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First commit. VS2013, Codeblocks and Mac OSX configuration
author Geogaddi\David <d.m.ronan@qmul.ac.uk>
date Thu, 09 Jul 2015 01:12:16 +0100
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+<html lang="en">
+<head>
+<title>Cell Caveats - FFTW 3.2.1</title>
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+<link rel="up" href="FFTW-on-the-Cell-Processor.html#FFTW-on-the-Cell-Processor" title="FFTW on the Cell Processor">
+<link rel="prev" href="Cell-Installation.html#Cell-Installation" title="Cell Installation">
+<link rel="next" href="FFTW-Accuracy-on-Cell.html#FFTW-Accuracy-on-Cell" title="FFTW Accuracy on Cell">
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+<!--
+This manual is for FFTW
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+Copyright (C) 2003 Matteo Frigo.
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+</head>
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+<div class="node">
+<p>
+<a name="Cell-Caveats"></a>
+Next:&nbsp;<a rel="next" accesskey="n" href="FFTW-Accuracy-on-Cell.html#FFTW-Accuracy-on-Cell">FFTW Accuracy on Cell</a>,
+Previous:&nbsp;<a rel="previous" accesskey="p" href="Cell-Installation.html#Cell-Installation">Cell Installation</a>,
+Up:&nbsp;<a rel="up" accesskey="u" href="FFTW-on-the-Cell-Processor.html#FFTW-on-the-Cell-Processor">FFTW on the Cell Processor</a>
+<hr>
+</div>
+
+<h3 class="section">6.2 Cell Caveats</h3>
+
+     <ul>
+<li>The FFTW benchmark program allocates memory using malloc() or
+equivalent library calls, reflecting the common usage of the FFTW
+library.  However, you can sometimes improve performance significantly
+by allocating memory in system-specific large TLB pages.  E.g., we
+have seen 39 GFLOPS/s for a 256&nbsp;&times;&nbsp;256&nbsp;&times;&nbsp;256 problem using
+large pages, whereas the speed is about 25 GFLOPS/s with normal pages. 
+YMMV.
+
+     <li>FFTW hoards all available SPEs for itself.  You can optionally
+choose a different number of SPEs by calling the undocumented
+function <code>fftw_cell_set_nspe(n)</code>, where <code>n</code> is the number of desired
+SPEs.  Expect this interface to go away once we figure out how to
+make FFTW play nicely with other Cell software.
+
+     <p>In particular, if you try to link both the single and double precision
+of FFTW in the same program (which you can do), they will both try
+to grab all SPEs and the second one will hang.
+
+     <li>The SPEs demand that data be stored in contiguous arrays aligned at
+16-byte boundaries.  If you instruct FFTW to operate on
+noncontiguous or nonaligned data, the SPEs will not be used,
+resulting in slow execution.  See <a href="Data-Alignment.html#Data-Alignment">Data Alignment</a>.
+
+     <li>The <code>FFTW_ESTIMATE</code> mode may produce seriously suboptimal plans, and
+it becomes particularly confused if you enable both the SPEs and
+Altivec.  If you care about performance, please use <code>FFTW_MEASURE</code>
+or <code>FFTW_PATIENT</code> until we figure out a more reliable performance model.
+
+</ul>
+
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+</body></html>
+