From help-octave-request at bevo dot che dot wisc dot edu  Mon Jan 31 08:35:12 2000
Subject: efficiency
From: Daniel Heiserer <Daniel dot Heiserer at bmw dot de>
To: "help-octave at bevo dot che dot wisc dot edu" <help-octave@bevo.che.wisc.edu>
Date: Mon, 31 Jan 2000 15:34:33 +0100

Hi,


Assume I have a few hundred matrices:

k_0004711
k_0004712
.........


And I want to loop through a subset of them
with a certain function:

like:

 a=myfunc(b,c,K__00047[1-5])   # in shell regexps .... ;-)
	call for each matrix

What is better/more efficient:

1) copying the data via a temporary variable

for jj=1:5
	tmp=eval(sprintf('k_%7d',47*1000+jj));
	a=myfunc(b,c,tmp);
end
% Which probably means copying data in core each time .......
% for big loops not nice .......
or 

2) putting the eval above all:

for jj=1:5
	eval(sprintf('a=myfunc(a,b,K_%7d)',47*1000+jj));
end
% no idea about what is really done here....

or 

3) put all the crap in ONE Monster array, store the indices somewhere
and do it like this and making all the code realy ugly .......

a=myfunc(a,b,K_monster,K_indices);
% is here any data copied?
% and does it only make the code unreadible

4) or a really good idea :-), which I don't have right now ......


Thanks Daniel



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