[mpich-discuss] For beginning MPI users...

[Ganesh]

Hi,

I am new to this group, and notice that many folks are learning how to 
program in MPI. I have a small tip for them.

Once they get their code to compile (*), they may wish to try using ISP 
which was announced in this list just recently. ISP is extremely easy to 
use (its user manual shows the 2-3 commands you need - i.e. you do ispcc 
instead of mpicc , and ispcc calls mpicc from within -- etc.)

Once you run even your simplest MPI programs using ISP, you can watch 
all the possible send/receive matches etc. graphically. In fact, much 
more than a debugger, it shows all possible interleavings, and for each 
interleaving (execution possibility) it shows what send / receive 
matches can occur. ISP's Java GUI has tool tips and you can also watch 
the source lines using the source window. The source window has  tabbed 
and split views, and you can further see the communication matches 
through color codes.

You may also place C "assert" statements within your code, and ISP will 
check those assertions for all possible executions of your code. Finally 
you may catch deadlocks and MPI object leaks. All this for doing "ispcc" 
instead of "mpicc"

(see user manual at
http://www.cs.utah.edu/formal_verification/ISP-release )

If you follow the instructions in our user manual and run into problems, 
we will be most happy to help you.

Ganesh Gopalakrishnan

(*) well, you can even provide a "raw" file to ISP . ISP calls MPICH 
from within, and arranges for a lot of the environment settings and 
flags. So you can even see all the "file not found" messages and correct 
them from within ISP.  Once your code runs OK in ISP, then you can shift 
the code to a larger cluster and do your performance tuning experiments. 
That is, it may be easier to get rid of "file not found"s as well as 
deadlocks from within ISP.

p.s. For those doing MPI code development for their research / classes, 
we are very eager to work with you. We want to see how ISP fares, 
whether it does not work as advertised, or if it surprised you by 
finding a bug. Please drop us a note and we will work with you!

Our email is isp-dev at cs.utah.edu

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