<div dir="ltr"><br><div class="gmail_extra"><br><br><div class="gmail_quote">On Fri, Aug 22, 2014 at 6:39 AM, Roland Schulz <span dir="ltr"><<a href="mailto:roland@utk.edu" target="_blank">roland@utk.edu</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><div dir="ltr">Hi,<div><br></div><div>I vaguely remember that someone said there are some plans of generating the verlet kernels in some new way. Do I remember that correctly or do no such plan exist? If they do, what are they?</div>
</div></blockquote><div><br></div><div>Erik has some plans - the general idea is that we use a python script to generate flat source files with no conditionality of any sort, on similar lines to the current group scheme kernel generator.</div>
<div><br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><div dir="ltr"><div>Erik, you mentioned previously that there are potential problems with intrinsics and C++. Do we already have any examples of that?</div>
<div><br></div><div>If C++ and intrinsics doesn't cause any problems one option to replace the preprocessor would be using templated functions (for an example see here: <a href="http://stackoverflow.com/questions/6179295/if-statement-inside-a-cuda-kernel/6179580#6179580" target="_blank">http://stackoverflow.com/questions/6179295/if-statement-inside-a-cuda-kernel/6179580#6179580</a> - this is for CUDA but doesn't effect the idea). </div>
</div></blockquote><div><br></div><div>Yes, that's another way we could metaprogram. I suggested Christian try it out for combining the FFT grids for better LJPME performance (see draft at <a href="https://gerrit.gromacs.org/#/c/3266/11">https://gerrit.gromacs.org/#/c/3266/11</a> in fft5p.cpp for those with access). Inasmuch as constant-propagation and dead-code optimizations probably work fine within a function, even when templated, then I think that's an approach we could use in places. It's definitely better than duplication, and often more readable than preprocessor-based techniques.</div>
<div><br></div><div>The downside for template meta-programming for non-bonded kernels is that you still get a kernel with every possible code path in it, whereas with a generator script doing the metaprogramming, you can read whichever one suits your current purpose. Being able to see the meta-programming output can be useful when developing new kernels. I imagine compile time of ~100 kernels might be a little faster overall with the generator script, and debuggers might have a better time, too.</div>
<div><br></div><div>The downside of generation is having lots of generated code. For the tarball, we should generate the code, but perhaps for the repo we should do it at configure time.<br></div><div><br></div><div><div>
On Anton, they metaprogram even harder - the executables for NPT and NVT are different, for example.</div><div><br></div></div><div>Mark</div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
<div dir="ltr"><span class=""><font color="#888888"><div>Roland<br clear="all"><div><br></div>-- <br>ORNL/UT Center for Molecular Biophysics <a href="http://cmb.ornl.gov" target="_blank">cmb.ornl.gov</a><br>865-241-1537, ORNL PO BOX 2008 MS6309
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<br>--<br>
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