# Large sparse matrix LU decomposition

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chan yeoung woo on 29 Jun 2021
Commented: Christine Tobler on 30 Jun 2021
KK matrix is 305461 x 305461 sparse matrix
1)An out of memory error appears when running LU
is there a solution?
[L,U] = lu(KK)
2)What should I do to see the LU when using dk?
dK= decomposition(KK,'lu')
[L,U]= lu(dK) <== error : Error occurred while using:lu Invalid data type. The first argument must be double or single

Christine Tobler on 29 Jun 2021
If the call to lu runs out of memory, but the call to decomposition(__, 'lu') doesn't, likely the reason is that decomposition uses the five-output syntax of LU, which is much more efficient. You could try calling that syntax directly.
Decomposition doesn't support extracting the factors directly, just solving a linear system based on those factors which are internally stored in a quite different format.
##### 2 CommentsShowHide 1 older comment
Christine Tobler on 30 Jun 2021
It depends what you want to do with L and U. The five-output syntax returns L, U, and additional permutation and scaling matrices, perhaps you can adapt your usage of L and U to this case?

R2020b

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