improve speed --- image matrix replace
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i have a code which has three "for". it's so slow.
if nx=2000,ny=2000. it takes me two minutes to finish replacement.
xfig(nx,ny,3) is a image matrix.
please help me!!
w0=xfig;
nx=length(xfig(:,1,1));%coordinate x
ny=length(xfig(1,:,1));%coordinate y
w1=w0;
for k=1:4
for x=1:nx
for y=1:ny
w1(x,y,:)=w0(mod1(x+y,nx),mod1(x+2*y,ny),:);
end;
end;
%t=1:1:nx;v=1:1:ny;
%w1(t,v,:)=w0(mod1(t+v,nx),mod1(t+2*v,ny),:);
w0=w1;
end;
% if mod(8,4)=0 then it isn't 0, instead of 4
function T=mod1(x,y)
if mod(x,y)==0
T=y;
else
T=mod(x,y);
end
end
1 comentario
Sean de Wolski
el 20 de Mayo de 2013
Have you used the profiler to run your code and identify bottlenecks?
Respuestas (1)
David Sanchez
el 20 de Mayo de 2013
1st: initialize w1
w1 = zeros(nx,ny,3);
The two inner loops do not make use of k, the outer loop index. Why do you have them there? Take them out.
for x=1:nx
for y=1:ny
w1(x,y,:)=w0(mod1(x+y,nx),mod1(x+2*y,ny),:);
end;
end;
what's this for?
for k=1:4
%t=1:1:nx;v=1:1:ny;
%w1(t,v,:)=w0(mod1(t+v,nx),mod1(t+2*v,ny),:);
w0=w1;
end;
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