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How to improve performance of code ?

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yogesh jain
yogesh jain 2016-2-26
评论： Steven Lord 2016-2-29
Hello all, I am using this code for getting the data point coordinates among defined vertices .
ver = vertice; % nX3 matrix
ver=ceil(ver);
tess=delaunay(ver);
mn_x=min(ver(:,1));
mx_x=max(ver(:,1));
mn_y=min(ver(:,2));
mx_y=max(ver(:,2));
mn_z=min(ver(:,3));
mx_z=max(ver(:,3));
[X,Y,Z]=ndgrid(mn_x:0.8:mx_x , mn_y:0.8:mx_y , mn_z:0.8:mx_z);
sz=size(X);
P=ones(sz(1)*sz(2)*sz(3),3);
for i=1:sz(1)*sz(2)*sz(3)
P(i,1)=X(i);
P(i,2)=Y(i);
P(i,3)=Z(i);
end
pts=zeros(size(P));
for j=1:length(P)
t=tsearchn(ver,tess,P(j,:));
isin=~isnan(t);
if isin ==1
pts(j,:)=P(j,:);
end
end
It works fine but takes a lot time to calculate. How to improve the performance of code ? Thank you :)
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Jan
Jan 2016-2-29
@yogesh jain: It matters if you are talking about day or micro-seconds. n might be 1e3 or 1e10, so please be specific and do not let us guess the details.
yogesh jain
yogesh jain 2016-2-29
for the value of n=about 100 , it takes 50-55 seconds .

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采纳的回答

Jan
Jan 2016-2-29
Please use the profile to find the bottleneck of the code. Some parts are easy to accelerate, but this does not really help, if they take 1% of the total time. E.g.:
P=ones(sz(1)*sz(2)*sz(3),3);
for i=1:sz(1)*sz(2)*sz(3)
P(i,1)=X(i);
P(i,2)=Y(i);
P(i,3)=Z(i);
end
Faster:
P = [X(:), Y(:), Z(:)];
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yogesh jain
yogesh jain 2016-2-29
Yes Mr. Jan "tsearchn" consumes the most time and it is obtaining convexhull in each iteration. thank you
Steven Lord
Steven Lord 2016-2-29
As Jan suggested, rather than calling TSEARCHN multiple times with one row at a time call it with a matrix as the third input and perform all your searches at once. Then check which of the points are outside the convex hull and which are inside and process each group appropriately.

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