LAPACK/ScaLAPACK Development

Hello,

All LU (and also QR with column pivoting) related LAPACK functions has as an argument an array IPIV that stores the indices of row (columns for QR) permutations. In LAPACKE, are the indices of this array 0-based or 1-based, as in Fortran?, i.e., an index for the first row , is stored as 0 or as 1?

Thanks

The address of the pointer given will always be the first memory address.
So if you give ipiv as argument of the function

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info = LAPACKE_dgesv( LAPACK_ROW_MAJOR, n, nrhs, A, lda, ipiv, b, ldb );


with iliv defined as:

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      lapack_int *ipiv;
      ipiv = (lapack_int *)malloc(n*sizeof(lapack_int)) ;


Your IPIV values are going to be store from ipiv[0] to ipiv[n-1]

Hope it helps
Julie

Sorry, probably my explanation was not so clear. I mean the indices stored in IPIV as the rows to permute, i.e, it the second row is involved in one permutation, are the value 2 or 1 stored in IPIV? Using Fortran LAPACK, number 2 is stored. And using LAPACKE, 2 or 1?

Thanks

IPIV is based on row indexex ranging from 1 to N whether you use the LAPACK Fortran Interface or the LAPACKE C Interface. Cheers, Julien.

if the second row is involved in one permutation, are the value 2 or 1 stored in IPIV? Using Fortran LAPACK, number 2 is stored. And using LAPACKE, 2 or 1?

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