[SMPI] Improved several comments in the code

[simgrid.git] / src / smpi / smpi_base.c

diff --git a/src/smpi/smpi_base.c b/src/smpi/smpi_base.c
index bc7ac71..76e98d8 100644 (file)
--- a/src/smpi/smpi_base.c
+++ b/src/smpi/smpi_base.c
@@ -7,6 +7,7 @@
 #include "private.h"
 #include "xbt/virtu.h"
 #include "mc/mc.h"
 #include "private.h"
 #include "xbt/virtu.h"
 #include "mc/mc.h"

+#include "mc/mc_replay.h"

 #include "xbt/replay.h"
 #include <errno.h>
 #include "simix/smx_private.h"
 #include "xbt/replay.h"
 #include <errno.h>
 #include "simix/smx_private.h"


@@ -195,7 +196,12 @@ double smpi_mpi_wtime(){
   if (smpi_process_initialized() && !smpi_process_finalized() && !smpi_process_get_sampling()) {
     smpi_bench_end();
     time = SIMIX_get_clock();
   if (smpi_process_initialized() && !smpi_process_finalized() && !smpi_process_get_sampling()) {
     smpi_bench_end();
     time = SIMIX_get_clock();

-    //to avoid deadlocks if called too many times
+    // to avoid deadlocks if used as a break condition, such as
+    //     while (MPI_Wtime(...) < time_limit) {
+    //       ....
+    //     }
+    // because the time will not normally advance when only calls to MPI_Wtime
+    // are made -> deadlock (MPI_Wtime never reaches the time limit)

     if(smpi_wtime_sleep > 0) simcall_process_sleep(smpi_wtime_sleep);
     smpi_bench_begin();
   } else {
     if(smpi_wtime_sleep > 0) simcall_process_sleep(smpi_wtime_sleep);
     smpi_bench_begin();
   } else {


@@ -456,11 +462,11 @@ void smpi_mpi_start(MPI_Request request)
         oldbuf = request->buf;
         if (!smpi_process_get_replaying() && oldbuf && request->size!=0){
           if((smpi_privatize_global_variables)
         oldbuf = request->buf;
         if (!smpi_process_get_replaying() && oldbuf && request->size!=0){
           if((smpi_privatize_global_variables)

-             && ((char*)request->buf >= start_data_exe)
-             && ((char*)request->buf < start_data_exe + size_data_exe )){
+            && ((char*) request->buf >= smpi_start_data_exe)
+            && ((char*)request->buf < smpi_start_data_exe + smpi_size_data_exe )){

             XBT_DEBUG("Privatization : We are sending from a zone inside global memory. Switch data segment ");
             XBT_DEBUG("Privatization : We are sending from a zone inside global memory. Switch data segment ");

-                   smpi_switch_data_segment(request->src);
-         }
+            smpi_switch_data_segment(request->src);
+          }

           buf = xbt_malloc(request->size);
           memcpy(buf,oldbuf,request->size);
           XBT_DEBUG("buf %p copied into %p",oldbuf,buf);
           buf = xbt_malloc(request->size);
           memcpy(buf,oldbuf,request->size);
           XBT_DEBUG("buf %p copied into %p",oldbuf,buf);


@@ -694,8 +700,8 @@ static void finish_wait(MPI_Request * request, MPI_Status * status)
     if((req->flags & ACCUMULATE) || (datatype->has_subtype == 1)){
       if (!smpi_process_get_replaying()){
         if( smpi_privatize_global_variables
     if((req->flags & ACCUMULATE) || (datatype->has_subtype == 1)){
       if (!smpi_process_get_replaying()){
         if( smpi_privatize_global_variables

-            && ((char*)req->old_buf >= start_data_exe)
-            && ((char*)req->old_buf < start_data_exe + size_data_exe )
+            && ((char*)req->old_buf >= smpi_start_data_exe)
+            && ((char*)req->old_buf < smpi_start_data_exe + smpi_size_data_exe )

         ){
             XBT_VERB("Privatization : We are unserializing to a zone in global memory - Switch data segment ");
             smpi_switch_data_segment(smpi_process_index());
         ){
             XBT_VERB("Privatization : We are unserializing to a zone in global memory - Switch data segment ");
             smpi_switch_data_segment(smpi_process_index());


@@ -743,8 +749,12 @@ int smpi_mpi_test(MPI_Request * request, MPI_Status * status) {
 
   //assume that request is not MPI_REQUEST_NULL (filtered in PMPI_Test or smpi_mpi_testall before)
 
 
   //assume that request is not MPI_REQUEST_NULL (filtered in PMPI_Test or smpi_mpi_testall before)
 

-  //to avoid deadlocks
-  //multiplier to the sleeptime, to increase speed of execution, each failed test will increase it
+  // to avoid deadlocks if used as a break condition, such as
+  //     while (MPI_Test(request, flag, status) && flag) {
+  //     }
+  // because the time will not normally advance when only calls to MPI_Test
+  // are made -> deadlock
+  // multiplier to the sleeptime, to increase speed of execution, each failed test will increase it

   static int nsleeps = 1;
   if(smpi_test_sleep > 0)  simcall_process_sleep(nsleeps*smpi_test_sleep);
 
   static int nsleeps = 1;
   if(smpi_test_sleep > 0)  simcall_process_sleep(nsleeps*smpi_test_sleep);
 


@@ -853,8 +863,9 @@ void smpi_mpi_iprobe(int source, int tag, MPI_Comm comm, int* flag, MPI_Status*
   MPI_Request request =build_request(NULL, 0, MPI_CHAR, source == MPI_ANY_SOURCE ? MPI_ANY_SOURCE : smpi_group_index(smpi_comm_group(comm), source), smpi_comm_rank(comm), tag,
             comm, PERSISTENT | RECV);
 
   MPI_Request request =build_request(NULL, 0, MPI_CHAR, source == MPI_ANY_SOURCE ? MPI_ANY_SOURCE : smpi_group_index(smpi_comm_group(comm), source), smpi_comm_rank(comm), tag,
             comm, PERSISTENT | RECV);
 

-  //to avoid deadlock, we have to sleep some time here, or the timer won't advance and we will only do iprobe simcalls
-  //multiplier to the sleeptime, to increase speed of execution, each failed iprobe will increase it
+  // to avoid deadlock, we have to sleep some time here, or the timer won't advance and we will only do iprobe simcalls
+  // (especially when used as a break condition, such as while(MPI_Iprobe(...)) ... )
+  // multiplier to the sleeptime, to increase speed of execution, each failed iprobe will increase it

   static int nsleeps = 1;
   if(smpi_iprobe_sleep > 0)  simcall_process_sleep(nsleeps*smpi_iprobe_sleep);
   // behave like a receive, but don't do it
   static int nsleeps = 1;
   if(smpi_iprobe_sleep > 0)  simcall_process_sleep(nsleeps*smpi_iprobe_sleep);
   // behave like a receive, but don't do it