I have a specific line of code:
P2_r = 1 + 0.5*abs(U_O(:,:,ctr) - 0.5) + 0.5*abs(cand - 0.5) - 0.5*abs(U_O(:,:,ctr) - cand);
where U_0 is an array that varries in size from 10's of elements to 100,000+ elements depending on the progression of the parent's code. cand is a single element of U_0, and ctr is simply controlling the 3rd dimension. Now, when U_0 hits a size of approximately 130,000+ elements the computation time of the line of code jumps by 2 to 3 orders of magnitude. This becomes a bottleneck because P2_r is at the core of an optimization routine.
I've read that MATLAB will call LAPACK/BLAS when it is determined the overhead is worth it. If MATLAB is truly calling a different math library, is it possible to control the criteria it uses to determine the switching point? Or redirect LAPACK/BLAS calls back to MATLAB's default algorithms? multiply() and abs() are built-in functions, so I do not have access to the source code.
Thanks for your help!
The above figure depicts the jump in computation time observed for arrays of varrying dimensions (columns) around 130,000+ elements. The specific line of code is the bottleneck of a larger rountine that computes the following quantity known as discrepancy:
I have also attached a profile of the discrepancy routine that shows P2_r as consuming the largest fraction of computation time