+#include <stdio.h>
+#include <mpi.h>
+#include <simgrid/modelchecker.h>
+
+#define GRANT_TAG 0
+#define REQUEST_TAG 1
+#define RELEASE_TAG 2
+
+int main(int argc, char **argv){
+
+ int err, size, rank;
+ int recv_buff;
+ MPI_Status status;
+ int CS_used = 0;
+ xbt_dynar_t requests = xbt_dynar_new(sizeof(int), NULL);
+
+ /* Initialize MPI */
+ err = MPI_Init(&argc, &argv);
+ if(err != MPI_SUCCESS){
+ printf("MPI initialization failed !\n");
+ exit(1);
+ }
+
+ MC_ignore(&(status.count), sizeof(status.count));
+
+ /* Get number of processes */
+ err = MPI_Comm_size(MPI_COMM_WORLD, &size);
+ /* Get id of this process */
+ err = MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+
+ if(rank == 0){ /* Coordinator */
+ while(1){
+ MPI_Recv(&recv_buff, 1, MPI_INT, MPI_ANY_SOURCE, MPI_ANY_TAG, MPI_COMM_WORLD, &status);
+ if(status.MPI_TAG == REQUEST_TAG){
+ if(CS_used){
+ printf("CS already used. Queue the request.\n");
+ xbt_dynar_push(requests, &recv_buff);
+ }else{
+ printf("CS idle. Grant immediatly.\n");
+ MPI_Send(&rank, 1, MPI_INT, recv_buff, GRANT_TAG, MPI_COMM_WORLD);
+ CS_used = 1;
+ }
+ }else{
+ if(!xbt_dynar_is_empty(requests)){
+ printf("CS release. Grant to queued requests (queue size: %lu)",
+ xbt_dynar_length(requests));
+ xbt_dynar_shift(requests, &recv_buff);
+ MPI_Send(&rank, 1, MPI_INT, recv_buff, GRANT_TAG, MPI_COMM_WORLD);
+ CS_used = 1;
+ }else{
+ printf("CS release. Resource now idle.\n");
+ CS_used = 0;
+ }
+ }
+ }
+ }else{ /* Client */
+ while(1){
+ printf("%d asks the request.\n", rank);
+ MPI_Send(&rank, 1, MPI_INT, 0, REQUEST_TAG, MPI_COMM_WORLD);
+
+ MPI_Recv(&recv_buff, 1, MPI_INT, 0, MPI_ANY_TAG, MPI_COMM_WORLD, &status);
+
+ printf("%d got the answer. Release it.\n", rank);
+ MPI_Send(&rank, 1, MPI_INT, 0, RELEASE_TAG, MPI_COMM_WORLD);
+
+ }
+ }
+
+ MPI_Finalize();
+
+ return 0;
+}
