<div dir="ltr">Hi Alberto!<br><br><div class="gmail_quote">On Wed, Mar 10, 2010 at 9:55 AM, Alberto Mardegan <span dir="ltr"><<a href="mailto:mardy@users.sourceforge.net">mardy@users.sourceforge.net</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">Hi all,<br>
in maemo-mapper I have a lot of code involved in doing transformations from latitude/longitude to Mercator coordinates (used in google maps, for example), calculation of distances, etc.<br>
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I'm trying to use integer arithmetics as much as possible, but sometimes it's a bit impractical, and I wonder if it's really worth the trouble.<br>
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Does one have any figure about how the performance of the FPU is, compared to integer operations?<br>
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A practical question: should I use this way of computing the square root:<br>
<br>
<a href="http://en.wikipedia.org/wiki/Methods_of_computing_square_roots#Binary_numeral_system_.28base_2.29" target="_blank">http://en.wikipedia.org/wiki/Methods_of_computing_square_roots#Binary_numeral_system_.28base_2.29</a><br>
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(but operating on 32 or even 64 bits), or would I be better using sqrtf() or sqrt()?<br>
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Does anyone know any tricks to optimize certain operations on arrays of data?<br></blockquote><div><br></div><div><br></div><div>Basically, what we did with ThinX OS, is have a full blown soft-float toolchain which then used the already proven and highly optimized GCC's stack floating point operations. However , Maemo is not soft float, so I'd recommend to experiment with rebuilding Mapper using such a soft float enabled toolchain, statically linked to avoid glitches to system's libc or have a seperat LD_LIBRARY_PATH to avoid memory hogging, and see where it gets you.</div>
<div><br></div><div>IMHO this is the best way to do FP optimization. We have experimented with it alot, including sqrtf and friend to no significant improvement.</div><div><br></div><div>Sivan</div><div> </div></div></div>