## A problem with LU (culaSgetrf)

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**1**of**1**### A problem with LU (culaSgetrf)

Hi!

Can someone explain to me why culaSgetrf doesn't factorize some matrices, for example a square 5x5 matrix filled with numbers 0..24, I get data error. Matlab, which uses LAPACK can handle such matrices. Is it a bug in CULA? If not, it should be pointed out in the manuals.

Can someone explain to me why culaSgetrf doesn't factorize some matrices, for example a square 5x5 matrix filled with numbers 0..24, I get data error. Matlab, which uses LAPACK can handle such matrices. Is it a bug in CULA? If not, it should be pointed out in the manuals.

- LaChupacabra
**Posts:**2**Joined:**Tue Jan 12, 2010 1:23 am

### Re:A problem with LU (culaSgetrf)

We report the error exactly as LAPACK/MKL does - it in defined as an error condition for a matrix to be singular to the getrf routine, and we report it accordingly as a culaDataError. Matlab actually receives this error and disregards it. (Note that the Matlab inv() operator correctly reports it as singular.)

It's worth noting that the L*U*P can still be used to reconstruct A, but you can't solve a system because you will be forced to divide by zero.

I see your point though. LAPACK still provides the factorization, even if singular. CULA 1.2 will include this, as per your finding.

Thanks for the report,

John

It's worth noting that the L*U*P can still be used to reconstruct A, but you can't solve a system because you will be forced to divide by zero.

I see your point though. LAPACK still provides the factorization, even if singular. CULA 1.2 will include this, as per your finding.

Thanks for the report,

John

- john
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**Posts:**587**Joined:**Thu Jul 23, 2009 2:31 pm

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