[OctDev] Help making padarray.m quicker

[Josep i T. <jm...@pu...>]

Hello!

I've tried to recode padarray.m to preallocate array and then assign
padding values instead of using cat everywhere expecting a speed
improvement.

The recoded version is attached. The results of the tests below (using a
4D test array) show that original version is quicker.

I didn't expect that at all, can anybody have a look at the attached
code to see if there's something very wrong that could be slowing thing
down?

Or perhaps cat is quick?

Thanks

----->%------------>%--------
Using NEW padarray.m:

octave:1> A=3Dones(30,30,30,30); t=3Dtime(); for i=3D1:10;
B=3Dpadarray(A,[2,2,2,2]); endfor; time()-t
ans =3D 32.391
octave:2> A=3Dones(30,30,30,30); t=3Dtime(); for i=3D1:10;
B=3Dpadarray(A,[2,2,2,2],10); endfor; time()-t
ans =3D 34.200
octave:3> A=3Dones(30,30,30,30); t=3Dtime(); for i=3D1:10;
B=3Dpadarray(A,[2,2,2,2],'circular'); endfor; time()-t
ans =3D 74.152
octave:4> A=3Dones(30,30,30,30); t=3Dtime(); for i=3D1:10;
B=3Dpadarray(A,[2,2,2,2],'replicate'); endfor; time()-t
ans =3D 73.749
octave:5> A=3Dones(30,30,30,30); t=3Dtime(); for i=3D1:10;
B=3Dpadarray(A,[2,2,2,2],'symmetric'); endfor; time()-t
ans =3D 74.707



Using OLD pararray.m:
octave:1> A=3Dones(30,30,30,30); t=3Dtime(); for i=3D1:10;
B=3Dpadarray(A,[2,2,2,2]); endfor; time()-t
ans =3D 13.106
octave:2> A=3Dones(30,30,30,30); t=3Dtime(); for i=3D1:10;
B=3Dpadarray(A,[2,2,2,2],10); endfor; time()-t
ans =3D 13.596
octave:3> A=3Dones(30,30,30,30); t=3Dtime(); for i=3D1:10;
B=3Dpadarray(A,[2,2,2,2],'circular'); endfor; time()-t
ans =3D 44.399

replicate segfaulted (I believe CVS Octave should be able to handle it,
I've found problems when using cat on ND arrays).

octave:1> A=3Dones(30,30,30,30); t=3Dtime(); for i=3D1:10;
B=3Dpadarray(A,[2,2,2,2],'symmetric'); endfor; time()-t
ans =3D 44.495
----->%------------>%--------


--=20
Josep Mon=E9s i Teixidor
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