Re: [Cs-dev] Vectorization

Date	2008-04-17 04:22
From	"Michael Gogins"
Subject	Re: [Cs-dev] Vectorization
	I've done a bit of profiling; gprof is not completely satisfactory, since I am used to sunstudio on Solaris, so far superior it makes one shake one's head. On Solaris, the Sun compiler automatically builds code for profiling, and samples code by line from the kernel to give complete timing for each line of source code, as well as the call graphs supported by gprof. This is very useful... At any rate, it's clear enough that almost all time in csound examples/xanadu.csd is going into kperf and opcodes called by kperf, and quite negligible amounts into reading orc and sco, printing messages, or writing the output soundfile. kperf in itself takes about 23% of the time not counting its callees, and in turn fairly evenly divides its callees' time between the opcodes, which include not only pluck, klinseg, oscillators, and delay lines, but also krate-arate, arate-krate, and arate-arate arithmetic. Since the kperf loop looks pretty minimal, I have no idea why its own code should be eating 23% of the performance time. That is my major question at this point. I may need to rewrite kperf as a set of functions to obtain a more detailed breakdown of this time. Or I can develop some insight in the debugger. On Linux, you can rebuild the kernel and use oprofile, which can do what sunstudio can do, and give line by line timings inside functions. I will also profile Trapped in Convert since it performs many more short events, in comparison with Xanadu which performs a few long guitar-like chords. Regards, Mike ----- Original Message ----- From: "Steven Yi" To: "Developer discussions" Sent: Wednesday, April 16, 2008 8:21 PM Subject: Re: [Cs-dev] Vectorization > Hi Victor, > > I haven't done it in a long time, but I found an email I posted to the > dev list a year and a half ago that has some instructions: > > http://www.nabble.com/Call-Graph-%28Postscript-file%29-td5730328.html#a5730328 > > I haven't run it in a long while but those commands that were run > there should do the trick. > > steven > > On Wed, Apr 16, 2008 at 12:33 PM, victor wrote: >> I built csound with useGprof=1, run a simple one-oscillator test, then >> tried gprof and got an empty profile. Why is that? >> >> >> ----- Original Message ----- >> From: "Steven Yi" >> >> To: "Michael Gogins" ; "Developer discussions" >> >> >> >> Sent: Wednesday, April 16, 2008 7:42 PM >> Subject: Re: [Cs-dev] Vectorization >> >> >> > Hi Michael, >> > >> > I'm interested in the profiling results; what profiler are you using >> > by the way? I remember doing profiling a while back using debug >> > builds and gprof (the options for that are still in SConstruct), but >> > when I did profiling it was more for to try to figure out why the >> > Pinkston FM model was really slow at the time, not so much for general >> > Csound performance. >> > >> > I've poked around most of Csound's engine and feel like I know it >> > pretty well, especially when I was more actively working on the new >> > parser. If there's any questions that arise about Csound internals >> > and how things are allocated, I'd suggest looking at the new parser >> > (well, the compile part that translates the AST to the INSTRTXT data >> > structs that Csound uses at performance time) to see how things are >> > built, as to me it's a bit clearer than reading the old parser code. >> > >> > steven >> > >> > >> > On Wed, Apr 16, 2008 at 11:27 AM, Michael Gogins >> > wrote: >> >> Yes, this is interesting. I have not yet tried unsafe math >> optimizations, >> >> but will. >> >> >> >> I have tried inlining as much code as possible, which in practice >> means >> >> defining all C++ member functions in the header file. That >> consistently >> >> produces somewhere between 5% and 15% speedups, right there. >> >> >> >> This in is the context of intermittently continuing development of >> >> Silence, an algorithmic composition/software synthesis library of my >> own >> >> design. Currently, Silence renders audio just slightly faster than >> >> Csound, but this is with hard-coded STK Rhodey C++ instruments. (But >> >> then, my comparison Csound instrument uses the STK Rhodey opcode >> also, so >> >> the comparison is more fair than it might seem: it mostly compares >> >> instrument allocation and event dispatching). Dynamically defined >> >> instruments will be slower in Silence, perhaps also in Csound (i.e., >> >> using more opcodes in the instr block instead of just calling one >> opcode >> >> that does all the work). I shall soon know more, as I have finalized >> my >> >> design of dynamically defined instruments and unit generators in >> Silence. >> >> >> >> It is the usefulness of the profiler in getting this performance >> that >> >> has decided me to profile Csound. I am very curious to see how much >> >> "slack" there is, how much scope for performance improvements. Most >> of >> >> Csound's opcodes code looks to be quite efficient, and I am certainly >> not >> >> going to monkey with the fundamental design of the engine, so I am >> most >> >> curious about the efficiency of the engine implementation, especially >> the >> >> kperf loop, event initializers, output drivers, and so on. I don't, >> >> actually, expect much slack but the profiler will, perhaps, point out >> a >> >> few areas that have not been completely thought through. >> >> >> >> Regards, >> >> Mike >> >> >> >> >> >> >> >> -----Original Message----- >> >> >From: Steven Yi >> >> >Sent: Apr 16, 2008 12:00 PM >> >> >To: Developer discussions >> >> >Subject: [Cs-dev] Vectorization >> >> > >> >> >Hi All, >> >> > >> >> >There's an interesting thread going on on linux-audio-dev about the >> >> >performance of gcc vectorization code: >> >> > >> >> >http://www.nabble.com/vectorization-td15339532.html#a16720581 >> >> > >> >> >The thread started in February but resumed a day or two ago, with >> >> >someone reporting better results with gcc than using assembly. >> >> > >> >> >steven >> >> > >> >> >> >> >> >------------------------------------------------------------------------- >> >> >This SF.net email is sponsored by the 2008 JavaOne(SM) Conference >> >> >Don't miss this year's exciting event. 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