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Topic: speeding up assigning values to a matrix
Replies: 7   Last Post: Apr 8, 2013 3:52 AM

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Posts: 77
Registered: 6/6/12
Re: speeding up assigning values to a matrix
Posted: Apr 5, 2013 12:32 PM
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I do not understand what you are saying.
What does it mean "there is a way which is slower than" ? Is it a question for me to find a slower way?
I tried a lot of different operations and I discovered that it is extremely slow to do
A=(mask==num)*255; (1)
(casting or not num to uint8 changes less than 0.1%)

I found it insted to be very fast, acceptably for my scope, to do
A= uint8(mask==num)*uint8(255); (2)

the difference between the (1) and (2) is 300ms for the first one and 15ms for the second one!!!
A factor 20.
Very curious indeed.

That works for now.
(still wondering wether I can use logical indexing to do something like:
aa = (mask==num);
maskC(aa,1)= 250;
and get the best performances of "vectorialized" matlab)

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