 1) % nsize;
+  int dnneighbour = (rank + nsize - 1) % nsize;
+
+  int *startdata = malloc(nsize * sizeof(int));
+  for (int i = 0; i < nsize; ++i)
+    startdata[i] = rank;
+  int *dnsend = malloc(nsize * sizeof(int));
+  for (int i = 0; i < nsize; ++i)
+    dnsend[i] = startdata[i] * 1000;
+  int *upsend = malloc(nsize * sizeof(int));
+  for (int i = 0; i < nsize; ++i)
+    upsend[i] = startdata[i];
+  int *uprecv = malloc(nsize * sizeof(int));
+  int *dnrecv = malloc(nsize * sizeof(int));
+
+  for (int i = 0; i < nsize; ++i) {
+    MPI_Request request_up, request_dn;
+    MPI_Isend(upsend, nsize, MPI_INT, upneighbour, 0, DEFAULT_COMM, &request_up);
+    MPI_Isend(dnsend, nsize, MPI_INT, dnneighbour, 0, DEFAULT_COMM, &request_dn);
+
+    MPI_Recv(uprecv, nsize, MPI_INT, upneighbour, 0, DEFAULT_COMM, MPI_STATUS_IGNORE);
+    MPI_Recv(dnrecv, nsize, MPI_INT, dnneighbour, 0, DEFAULT_COMM, MPI_STATUS_IGNORE);
+
+    MPI_Wait(&request_up, MPI_STATUS_IGNORE);
+    MPI_Wait(&request_dn, MPI_STATUS_IGNORE);
+
+    memcpy(dnsend, uprecv, nsize * sizeof(int));
+    memcpy(upsend, dnrecv, nsize * sizeof(int));
+  }
+
+  for (int i = 0; i < nsize; ++i) {
+    MPI_Barrier(DEFAULT_COMM);
+    if (i == rank) {
+      printf("Process %d/%d\n", rank, nsize);
+      for (int i = 0; i < nsize; ++i) {
+	printf("%d ", uprecv[i]);
+      }
+
+      printf("\n");
+      for (int i = 0; i < nsize; ++i) {
+	printf("%d ", dnrecv[i]);
+      }
+
+      printf("\n");
+    }
+  }
+  MPI_Finalize();
+
+  return 0;
+}