Changes between Version 10 and Version 11 of MessagePassing

Timestamp:

07/12/13 15:52:12 (13 years ago)

Author:

siegel

Comment:

--

MessagePassing

@@ -200 +200 @@
  * `int $COMM_ANY_TAG`
 
-
+Here is how these primitives could be used to implement an MPI program:
+
+{{{
+#define MPI_ANY_SOURCE $COMM_ANY_SOURCE
+#define MPI_ANY_TAG $COMM_ANY_TAG
+#define MPI_INT 1
+#define MPI_FLOAT 2
+#define MPI_DOUBLE 3
+// etc.
+
+$input int NPROCS;
+$assume NPROCS >= 1;
+$scope top;
+$proc procs[NPROCS];
+
+typedef $comm *MPI_Comm;
+$comm MPI_Comm_world_comm;
+MPI_Comm *MPI_COMM_WORLD = &_MPI_COMM_WORLD;
+boolean initialized = $false;
+
+/* This structure tells you the source and tag of a received message,
+ * which you need if you used wildcards,  Also size.
+ */
+typedef struct MPI_Status {
+  int source;
+  int tag;
+  int size;
+} MPI_Status;
+
+typedef int MPI_Datatype;
+
+int sizeofDatatype(MPI_Datatype type) {
+  switch (type) {
+    case MPI_INT: return sizeof(int);
+    case MPI_FLOAT: return sizeof(float);
+    case MPI_DOUBLE: return sizeof(double);
+    default: exit(-1); // not yet implemented
+  }
+}
+
+void MPI_Comm_init(MPI_Comm comm) {
+  $when (initialized) ;
+}
+
+void MPI_Send(int pid, void *buf, int count, MPI_Datatype type, int dest, int tag, MPI_Comm comm) {
+  $message m = $message_pack(pid, dest, tag, buf, sizeofDatatype(type)*count);
+
+  $comm_enqueue(comm, &m);
+}
+
+void MPI_Recv(int pid, void *buf, int count, MPI_Datataype type, int source, int tag, MPI_Comm comm, MPI_Status *status) {
+  int size = sizeofDatatype(type)*count;
+  // the following is a system function with built-in guard:
+  $message m = $comm_dequeue(comm, source, pid, tag);
+
+  status->size = $message_size(&m);
+  status->source = $message_source(&m);
+  status->dest = $message_dest(&m);
+  $message_unpack(&m, buf, size); // will throw exception if message too big
+}
+
+void MPI_process(int pid) {
+  ...
+  MPI_Comm_init(MPI_COMM_WORLD);
+  ...
+}
+
+void main() {
+  for (int i=0; i<NPROCS; i++) procs[i] = $spawn MPI_process(i);
+  MPI_Comm_world_comm = $comm_create(NPROCS, &procs[0]);
+  initialized = $true;
+  for (int i=0; i<NPROCS; i++) $wait procs[i];
+}
+}}}
+
+