how to convert from and to QR compact format?
Posted: Sun Mar 25, 2012 8:31 amHello,
Please note that I am new to LAPACK and fortran.
Can anyone please point me to documentation or functions on how to convert from explicit Q and R to compact LAPACK QR? I would like to make my explicit Q and R to the QR format produced by dgeqrf.
I think I know how to do the other way around, from the compact LAPACK QR format to Q is using dorgqr or dormqr and recovering the R would be using cblas_dtrsm multiplying by the identity, right?
I need this in the context of an iterative algorithm that mutates matrices in different ways and it is very relevant to efficiently update QR by columns and/or row modifications and this is not standard part of LAPACK and therefore the need I have to deal with the different representations.
Many thanks in advance,
Best regards,
Giovanni
Please note that I am new to LAPACK and fortran.
Can anyone please point me to documentation or functions on how to convert from explicit Q and R to compact LAPACK QR? I would like to make my explicit Q and R to the QR format produced by dgeqrf.
I think I know how to do the other way around, from the compact LAPACK QR format to Q is using dorgqr or dormqr and recovering the R would be using cblas_dtrsm multiplying by the identity, right?
I need this in the context of an iterative algorithm that mutates matrices in different ways and it is very relevant to efficiently update QR by columns and/or row modifications and this is not standard part of LAPACK and therefore the need I have to deal with the different representations.
Many thanks in advance,
Best regards,
Giovanni