----- Original Message -----
From: "Joe Landman" <[EMAIL PROTECTED]>
To: "Clements, Brent M (SAIC)" <[EMAIL PROTECTED]>
Cc: <beowulf@beowulf.org>
Sent: Thursday, September 28, 2006 2:34 AM
Subject: Re: [Beowulf] Stupid MPI programming question
Hi Brent
Clements, Brent M (SAIC) wrote:
Hey Guys,
I've been sitting here working for the past 48 hours and I'm fighting
a stupid bug in some mpi code I'm working on
How do I broadcast a char string to my slave mpi processes? And how
do I receive that char string and print it out on my slave mpi
process.
This is what I have in my code(some things have been removed)
#define MASTER_RANK 0
char* mystring;
Hmmm.... This makes *mystring a string (ok, a character array), and
mystring a pointer to a character array.
mystring = "some test";
ok ... I haven't played with "strings" recently in C, though I seem to
remember needing a "\0" at the end. RGB is more likely a C language
guru/lawyer than I am, I don't remember off the top of my head if this
is strictly necessary.
If we move to C++ then you have more ways to mess up,
but also methods similar to the above.
Actually in C it would be
#include <string.h>
..
char mystring[1024];
strcpy(mystring,"some test");
MPI_Bcast(&mystring, sizeof(basedir), MPI_CHAR, MASTER_RANK,
MPI_COMM_WORLD);
Lets put on our parser hat. The first argument is
pointer to (pointer to mystring)
mystring is a pointer, *mystring is the (technically) first character in
the array, and &mystring is a pointer to mystring, which is a pointer to
a pointer to the first character in the array.
Ok, if you want to see more of this sort of detail, have a look at
http://course.scalableinformatics.com/lectures/lecture-5/lecture-5.pdf
around page 62 for an example with BCast and Send/Recv pairs. The files
for this lecture are in
http://course.scalableinformatics.com/lectures/lecture-5/source/
in my slave process code I have this
printf("my string I received: %s", mystring);
Am I doing something wrong? Or if someone has some sample code they
can point me to on how to send a string to a slave mpi process and
have that slave mpi process print out the string..that would be even
better. That way..I relearn MPI basics 101
Lots of tutorials on the net, my course and material are up on the net
above.
Joe
--
Joseph Landman, Ph.D
Founder and CEO
Scalable Informatics LLC,
email: [EMAIL PROTECTED]
web : http://www.scalableinformatics.com
phone: +1 734 786 8423
fax : +1 734 786 8452 or +1 866 888 3112
cell : +1 734 612 4615
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