Charm++ parallel programming system

[Chao Mei <chaomei2 AT illinois.edu>]

TLS will work, here's paper about its usage in AMPI ( http://charm.cs.uiuc.edu/papers/11-23)

 

In addition, in charm++, we also use TLS ("__thread" if supported by compiler and OS) for processor private variables (Cpvs) for the multithreaded runtime.

 

-Chao

From: Fernando Stump

Sent: Friday, October 21, 2011 12:02 PM

To: Phil Miller ; Charm Mailing List

Subject: Re: [ppl] [charm] multi-thread in taub

Hi,

I have another question related to multi-threading. here it is:

My Problem: My original serial code uses a lot of  static variables / static member functions . To preserve the semantics of the code, I would like that this static variables are local to each thread. (i.e. If I create a static variable inside driver()) each driver will. see a static variable)

Solutions:

Aaron proposed this solution:

You're right, this is a potential source of errors--all drivers on a
processor will share any static members. One workaround to this issue
if you
need to keep the static members is to replace your static
property_set with a static map<int, property_set> which has an entry
for each chare on the processor. So, instead of accessing
set_.whatever(), you would instead access set_[CkMyPE()].whatever().
This has potentially bad cache behavior, but it does allow you to
retain the static variables and still get correct results.

Googling I found another potential solution and I would like to hear your opinions:

Solution :  Use the specifier __thread

As in

static __thread char *p;

Here it is the documentation of this specifier at gcc 

http://gcc.gnu.org/onlinedocs/gcc-4.1.2/gcc/Thread_002dLocal.html

Is there a chance it will work? I do not understande very well how does ParFUM/Charm++ create threads or assign Chares/Driver() to threads.

Thanks

Fernando

On Oct 7, 2011, at 2:40 PM, Phil Miller wrote:

On Fri, Oct 7, 2011 at 14:22, Fernando Stump <fernando.stump AT gmail.com> wrote:

Hi,

I'm running my ParFUMized version of my code at the taub cluster at uiuc.  Each node contains 12 processors. I'm running in one node, with option +p2, but I have the feeling that the code is running in a single processor. My clue is that this is related with this "warning"

Charm++> Running on MPI version: 2.2 multi-thread support: 0 (max supported: -1)

This is a detail of the underlying MPI implementation. It doesn't mean
Charm++ is running on only 1 thread.

My question is:

Where it is the issue?  Is it on how MPI was compiled or on how charm++ was compiled or on how I call charmrun?

Here it is the full call.

[fstump2@taubh2 io]$ ../yafeq/build/debug/yafeq/charmrun ../yafeq/build/debug/yafeq/pfem.out +p2

Running on 2 processors:  ../yafeq/build/debug/yafeq/pfem.out

charmrun>  /usr/bin/setarch x86_64 -R  mpirun -np 2  ../yafeq/build/debug/yafeq/pfem.out

Charm++> Running on MPI version: 2.2 multi-thread support: 0 (max supported: -1)

Charm++> Running on 1 unique compute nodes (12-way SMP).

Charm++> Cpu topology info:

PE to node map: 0 0

Node to PE map:

Chip #0: 0 1

Charm++> cpu topology info is gathered in 0.003 seconds.

This output seems to indicate that things are working correctly. You
got two cores, 0 and 1, on chip 0 of node 0. Did some other indication
lead you to the conclusion that only one core was doing work?

Phil

---

_______________________________________________
charm mailing 
list
charm AT cs.uiuc.edu
http://lists.cs.uiuc.edu/mailman/listinfo/charm

---

_______________________________________________
ppl mailing 
list
ppl AT cs.uiuc.edu
http://lists.cs.uiuc.edu/mailman/listinfo/ppl