Hi, Hajime,

MPI spec also says "valuelen is the number of characters available in value". So it seems if you should pass valuelen = 4 if value is a buffer of 4 bytes.

I am also confused by "In C, valuelen should be one less than the amount of allocated space to allow for the null terminator". So I leave the question for others.

Interestingly, for MPI_Info_get_valuelen(), MPI spec says "The length returned in C does not include the end-of-string".

BTW, I found MPICH and OpenMPI have the same behavior.

--Junchao Zhang

On Sun, Feb 1, 2015 at 12:13 AM, Hajime Fujita <hfujita@uchicago.edu> wrote:

Hello,

I came across some question about a behavior of MPI_Info_get in MPICH.

If I knew the size of the value, what should I pass to MPI_Info_get as `valuelen`?
Suppose I have 3-byte value in the info object, and I allocate 4-byte buffer including a space for null-termination. Then I think I should specify 3 as valuelen to retrieve the whole value, as the MPI-3 specifications says
"In C, valuelen should be one less than the amount of allocated space to allow for the null terminator.”

However, when I run the attached program in MPICH 3.1.1, I get:
$ ./test
key found: vaule=va # The last character ‘l’ is missing

If I specify `sizeof(buff)` as valuelen, it shows “val” correctly.

So apparently MPICH thinks valuelen includes null terminator.
Am I missing anything, or any misunderstanding here?

Thank you in advance,
Hajime

--
Hajime Fujita
Postdoctoral Scholar, Large-Scale Systems Group
Department of Computer Science, The University of Chicago
http://www.cs.uchicago.edu/people/hfujita
_______________________________________________
discuss mailing list discuss@mpich.org
To manage subscription options or unsubscribe:
https://lists.mpich.org/mailman/listinfo/discuss