<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:st1="urn:schemas-microsoft-com:office:smarttags" xmlns="http://www.w3.org/TR/REC-html40"> <head> <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=us-ascii"> <meta name=Generator content="Microsoft Word 11 (filtered medium)"> <o:SmartTagType namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="City"/> <o:SmartTagType namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="country-region"/> <o:SmartTagType namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="place"/>  <style>  </style> </head> <body lang=EN-US link=blue vlink=blue> <div class=Section1> Hi David,<o:p></o:p> <o:p> </o:p> Thanks a lot for your help. <o:p></o:p> <o:p> </o:p> Your hints can finally get me started on some useful optimizations. Yes, I can make time measurements using gettimeofday, though the maximum accuracy possible in that is in microseconds. But I believe that should suffice on the ARM.<o:p></o:p> <o:p> </o:p> <div> Thanks.<o:p></o:p> Sandeep Agrawal,<o:p></o:p> Wireless Terminal Division,<o:p></o:p> Samsung <st1:country-region w:st="on"><st1:place w:st="on">India</st1:place></st1:country-region> Software Operations.<o:p></o:p> </div> <div> <div class=MsoNormal align=center style='text-align:center'> <hr size=2 width="100%" align=center tabindex=-1> </div> From: david.freetype@gmail.com [mailto:david.freetype@gmail.com] On Behalf Of David Turner Sent: Thursday, November 01, 2007 2:17 PM To: Sandeep Agrawal Cc: Dan Amelang; cairo@cairographics.org Subject: Re: [<st1:City w:st="on"><st1:place w:st="on">cairo</st1:place></st1:City>] Regarding Cairo Optimization for ARM PXA320<o:p></o:p> </div> <o:p> </o:p> Hi Sandeep,<o:p></o:p> <div> 2007/10/28, Sandeep Agrawal <<a href="mailto:sandeep.a@samsung.com">sandeep.a@samsung.com</a>>:<o:p></o:p> Hi, Actually I am unable to generate profiling data because of certain problems with the platform I am working on. I don't have permissions to create a new device and so opcontrol --init fails. I am new to the text rendering field. Since Monahans does not have an FPU, I made the assumption that the affine transformations happening in floating point may be optimized to work in fixed point. Am I wrong in my assumption?<o:p></o:p> <div> <o:p> </o:p> </div> <div> you would probably be able to optimize the speed of the affine transformation itself, let's say by a factor of 2 (at the cost of reduce precision). However, if this operation only corresponds to say, 5% of your running time, this will only gain you 2.5% of overall time; not necessarily a big win for what could be a lot of work.<o:p></o:p> </div> <div> <o:p> </o:p> </div> <div> please, please use a profiling tool, it will guide you to optimization opportunities. more precisely, it will guide you to the low-hanging fruits, because profile-based optimization usually leads you to some sort of "plateau" which can only be broken by changing your internals drastically. <o:p></o:p> </div> <div> <o:p> </o:p> </div> <div> if you *absolutely* cannot run a profiling tool, I advise you to write profiling tests that basically run the same operation in loops, only varying one parameter at a time. (yes, I'm assuming that you can at least make time measurements in your program). <o:p></o:p> </div> <div> <o:p> </o:p> </div> <div> for example, what is the time to draw 1 glyph, then the time to draw 2, 5, 10, 50, 100 ?<o:p></o:p> </div> <div> do these number scale linearly if all glyphs are identical ? is there a "setup time" that is consistently larger than the increment between two glyph counts ? <o:p></o:p> </div> <div> <o:p> </o:p> </div> <div> what is the time to to draw a string of text at 10pt, 12pt, 14, etc... given that the amount of pixels to be filled grows roughly in n^2 (where n is the size), does the timing follow a similar curve ? <o:p></o:p> </div> <div> <o:p> </o:p> </div> <div> what is the cost of rotating text ? what's the function of performance/angle, etc...<o:p></o:p> </div> <div> <o:p> </o:p> </div> <div> this kind of tests can give you significant information about what's slow and what isn't in a given library, and they're usually pretty easy to write. <o:p></o:p> </div> <div> <o:p> </o:p> </div> <div> and since you also have the <st1:City w:st="on"><st1:place w:st="on">Cairo</st1:place></st1:City> sources to play with, feel free to put time measurements within the library itself to get smaller grained estimates.<o:p></o:p> </div> <div> <o:p> </o:p> </div> <div> maybe that doesn't sound glamorous, but given the conditions you describe, I'm pretty certain it will prove to be more fruitful than a random quest for local optimizations...<o:p></o:p> </div> <div> <o:p> </o:p> </div> <div> hope this helps,<o:p></o:p> </div> <div> <o:p> </o:p> </div> <div> - David Turner<o:p></o:p> </div> <div> <o:p> </o:p> </div> <div>  <o:p></o:p> </div> <blockquote style='border:none;border-left:solid #CCCCCC 1.0pt;padding:0in 0in 0in 6.0pt; margin-left:4.8pt;margin-right:0in'> <o:p> </o:p> If so can you please give some hints as to where I can perform optimizations? I am sure that it would be possible to do some processor specific optimizations as well as <st1:City w:st="on"><st1:place w:st="on">Cairo</st1:place></st1:City> has been written to cater to a large community. Thanks. Sandeep Agrawal, Wireless Terminal Division, Samsung <st1:country-region w:st="on"><st1:place w:st="on">India</st1:place></st1:country-region> Software Operations. -----Original Message----- From: Dan Amelang [mailto:<a href="mailto:daniel.amelang@gmail.com">daniel.amelang@gmail.com </a>] Sent: Saturday, October 27, 2007 12:46 AM To: Sandeep Agrawal Cc: <a href="mailto:cairo@cairographics.org">cairo@cairographics.org</a> Subject: Re: [<st1:City w:st="on"><st1:place w:st="on">cairo</st1:place></st1:City>] Regarding Cairo Optimization for ARM PXA320 On 10/26/07, Sandeep Agrawal <<a href="mailto:sandeep.a@samsung.com">sandeep.a@samsung.com</a>> wrote: > > I am currently optimizing text rendering in <st1:City w:st="on"><st1:place w:st="on">Cairo</st1:place></st1:City> for the PXA320 Monahans > processor. > > I just want to know that is it possible to convert the double computations > (specifically affine) to 16.16 or 26.6 fixed point format (any chance of > overflow or precision loss?) Yes, there is a chance of overflow and precision loss. > or do I have to go with processor specific > assembly optimizations? I don't see how this is an either/or situation. How did converting doubles to fixed-point and using assembly optimizations become your two options for text rendering improvement? I assume that your profiles show that floating-point emulation is the bottleneck? Can you share with us your data? Dan _______________________________________________ <st1:City w:st="on"><st1:place w:st="on">cairo</st1:place></st1:City> mailing list <a href="mailto:cairo@cairographics.org">cairo@cairographics.org</a> <a href="http://lists.cairographics.org/mailman/listinfo/cairo">http://lists.cairographics.org/mailman/listinfo/cairo</a><o:p></o:p> </blockquote> </div> <o:p> </o:p> </div> </body> </html>