Re: [OctDev] Help making padarray.m quicker

[Paul K. <pki...@us...>]

On Aug 9, 2004, at 10:39 PM, Josep Mon=E9s i Teixidor wrote:

> On dt, 2004-08-10 at 04:31, Josep Mon=E9s i Teixidor wrote:
>
>> Or perhaps cat is quick?
>
> If tried a little test to pad "manually" a 1000*1000 matrix with 50
> zeros (as if we used 'both').
>
> octave:10> A=3Dones(1000,1000); t=3Dtime(); for i=3D1:10;
> =
B=3Dcat(2,zeros(1100,50),cat(1,zeros(50,1000),A,zeros(50,1000)),zeros(110=20=

> 0,50)); endfor; time()-t
> ans =3D 5.5180
>
> octave:11> A=3Dones(1000,1000); t=3Dtime(); for i=3D1:10; =
B=3Dzeros(1100,1100);
> B(51:1050,51:1050)=3DA; endfor; time()-t
> ans =3D 5.4502
>
> What do you think of these times?

2.1.55 on OS X:

octave:50> n=3D800; A=3Dones(n,n);
octave:51> tic; B=3Dzeros(n+100,n+100); B(51:n+50,51:n+50)=3DA; toc
ans =3D 0.29751
octave:52> tic; =20
B=3Dcat(2,zeros(n+100,50),cat(1,zeros(50,n),A,zeros(50,n)),zeros(n+100,50)=
=20
); toc
ans =3D 3.0635

2.1.57 on Debian, gcc 3.3.3

octave:26> n=3D800; A=3Dones(n,n);
octave:27> tic; B=3Dzeros(n+100,n+100); B(51:n+50,51:n+50)=3DA; toc
ans =3D 0.30018
octave:28> tic; =20
B=3Dcat(2,zeros(n+100,50),cat(1,zeros(50,n),A,zeros(50,n)),zeros(n+100,50)=
=20
); toc
ans =3D 0.33685


- Paul=