Re: Performance optimization (allocation inside a for loop)

[Jaroslav Hajek]

On Sat, Apr 4, 2009 at 1:28 PM, r <address@hidden> wrote:
> On Sat, Apr 4, 2009 at 7:47 AM, Jaroslav Hajek <address@hidden> wrote:
>>
>> I gave the idea a second thought - maybe it has some merits. Sometimes
>> you really want to use an array as a stack in Octave to avoid going
>> through a loop twice, so Octave can try to optimize such usage.
>
> Thank you for this work. BTW, I've checked that Matlab 2008 doesn't
> indeed optimize such scenario. I'm sorry for the unfair judgement.
>
>> Since the existing shallow slicing mechanism is reused, no extra data
>> is introduced.
> [...]
>> a final question: maybe the maximum over-allocation size should be 
>> configurable?
>
> If I understand correctly that this optimization doesn't take any
> additional memory comparing to the current version, I wouldn't bother
> adding more configuration options.
>
> I tried to give it a try but then I encountered an error when building Octave:
>
> make[3]: Entering directory
> `/home/r/Installation/octave/hg_20090404/octave/libcruft/misc'
> gcc -c -I/usr/include/freetype2 -fPIC -I. -I../.. -I../../liboctave
> -I../../src -I../../libcruft/misc -DHAVE_CONFIG_H -mieee-fp -Wall -W
> -Wshadow -g   -DDP machar.c -o pic/machar.o
> machar.c:2:20: error: config.h: No such file or directory
> In file included from f77-fcn.h:27,
>                 from machar.c:8:
> quit.h:63: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’
> before ‘extern’
> quit.h:65: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’
> before ‘extern’
> quit.h:67: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’
> before ‘extern’
> quit.h:69: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’
> before ‘extern’
> quit.h:71: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’
> before ‘extern’
> quit.h:73: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’
> before ‘extern’
> quit.h:94: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’
> before ‘extern’
> quit.h:101: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’
> before ‘extern’
> quit.h:103: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’
> before ‘extern’
> quit.h:105: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’
> before ‘extern’
> quit.h:107: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’
> before ‘extern’
> quit.h:109: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’
> before ‘extern’
> quit.h:111: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’
> before ‘extern’
> quit.h:113: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’
> before ‘extern’
> quit.h:115: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’
> before ‘extern’
> In file included from machar.c:8:
> f77-fcn.h:79: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’
> before ‘extern’
> f77-fcn.h:222: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’
> before ‘int’
> machar.c:380: error: ‘F77_FUNC’ declared as function returning a function
> machar.c: In function ‘F77_FUNC’:
> machar.c:380: warning: type of ‘machar’ defaults to ‘int’
> machar.c:380: warning: type of ‘MACHAR’ defaults to ‘int’
> machar.c:398: error: ‘eps’ undeclared (first use in this function)
> machar.c:398: error: (Each undeclared identifier is reported only once
> machar.c:398: error: for each function it appears in.)
> machar.c:398: error: ‘epsneg’ undeclared (first use in this function)
> machar.c:398: error: ‘xmin’ undeclared (first use in this function)
> machar.c:398: error: ‘xmax’ undeclared (first use in this function)
> machar.c:401: error: ‘log10_ibeta’ undeclared (first use in this function)
> machar.c: At top level:
> machar.c:380: warning: unused parameter ‘machar’
> machar.c:380: warning: unused parameter ‘MACHAR’
> make[3]: *** [pic/machar.o] Error 1
>
> I guess, this must be some kind of a configuration problem, but where?
>
> $ hg clone http://www.octave.org/hg/octave
> $ patch -p1 << ../stack.diff
> $ autoconf
> $ configure
> $ make
>
> Regards,
>
> -r.
>
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>

try

hg clone http://www.octave.org/hg/octave
cd octave
hg import ../stack.diff
./autogen.sh
./configure CXXFLAGS="-O2" (avoiding -g means a faster build)
make (-j2 on dual core)

regards

-- 
RNDr. Jaroslav Hajek
computing expert & GNU Octave developer
Aeronautical Research and Test Institute (VZLU)
Prague, Czech Republic
url: www.highegg.matfyz.cz