Re: Finding out the optimizations used by Octave

[Jaroslav Hajek]

On Sat, Jan 23, 2010 at 4:04 PM, George <address@hidden> wrote:
> On 1/23/10, Jaroslav Hajek <address@hidden> wrote:
>> On Sat, Jan 23, 2010 at 4:51 AM, George <address@hidden> wrote:
>>> Is there an Octave command to find which CPU optimizations are in use?
>>
>> I'm not sure if that's what you mean, but the CPU instruction set used
>> is usually fixed at the time of compilation. Typically it's the FPU
>> instructions by default on 32-bit machines, and SSE instructions on
>> 64-bit machines. It also heavily depends on the compiler and flags
>> used. Some compilers, like Intel C++, can use a runtime dispatch to
>> different code paths optimized for different platforms (yes and it's
>> Intel-centric). To find out the compiler and flags used, you can do
>> (in Octave):
>>
>> octave:1> octave_config_info ("CXX")
>> ans = g++
>> octave:2> octave_config_info ("CXXFLAGS")
>> ans = -O3 -march=native
>>
>
> I remember installing Octave on Windows, and it would ask me which
> optimizations I wanted to use. I remember it crashing if I used SSE3.
> I suppose the selection was just about the Atlas libraries? I think
> so.
>
> But right now I'm using Octave on Debian, and I installed Octave from
> the Debian repository. I get this:
>
> octave:1> octave_config_info ("CXXFLAGS")
> ans = -O2 -g
> octave:2> octave_config_info ("CXX")
> ans = g++
>
> The -g option generates a debug build, right? Why would Debian
> distribute a debug build?
>

Good question. These flags are default, so probably they just didn't
change them. I'd suggest you ask the package maintainer.


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