Speed reduction of 2.1.48 wrt 2.1.36 for structures

[David Bateman]

Working to trying and find out why someones code here ran substantially
slower under the new versions of octave. The problem was isolation to 
the accessing of stuctures within for loops. Consider the code

x.a = 1;
x.b = 1;
xa = x.a;
xb = x.b;
tic; for i=1:10000, y.a = x.a(x.b); endfor; toc
tic; for i=1:10000, ya = xa(xb); endfor; toc

x.a = ones(1,1024);
x.b = 1:1024;
xa = x.a;
xb = x.b;
tic; for i=1:1000, y.a = x.a(x.b); endfor; toc
tic; for i=1:1000, ya = xa(xb); endfor; toc


Under 2.1.36 on my machine I get the results

ans = 0.31809
ans = 0.22774
ans = 0.20027
ans = 0.19229

Under 2.1.48 I get

ans = 0.67814
ans = 0.26059
ans = 0.28205
ans = 0.23896

As can be seen the first test where there is little vectorization, thhe
accessing of the structures is substantially slower under the recent versions
of the code. The tests above were run on the same machine and config
flags (eg math libraries etc)..

Regards
David


-- 
David Bateman                                address@hidden
Motorola CRM                                 +33 1 69 35 25 00 (Ph)
Espace Technologique, Commune de St Aubin    +33 1 69 35 25 01 (Fax)
91193 Gif-Sur-Yvette FRANCE

The information contained in this communication has been classified as: 

[x] General Business Information 
[ ] Motorola Internal Use Only 
[ ] Motorola Confidential Proprietary