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<p>Hello.</p>
<p>In the past weeks I worked on the inclusion of experimental
thread-safety support (mostly based on the work by Maxim Gaina) in
the "devel" branch of the Parma Polyhedra Library.</p>
A few relevant information:
<p>- as said above, thread-safety support is only available in the
git branch named "devel"<br>
</p>
<p>- in order to enable support for thread-safety, the library has
to be configured using option "--enable-thread-safe"<br>
</p>
<p>- it assumes a compiler supporting C++11 threads (tested only
with gcc on linux)<br>
</p>
<p>- currently thread-safety is only available when using the C++, C
and Java language interfaces<br>
</p>
<p>- the timeout mechanism does NOT support thread safety (yet)<br>
</p>
<p>- a few examples of computations using multiple PPL threads can
be found in:<br>
* demos/ppl_lcdd (for the C++ interface)<br>
* demos/ppl_lpsol (for the C interface)<br>
* interfaces/Java/tests/Variable_Output_thread_safe1.java<br>
</p>
<p>- it is worth stressing (again) that the library is
*conditionally* thread safe: if any two application threads share
library objects, the application should manage to properly
serialize all accesses to these objects (note: even when all these
accesses are meant to be read-only, because many PPL operators are
"logically const", but may actually modify the internal
representation of objects, therefore leading to race conditions)</p>
<p>- beware of inefficiencies coming from memory allocation; we
suggest to replace the standard allocation mechanism with
something that behaves better in a multi-threaded setting (e.g.,
TCMalloc).</p>
It would be nice if people interested in this extension could give
it a try and provide us with some feedback.<br>
<br>
Enea.<br>
<br>
<br>
<div class="moz-cite-prefix">On 08/10/2016 09:59 AM, Enea Zaffanella
wrote:<br>
</div>
<blockquote
cite="mid:d1939ec5-3807-396c-6d78-9baed181038e@cs.unipr.it"
type="cite">
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<p>Hello John.</p>
<p>The library, as is, is not thread safe (the main reason is that
it uses a bunch of static caches to speed up single-threaded
computations).<br>
</p>
<p>Maxim Gaina, a student under my supervision, produced a version
of the library which is conditionally thread safe: safety is
achieved as long as each thread has exclusive access to the PPL
objects it works on. That is, either the objects are not shared
between threads or the application code makes sure that shared
objects are accessed at different times (e.g., using mutexes).
The thread-safe version uses C++11 constructs and it was
considering the C++ and C language interfaces only. For testing
purposes, Maxim produced multi-threaded variants of demo
programs ppl_lcdd and ppl_lpsol. <br>
</p>
<p>Afaict, Roberto was considering whether or not the work of
Maxim was to be added to the main PPL library.</p>
<p>Cheers,<br>
Enea<br>
</p>
<br>
<div class="moz-cite-prefix">On 08/09/2016 11:23 PM, John Paulson
wrote:<br>
</div>
<blockquote
cite="mid:CAGZnXMjo5K9QBfXDaoWAXwJJ=oDkqSyLkMuwDL5=Cv9R9V7e6g@mail.gmail.com"
type="cite">
<div dir="ltr">Hi Developers,
<div><br>
</div>
<div>I have been using PPL for a couple of years, and I have
just become interested in parallelizing an application I
wrote that calls it. I tried to do this (using a
parallel_for loop from TBB), but I ran into varied errors at
run time.</div>
<div><br>
</div>
<div>I noticed that in the TODO file of the PPL distribution
that it has "Make the library thread-safe" on the list. Has
this been done yet? Would the lack of thread safety lead to
strange run time errors?</div>
<div><br>
</div>
<div><br>
</div>
<div>Best,</div>
<div>John C. Paulson</div>
</div>
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