Re: plans for single-precision support?

[Jaroslav Hajek]

On Wed, Sep 1, 2010 at 8:23 AM, Tim Rueth <address@hidden> wrote:
>
>> -----Original Message-----
>> From: Tatsuro MATSUOKA [mailto:address@hidden
>> Sent: Tuesday, August 31, 2010 9:40 PM
>> To: address@hidden; 'Martin Helm'; address@hidden
>> Subject: RE: plans for single-precision support?
>>
>> Hello
>>
>> It seems that octave-3.2.3/MinGW32 supports the 'single' function.
>>
>>
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>> warning: mark_as_command is obsolete and will be removed from
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>> octave-3.2.3.exe:1:C:\Programs\Octave\3.2.3_gcc4.4.0\bin
>> > help single
>> `single' is a built-in function
>>
>>  -- Built-in Function:  single (X)
>>      Convert X to single precision type.
>>
>>      See also: double
>>
>>
>>
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>> octave-3.2.3.exe:11:C:\Programs\Octave\3.2.3_gcc4.4.0\bin
>> > x=0.1
>> x =  0.100000000000000
>> octave-3.2.3.exe:12:C:\Programs\Octave\3.2.3_gcc4.4.0\bin
>> > y=single(x)
>> y =  0.100000001490116
>> octave-3.2.3.exe:13:C:\Programs\Octave\3.2.3_gcc4.4.0\bin
>> > whos
>> Variables in the current scope:
>>
>>   Attr Name        Size                     Bytes  Class
>>   ==== ====        ====                     =====  =====
>>        x           1x1                          8  double
>>        y           1x1                          4  single
>>
>> Total is 2 elements using 12 bytes
>>
>> **********************************************************************
>>
>> If you want to install octave-3.2.4/mingw32, please read
>> carefully the below, (The oct2mat issue should be treated in
>> case installing the whole octave-forge package.)
>>
>> http://wiki.octave.org/wiki.pl?OctaveForWindows
>>
>> Regards
>>
>> Tatsuro
>>
>> --- Tim Rueth wrote:
>>
>> > Oh, I'm still running 3.2.3 (Vista).  I should upgrade to
>> 3.2.4 then.
>> > I'm running into memory problems, and I'm hoping that if I
>> change some
>> > of my matrices from double to single I can cut the memory
>> requirements way down.
>> >
>> > --Tim
>> >
>> >
>> > > -----Original Message-----
>> > > From: Martin Helm [mailto:address@hidden
>> > > Sent: Tuesday, August 31, 2010 3:20 PM
>> > > To: address@hidden; address@hidden
>> > > Subject: Re: plans for single-precision support?
>> > >
>> > > Am Dienstag, 31. August 2010, 23:26:47 schrieb Tim Rueth:
>> > > > Does anyone know when single-precision data types,
>> i.e., single(),
>> > > > will be supported?
>> > > >
>> > > > --Tim
>> > >
>> > > Maybe I do not understand your question, single() is available in
>> > > octave 3.2.4.
>
> Oh, you're right.  I read in the Octave Manual for single() that:
>
>        Note: this function currently returns its argument converted to
> double precision
>        because Octave does not yet have a single-precision numeric data
> type.
>
> But I tried your test case and sure enough, it works, thanks.
>
> Since it appears Octave defaults to double, I'm still having to initially
> allocate memory for twice the space that I need, then I give back half.  I'm
> using ndgrid() to create numerous very large matrices.  Is there a way to
> invoke ndgrid() so that it just creates single-precision matrices without
> recasting them from double back to single?
>

Just pass it single precision arguments.

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