matlab taking too much time
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Im doing a ray tracing in matlab with this code. It is taking more 6+ hours to complete. Can anyone help
for j=1:sm
for i=1:lns2
m=-1;
P0=SM(j,:);
P1=LNS2(i,:);
OBJ=(P1-F1)/norm(P1-F1);
ILL=(P1-P0)/norm(P1-P0);
OUT=m*(OBJ-Rray1)+ILL;
t=sym('t');
RAY=P1+t*OUT;
EQN=RAY(1)==D2;
t0=solve(EQN,t);
P2=subs(RAY,t,t0);
a1=find(P2(2)<=Y2max);
a2=find(P2(2)>=Y2min);
a3=find(P2(3)<=Z2max);
a4=find(P2(3)>=Z2min);
if a1*a2*a3*a4==1
OBJ=(F2-P2)/norm(F2-P2);
ILL=(P2-P1)/norm(P2-P1);
OUT=m*(OBJ-Rray2)+ILL;
RAY=P2+t*OUT;
EQN=RAY(1)==D3;
t0=solve(EQN,t);
P3=subs(RAY,t,t0);
a1=find(P3(2)<=Ymax);
a2=find(P3(2)>=Ymin);
a3=find(P3(3)<=Zmax);
a4=find(P3(3)>=Zmin);
if a1*a2*a3*a4==1
y=norm(P1-P0)+norm(P2-P1)+norm(P3-P2);
y=sin(y*2*pi);
P3=(round(P3*M))/M;
IY=1+M*(Ymax-P3(2));
IZ=1+M*(Zmax-P3(3));
IMGMTRX(IY,IZ)=IMGMTRX(IY,IZ)+y;
end
end
end
end
采纳的回答
John D'Errico
2016-7-29
0 个投票
Why not learn to use the profile tool? That will tell you where the bottlenecks lie, where you need to work to improve your code.
If I had to guess though, your first obvious problem is in the solve. You are using a symbolic tool to solve a problem (REPEATEDLY!) that is surely solvable using other tools. Or, do the symbolic solve up front, ONCE. That will hopefully give you a simple formula you can then use. At worst, consider a numerical solver.
Symbolic tools tend to be slow. I'm sure there are other problems, but that is the glaring one.
But do you really need the accuracy of a symbolic solve anyway? At the end, it appears you are rounding your results to turn into pixels. Symbolic is wild overkill here.
2 个评论
Gaurav Goyal
2016-7-29
编辑：Gaurav Goyal
2016-7-29
John D'Errico
2016-7-30
The profile tool will slow things down some, making it run longer yet. This makes sense since you are requesting MATLAB to do extra bookkeeping.
So the trick is to reduce the problem size a bit so the profile tool will get its job done in a reasonable time. It will still identify any serious bottleneck. Once you see where a bottleneck lies, then you look to see if there are ways to improve it. And there are ALWAYS lots of way to improve. I am sure I could take virtually anything I've written over the years and find fragments I could do better, at least marginally. MATLAB is continually evolving, as I hope so am I.
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