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How to find inverse of a 608*608 matrix fast?

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I am trying to find the inverse of Q00{5} in the attached c=2_g=1_l=5.mat file. I have tried inv() function as well as backslash function. But this inverse is taking so much time like 20-30 minutes. Is there any faster method to calculate the inverse of this size matrix?


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Accepted Answer

Christine Tobler
Christine Tobler on 1 Jul 2020
The matrices in this file are symbolic, it's very expensive to compute with large arrays of these variables. If you cast it to floating-point numbers, this will be much faster to compute with
>> A = double(Q00{5});
>> tic; inv(A); toc
Elapsed time is 0.009040 seconds.


raina RAJ
raina RAJ on 2 Jul 2020
Thanks this is working. But converting the matrices into double also taking too much time. To aviod this should I convert the entries into double from starting itself (at the time of matrix construction) or is there any other solution avavilable for this?
Christine Tobler
Christine Tobler on 2 Jul 2020
It depends why you originally constructed them as symbolic numbers. If you don't need symbolic computation at all, it will be more efficient to construct in double directly.

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