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# Harry Commin

### Imperial College London

12 total contributions since 2010

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matrix 9x9 with duplicate values
To extract only the upper triangular numbers into a column vector, you could use: Aupper = A(triu(ones(size(A)))==1); I ...

3 years ago | 0

Responded

Re: Efficiently computing large numbers of vector norms
I copied and pasted your code (but had to remove the *5 on the dimensions to avoid Out of Memory errors) and KronProd performs s...

4 years ago | 4564 views

Posted

Reducing memory requirements for tiled matrices
Yes, using multiple loops was actually my starting point, but then I removed the loops in an attempt to speed up execution. This...

4 years ago | 3469 views

Responded

Re: Efficiently computing large numbers of vector norms
Thanks, I had no idea that ctranspose would be such an important issue. I'll look back at my problem now and will try to convert...

4 years ago | 4564 views

Posted

Reducing memory requirements for tiled matrices
I need to perform element-by-element multiplication between two "tiled" matrices (i.e. where relatively few unique values are re...

4 years ago | 3469 views

Responded

Re: Efficiently computing large numbers of vector norms
I cannot repeat your test, as I get an "Out of Memory" error. Furthermore, I require that A1 and A2 change on each iteration. Th...

4 years ago | 4564 views

Responded

Re: Efficiently computing large numbers of vector norms
For my tests, I had: N1 = 3; N2 = 4; Q1 = 180; Q2 = 63; If I increase N1 and/or N2, the improvement (due to KronProd) decrease...

4 years ago | 4564 views

Responded

Re: Efficiently computing large numbers of vector norms
Sorry, please disregard my last post. I repeated for 1000 iterations instead of 1 and I now get: My original loop: 29.3665 secs...

4 years ago | 4564 views

Responded

Re: Efficiently computing large numbers of vector norms
Thanks very much for these suggestions. Perhaps I am doing something wrong -- while I am getting the correct results numerically...

4 years ago | 4564 views

Responded

Re: Efficiently computing large numbers of vector norms
I should add that X is always square complex.

4 years ago | 4564 views

Posted

Efficiently computing large numbers of vector norms
I am frequently faced with problems where I need to find the norm (squared) of row vectors having the following structure: A(:,...

4 years ago | 4564 views

Responded

Re: find nearest,closest value
This is brilliant code. Is there a simple way to extend it for comparison of vectors? That is, given two matrices, A and B (whe...

6 years ago | 72121 views