Btw, I usually use -O3 rather than -O2. I agree with the other poster: I am not sure getting rid of precision is a great idea. Trotter ----- Original Message ---- From: Chris Jones <jonesc@xxxxxxxxxxxxxxxxx> To: For users of Fedora <fedora-list@xxxxxxxxxx> Sent: Friday, August 31, 2007 2:41:56 PM Subject: Re: OT : Approximate / fast math libraries ? Hi, Thanks for your feedback. > What exactly is your need? Contact me off-list and maybe I can > help. Have you profiled your code? I have found that people > often do not actually know where their code is spending its > time. I once sped up an app which was universally acknowledged > to be slow "because it uses floating point." I sped it up 3x. Yes, I have profiled the code, quite extensively, using the valgrind/calltree application. From this I know this that I'm know I've tidying up this to the point where its hard to find big improvements, the cpu time is fairly well spread around, not isolated in a few places. So am now looking a a few places where math calls are taking more time than I would hope. I'm not going to get factors in speed in the overall application, but I hope in a few places things can be improvemed a lot locally. Also, the project is not small, massive in fact, and I'm only writting one small part. If you are interested you can find it here http://lhcb-release-area.web.cern.ch/LHCb-release-area/DOC/brunel/releases/latest/doxygen/index.html It also has to be supported on a *lot* of hardware. Basically gcc 3.2.3 based Scientific Linux 3 machines, gcc 3.4.6 SL4 machines (32 and 64 bit) and (not my decision), windows VC 7.1. I cannot rely on for instance SSE math calls etc. Taking an example from another thread, one place I'm trying to understand is where I use atan2 see http://www.hep.phy.cam.ac.uk/~jonesc/atan2.png for the profiler output. atan2 is taking 50% of the time of this method. Not here I don't need that much precision on the result - say +- O(2*pi/100). Anything you can suggest here - The code is here http://www.hep.phy.cam.ac.uk/~jonesc/RichPhotonRecoUsingCKEstiFromRadius.cpp ( note though its full of internal classes etc...) cheers Chris > > I modified the parsing routines it used, not the floating point. > > Mike > -- > p="p=%c%s%c;main(){printf(p,34,p,34);}";main(){printf(p,34,p,34);} > Oppose globalization and One World Governments like the UN. > This message made from 100% recycled bits. > You have found the bank of Larn. > I can explain it for you, but I can't understand it for you. > I speak only for myself, and I am unanimous in that! -- fedora-list mailing list fedora-list@xxxxxxxxxx To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list ____________________________________________________________________________________ Pinpoint customers who are looking for what you sell. http://searchmarketing.yahoo.com/
