MPI_Get_count returning negative value for count

Question

Can MPI_Get_count() return a negative value for the count? My message sizes never exceed 1138 integers. So it should not be a problem with the message length.

    if(MPI_Probe(MPI_ANY_SOURCE,0,MPI_COMM_WORLD,&status) == MPI_SUCCESS)
    {
     printf("probe flag true\n");
     MPI_Get_count(&status,MPI_DOUBLE,&recv_size);
    }

The value of recv_size I get is negative.

Declaration of recv_size, please?

Tomasz Kowalczyk
– Tomasz Kowalczyk

2012-06-14 22:03:39 +00:00
Commented Jun 14, 2012 at 22:03 — Tomasz Kowalczyk
– Tomasz Kowalczyk, Commented Jun 14, 2012 at 22:03
recv_size is declared as an integer.

ap040
– ap040

2012-06-15 07:54:25 +00:00
Commented Jun 15, 2012 at 7:54 — ap040
– ap040, Commented Jun 15, 2012 at 7:54
MPI_UNDEFINED is -32766 in both Open MPI and Intel MPI.

Hristo Iliev
– Hristo Iliev

2012-06-15 07:57:06 +00:00
Commented Jun 15, 2012 at 7:57 — Hristo Iliev
– Hristo Iliev, Commented Jun 15, 2012 at 7:57

timos · Accepted Answer · 2012-06-14 22:08:43Z

1

MPI_Get_count will return MPI_UNDEFINED (which is most likely negative) iff the message size is not a multiple of the size of the datatype given to MPI_Get_count. So maybe you are sending 5 Bytes as MPI_BYTE but you ask MPI_Get_count how many MPI_DOUBLES you received.

answered Jun 14, 2012 at 22:08

timos

2,7171 gold badge20 silver badges21 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

ap040 Over a year ago

This is my declaration of mpi_send : MPI_Send(T,(m->ncols),MPI_DOUBLE,map(j,procs),0,MPI_COMM_WORLD);

ap040 · Accepted Answer · 2012-06-15 08:08:32Z

0

I just realised that it was a problem with the data I was sending. The values exceeded the sizeof double. Fixed it and the code worked. Thanks for the help and sorry for buggy code!

answered Jun 15, 2012 at 8:08

ap040

1211 silver badge5 bronze badges

Collectives™ on Stack Overflow

MPI_Get_count returning negative value for count

2 Answers 2

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related