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Simple Question about Optimization of Nested IF-FOR loops

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Mohsen
Mohsen 2013-6-17
关闭： MATLAB Answer Bot 2021-8-20
Does any one know how to optimize this code so that it runs faster:
for i=1:iNZ;
if iPointsinSlice>0;
for m=1:iNX;
for l=1:iNY;
if SliceMaskUr(m,l)==1;
DoseCubeU(m+(l-1)*iNX+i*iNX*iNY)=100*SumDose(m,l,i)/RX_Dose;
end
end
end
end
end
Your help is much appreciated! Thanks a lot!

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回答（5 个）

Roger Stafford
Roger Stafford 2013-6-17
Is 'iPointsinSlice' a scalar? If so and if it is not positive, nothing will happen here.
Next, don't you mean "m+(l-1)*iNX+(i-1)*iNX*iNY" as the index to 'DoseCubeU'? As it stands it will vary from 1+iNX*iNY to iNX*iNY*iNZ+iNX*iNY. Assuming my guess is correct, do this:
if iPointsinSlice > 0
t = repmat(SliceMaskUr==1,1,1,iNZ);
DoseCubeU(t) = (100/RX_Dose)*SumDose(t);
end
In case 'iPointsinSlice' is not a scalar you will have to correct your code before we can see how to handle it.
  1 个评论
Mohsen
Mohsen 2013-6-17
'iPointsinSlice' is a scalar. "m+(l-1)*iNX+(i-1)*iNX*iNY" is used as the index to 'DoseCubeU. But your code gives the error that REPMAT has too many arguments. How should I fix it?
Roger Stafford
Roger Stafford 2013-6-17
Sorry! It should have been:
t = repmat(SliceMaskUr==1,[1,1,iNZ]);
  1 个评论
Mohsen
Mohsen 2013-6-18
I changed
DoseCubeU(m+(l-1)*iNX+i*iNY*iNX)=100*SumDose(m,l,i)/RX_Dose;
to
DoseCubeU(double(m)+double((l-1))*double(iNX)+double((i-1))*double(iNY)*double(iNX))=100*SumDose(m,l,i)/RX_Dose;
Otherwise the indexing will not be correct. For example, iNX*iNY*iNZ (which is 120*120*11) becomes equal to 65535 (which is wrong). We should write it as double(iNX)*double(iNY)*double(iNZ) in order to get the correct results (ie. 158400).
By making this change, both the indexing (the initial) method and the subscription method (below) give the same results. But these results are different than any of the other proposed methods.
So, how can I optimize:
for i=1:iNZ;
if iPointsinSlice>0;
for m=1:iNX;
for l=1:iNY;
if SliceMaskUr(m,l)==1;
DoseCubeU(m,l,i)=100*SumDose(m,l,i)/RX_Dose;
end
end
end
end
end
Mohsen
Mohsen 2013-6-17
This code doesn't give me the same result as my initial code. Please note that the purpose of "m+(l-1)*iNX+i*iNX*iNY" is to reshape the SumDose array which is (iNX by iNY by iNZ) to a one dimensional array (1 by iNX*iNY*iNZ).
I tried also
if SliceMaskUr==1;
DoseCubeU= reshape(SumDose,1,[iNX iNY iNZ])*(100/RX_Dose);
end
but it didn't work neither...
Any insight?
  4 个评论
显示 2更早的评论
Mohsen
Mohsen 2013-6-18
I think that the function poly2mask is in charge of these discrepancies. Any idea why? Here is the entire code:
iNNX=double(iNX);
iNNY=double(iNY);
for i=1:iNZ;
iPointsinSlice=1;
for j=1:iNCUr;
if UrContourZ(j)==ZSlice(i);
iPointsinSlice = iPointsinSlice+1;
UrPointX(iPointsinSlice-1)=1 + (UrContourX(j)-Offset(1,1));
UrPointY(iPointsinSlice-1)=1 + (UrContourY(j)-Offset(2,1));
end
end
if iPointsinSlice>0;
indx=round(iPointsinSlice);
indy=round(iPointsinSlice);
indx(1:iPointsinSlice-1)=UrPointX(1:iPointsinSlice-1)/DresX;
indy(1:iPointsinSlice-1)=UrPointY(1:iPointsinSlice-1)/DresY;
SliceMaskUr = poly2mask(indx,indy,iNNX,iNNY);
for m=1:iNX;
for l=1:iNY;
if SliceMaskUr(m,l)==1;
DoseCubeU(m+(l-1)*iNX+(i-1)*iNY*iNX)=100*SumDose(m,l,i)/RX_Dose;
end
end
end
end
end
Your help is much appreciated! :)
Mohsen
Mohsen 2013-6-18
I changed
DoseCubeU(m+(l-1)*iNX+i*iNY*iNX)=100*SumDose(m,l,i)/RX_Dose;
to
DoseCubeU(double(m)+double((l-1))*double(iNX)+double((i-1))*double(iNY)*double(iNX))=100*SumDose(m,l,i)/RX_Dose;
Otherwise the indexing will not be correct. For example, iNX*iNY*iNZ (which is 120*120*11) becomes equal to 65535 (which is wrong). We should write it as double(iNX)*double(iNY)*double(iNZ) in order to get the correct results (ie. 158400).
By making this change, both the indexing (the initial) method and the subscription method (below) give the same results. But these results are different than any of the other proposed methods.
So, how can I optimize:
for i=1:iNZ;
if iPointsinSlice>0;
for m=1:iNX;
for l=1:iNY;
if SliceMaskUr(m,l)==1;
DoseCubeU(m,l,i)=100*SumDose(m,l,i)/RX_Dose;
end
end
end
end
end
Andrei Bobrov
Andrei Bobrov 2013-6-18
编辑：Andrei Bobrov 2013-6-19
DoseCubeU = bsxfun(@times,100*SumDose/RX,SliceMaskUr==1);
ADD
s = SliceMaskUr(end:-1:1,end:-1:1);
tt = cumsum(cumsum(s),2);
t1 = flipud(any(tt,2));
t2 = fliplr(any(tt));
DoseCubeU = bsxfun(@times,100*SumDose(t1,t2,:)/RX_Dose,SliceMaskUr(t1,t2));
  4 个评论
显示 2更早的评论
Mohsen
Mohsen 2013-6-18
I changed
DoseCubeU(m+(l-1)*iNX+i*iNY*iNX)=100*SumDose(m,l,i)/RX_Dose;
to
DoseCubeU(double(m)+double((l-1))*double(iNX)+double((i-1))*double(iNY)*double(iNX))=100*SumDose(m,l,i)/RX_Dose;
Otherwise the indexing will not be correct. For example, iNX*iNY*iNZ (which is 120*120*11) becomes equal to 65535 (which is wrong). We should write it as double(iNX)*double(iNY)*double(iNZ) in order to get the correct results (ie. 158400).
By making this change, both the indexing (the initial) method and the subscription method (below) give the same results. But these results are different than any of the other proposed methods.
So, how can I optimize:
for i=1:iNZ;
if iPointsinSlice>0;
for m=1:iNX;
for l=1:iNY;
if SliceMaskUr(m,l)==1;
DoseCubeU(m,l,i)=100*SumDose(m,l,i)/RX_Dose;
end
end
end
end
end
Iain
Iain 2013-6-18
Try:
DoseCubeU(NY,NX,NZ) = 0; % or any suitable initialisation
if iPointsinSlice>0;
DoseCubeU(SliceMaskUr(m,l)==1,:) = 100*SumDose(SliceMaskUr(m,l)==1,:);
end
  2 个评论
Mohsen
Mohsen 2013-6-18
This gives me a different answer than all the other four methods!
Mohsen
Mohsen 2013-6-18
I changed
DoseCubeU(m+(l-1)*iNX+i*iNY*iNX)=100*SumDose(m,l,i)/RX_Dose;
to
DoseCubeU(double(m)+double((l-1))*double(iNX)+double((i-1))*double(iNY)*double(iNX))=100*SumDose(m,l,i)/RX_Dose;
Otherwise the indexing will not be correct. For example, iNX*iNY*iNZ (which is 120*120*11) becomes equal to 65535 (which is wrong). We should write it as double(iNX)*double(iNY)*double(iNZ) in order to get the correct results (ie. 158400).
By making this change, both the indexing (the initial) method and the subscription method (below) give the same results. But these results are different than any of the other proposed methods.
So, how can I optimize:
for i=1:iNZ;
if iPointsinSlice>0;
for m=1:iNX;
for l=1:iNY;
if SliceMaskUr(m,l)==1;
DoseCubeU(m,l,i)=100*SumDose(m,l,i)/RX_Dose;
end
end
end
end
end

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