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Re: Writing efficient normal distribution function (for learning purposes).

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Joshua Maurice <joshuamaurice@gmail.com> writes:
>> So i'd suggest:
>>
>>   g++ -c -o mylib.o -O2 -march=native mylib.cpp
>>   g++ -c -o main.o -O2 -march=native  main.cpp
>>   g++ -o executableneme main.o mylib.o
>
> Why no -O3?
>
> http://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html#Optimize-Options
>
> -O3
>     Optimize yet more. -O3 turns on all optimizations specified by -O2
> and also turns on the -finline-functions, -funswitch-loops, -
> fpredictive-commoning, -fgcse-after-reload, -ftree-vectorize and -fipa-
> cp-clone options.
>
> Function inlining is pretty important for C++.

-O2 does comprehensive inlining as well -- including functions not
 marked "inline" -- using gcc's inlining heuristics, which are quite
 good these days.  [What "-finline-functions" does is act as _every
 function_ were marked "inline" meaning gcc will be more likely to
 inline stuff, even when it doesn't think it's a good idea.]

-O2 is a good default choice if want good optimization, but don't want
to spend a lot of time benchmarking.  -O3 includes optimizations that
may be very expensive at compile-time or may result in excessive code
bloat (and thus can have a negative effect on the icache etc).  -O3
can _sometimes_ help, but it can also sometimes hurt, so it's a good
idea to do some benchmarking to determine which is better.

-Miles

-- 
Cynic, n. A blackguard whose faulty vision sees things as they are, not as
they ought to be. Hence the custom among the Scythians of plucking out a
cynic's eyes to improve his vision.

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Writing efficient normal distribution function (for learning purposes). Luca Cerone <luca.cerone@gmail.com> - 2012-02-17 07:41 -0800
  Re: Writing efficient normal distribution function (for learning purposes). "Asger Joergensen" <Junk@Asger-P.dk> - 2012-02-17 16:45 +0000
    Re: Writing efficient normal distribution function (for learning purposes). lucacerone <luca.cerone@gmail.com> - 2012-02-17 09:36 -0800
      Re: Writing efficient normal distribution function (for learning purposes). "Asger Joergensen" <Junk@Asger-P.dk> - 2012-02-17 17:50 +0000
        Re: Writing efficient normal distribution function (for learning purposes). lucacerone <luca.cerone@gmail.com> - 2012-02-19 01:59 -0800
          Re: Writing efficient normal distribution function (for learning purposes). lucacerone <luca.cerone@gmail.com> - 2012-02-19 02:49 -0800
            Re: Writing efficient normal distribution function (for learning purposes). "Asger Joergensen" <Junk@Asger-P.dk> - 2012-02-19 11:53 +0000
            Re: Writing efficient normal distribution function (for learning purposes). Miles Bader <miles@gnu.org> - 2012-02-19 23:09 +0900
              Re: Writing efficient normal distribution function (for learning purposes). Joshua Maurice <joshuamaurice@gmail.com> - 2012-02-19 13:34 -0800
                Re: Writing efficient normal distribution function (for learning purposes). Marc <marc.glisse@gmail.com> - 2012-02-19 22:10 +0000
                Re: Writing efficient normal distribution function (for learning purposes). Miles Bader <miles@gnu.org> - 2012-02-20 09:14 +0900
                Re: Writing efficient normal distribution function (for learning purposes). Juha Nieminen <nospam@thanks.invalid> - 2012-02-20 10:24 +0000
                Re: Writing efficient normal distribution function (for learning purposes). Miles Bader <miles@gnu.org> - 2012-02-20 19:57 +0900
                Re: Writing efficient normal distribution function (for learning purposes). Dombo <dombo@disposable.invalid> - 2012-02-20 21:07 +0100
                Re: Writing efficient normal distribution function (for learning purposes). Juha Nieminen <nospam@thanks.invalid> - 2012-02-21 08:41 +0000
                Re: Writing efficient normal distribution function (for learning purposes). 88888 Dihedral <dihedral88888@googlemail.com> - 2012-02-21 01:10 -0800
                Re: Writing efficient normal distribution function (for learning purposes). Miles Bader <miles@gnu.org> - 2012-02-20 09:04 +0900
              Re: Writing efficient normal distribution function (for learning purposes). lucacerone <luca.cerone@gmail.com> - 2012-02-20 02:26 -0800
    Re: Writing efficient normal distribution function (for learning purposes). Juha Nieminen <nospam@thanks.invalid> - 2012-02-17 20:42 +0000
      Re: Writing efficient normal distribution function (for learning purposes). "Asger Joergensen" <Junk@Asger-P.dk> - 2012-02-17 22:20 +0000
  Re: Writing efficient normal distribution function (for learning purposes). Juha Nieminen <nospam@thanks.invalid> - 2012-02-17 20:52 +0000
  Re: Writing efficient normal distribution function (for learning purposes). Victor Bazarov <v.bazarov@comcast.invalid> - 2012-02-17 15:57 -0500
  Re: Writing efficient normal distribution function (for learning purposes). Joshua Maurice <joshuamaurice@gmail.com> - 2012-02-17 15:01 -0800
    Re: Writing efficient normal distribution function (for learning purposes). Victor Bazarov <v.bazarov@comcast.invalid> - 2012-02-18 08:44 -0500
      Re: Writing efficient normal distribution function (for learning purposes). Paavo Helde <myfirstname@osa.pri.ee> - 2012-02-18 09:20 -0600
  Re: Writing efficient normal distribution function (for learning purposes). Paavo Helde <myfirstname@osa.pri.ee> - 2012-02-18 09:36 -0600
    Re: Writing efficient normal distribution function (for learning purposes). glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-02-18 20:19 +0000
      Re: Writing efficient normal distribution function (for learning purposes). Miles Bader <miles@gnu.org> - 2012-02-19 10:32 +0900
  Re: Writing efficient normal distribution function (for learning purposes). lucacerone <luca.cerone@gmail.com> - 2012-02-20 02:36 -0800
  Re: Writing efficient normal distribution function (for learning purposes). gwowen <gwowen@gmail.com> - 2012-02-20 06:48 -0800
    Re: Writing efficient normal distribution function (for learning purposes). lucacerone <luca.cerone@gmail.com> - 2012-02-21 04:32 -0800

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