qthread_fork_{*} and nested thread safety

[John Leidel]

All, quick question about the safety of nested parallel regions in qthreads.  Is it safe/permissible to nest calls to one or more of the qthread_fork_{*}() routines?  [I'm not familiar with qthreads' rules of scoping] 

EG: 

#-- BAR

aligned_t bar( void )

{

    //-- do stuff

}

#-- FOO

aligned_t foo( void )

{

   qthread_fork( bar(), .., .. );

}

#-- MAIN 

int main( )

{

qthread_initialize();

qthread_fork( foo(), .. , .. )

....

}

--
John D. Leidel
Software Architect
Convey Computer
jle...@conveycomputer.com
(g) 972.836.7901
(m) 214.578.8510

[Stark, Dylan]

John,

On Jan 12, 2012, at 2:59 PM, John Leidel wrote:

All, quick question about the safety of nested parallel regions in qthreads.  Is it safe/permissible to nest calls to one or more of the qthread_fork_{*}() routines?  [I'm not familiar with qthreads' rules of scoping] 

Your example pseudocode is certainly safe/permissible with respect to nesting. Each call to qthread_for_{*}() simply creates a new asynchronous task that is added to a work queue and scheduled to execute by the runtime. Your primary concern would be making sure that you set up your synchronization such that all spawned tasks finish before qthread_finalize() is called or main() exits. Aside from that, there are no explicit dependencies between tasks that are managed by Qthreads.

You might check out `<qthreads>/test/benchmarks/generic/time_fib.c` for a simple example of nested spawns.

EG: 

#-- BAR

aligned_t bar( void )

{

    //-- do stuff

}

#-- FOO

aligned_t foo( void )

{

   qthread_fork( bar(), .., .. );

}

#-- MAIN 

int main( )

{

qthread_initialize();

qthread_fork( foo(), .. , .. )

....

}

--
John D. Leidel
Software Architect
Convey Computer
jle...@conveycomputer.com
(g) 972.836.7901
(m) 214.578.8510

Dylan Stark

Scalable Computer Architectures Dept

Sandia National Laboratories