MPICH on Lazarus
lazarus / 13-General

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loro51 · 2008-01-28 21:06

Dear All,

   I'm trying to use the MPICH Lazarus package and creat a simple
program on wich the NODE 0 prints a message asking for the INPUT and
send it to all nodes via MPI_Send, but What happens is that on the Win
CMD console I get FIRST the ReadLn and After the WriteLn.

  I believe that it is a BUFFER problem that I can't see, does any one
done something like this?

   Just to know I'm using an Win 2K with Lazarus v0.9.24 beta. The
package MPICH2 is correctly installed, once the "helloworld.exe"
worked well.

   Here is the code:

Code: [Select]

program ExchangeNum;

{$mode objfpc}{$H+}
{$IFDEF Unix}
{$linklib c}
{$ENDIF}


uses MPI, MPICH2, SysUtils;

var
   myid, size:     integer ;
   dest, source : integer ; // ID
   tag:               integer ;
   MSG:             double  ;
    
   Status:        MPI_Status ;
  
begin

  tag:= 50 ;
 
  MPI_Init(@argc, @argv);
  MPI_Comm_rank(MPI_COMM_WORLD, @myid);
  MPI_Comm_size(MPI_COMM_WORLD, @size);
 
  If (myid = 0) then begin
     WriteLn('Write the MSG (double)');
     Readln(MSG);
     WriteLn('NODE ',myid, ' MSG = ',MSG:2:5);
     For dest:= 1 to (size-1) do
          MPI_Send(@MSG, SizeOf(MSG), MPI_FLOAT, dest, tag,
MPI_COMM_WORLD);
  End
  Else begin
       source:=0;
       MPI_Recv(@MSG, SizeOf(MSG), MPI_FLOAT, source, tag,
MPI_COMM_WORLD, @status);
       Writeln('NODE ',myid, ' MPI_Recv = ',MSG:2:5);
  End;
      
  MPI_Finalize;
end.                 


the command on the CMD is:

mpiexec -n 4 \\MASTER\ExchangeNum\ExchangeNum.exe

Thanks

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loro51 · 2008-01-29 21:12

As you probably can see it is missing something

Code: [Select]
   WriteLn(StdOut, 'Write the MSG (double)');
   Flush(StdOut);
   ReadLn(MSG);



Every time I write a WriteLn it is necessary to Flush all the
information from the Buffer, besides onusing the WriteLn it is
necessary to set what is the Text so that the buffer can go to. Here
it is used the StdOut.

Hugs