topic Incomplete LU Factorization - how to extract L and U ? in Intel® oneAPI Math Kernel Library https://community.intel.com/t5/Intel-oneAPI-Math-Kernel-Library/Incomplete-LU-Factorization-how-to-extract-L-and-U/m-p/830341#M5490 Dear MKL-experts,<BR /><BR />I'd like to use the ilu0 factorization as a preconditioner for a GPU based solver. In order to do so I have to explicitly get the L and the U matrix from the B matrix that is returned by dcsrilu0.<BR /><BR />Can you think of a simple way to do this or is there even a tool in the MKL for this?<BR /><BR />Thanks in advance!<BR /><BR />Cheers,<BR /><BR />Stefan Sun, 15 Jan 2012 20:33:17 GMT sps4 2012-01-15T20:33:17Z Incomplete LU Factorization - how to extract L and U ? https://community.intel.com/t5/Intel-oneAPI-Math-Kernel-Library/Incomplete-LU-Factorization-how-to-extract-L-and-U/m-p/830341#M5490 Dear MKL-experts,<BR /><BR />I'd like to use the ilu0 factorization as a preconditioner for a GPU based solver. In order to do so I have to explicitly get the L and the U matrix from the B matrix that is returned by dcsrilu0.<BR /><BR />Can you think of a simple way to do this or is there even a tool in the MKL for this?<BR /><BR />Thanks in advance!<BR /><BR />Cheers,<BR /><BR />Stefan Sun, 15 Jan 2012 20:33:17 GMT https://community.intel.com/t5/Intel-oneAPI-Math-Kernel-Library/Incomplete-LU-Factorization-how-to-extract-L-and-U/m-p/830341#M5490 sps4 2012-01-15T20:33:17Z Incomplete LU Factorization - how to extract L and U ? https://community.intel.com/t5/Intel-oneAPI-Math-Kernel-Library/Incomplete-LU-Factorization-how-to-extract-L-and-U/m-p/830342#M5491 Hi,<DIV>In example nameddcsrilu0_exampl1.c you can find way how to use matrix obtained by ILU0 as preconditioner. There is no way to get the L and U matrix from matrix B but you can multiply them on vector using SparseBlas functionality.</DIV><DIV>With best regards,</DIV><DIV>Alexander Kalinkin</DIV> Mon, 16 Jan 2012 03:58:37 GMT https://community.intel.com/t5/Intel-oneAPI-Math-Kernel-Library/Incomplete-LU-Factorization-how-to-extract-L-and-U/m-p/830342#M5491 Alexander_K_Intel2 2012-01-16T03:58:37Z Incomplete LU Factorization - how to extract L and U ? https://community.intel.com/t5/Intel-oneAPI-Math-Kernel-Library/Incomplete-LU-Factorization-how-to-extract-L-and-U/m-p/830343#M5492 Hi Alexander,<BR /><BR />thank you very much for your very fast answer. I have to extract L and U as I'm using a GPU based backsolve method (not the MKL mkl_cspblas_dcsrtrsv).<BR /><BR />There have to be a way to do this. Maybe I can perform a matrix-matrix multiplication with the identity matrix, but use only the lower or upper part in the multiplication? For that I need to routines:<BR />1. Initilialize a sparse identitiy matrix. Is that possible with MKL?<BR />2. Perform a matrix-matrix multiplication, but only use the L or U part (like mkl_cspblas_dcsrtrsv does it). Is there a suitable routine in the MKL?<BR /><BR />Thanks in advance!<BR /><BR />Cheers,<BR /><BR />Stefan<BR /> Mon, 16 Jan 2012 11:03:42 GMT https://community.intel.com/t5/Intel-oneAPI-Math-Kernel-Library/Incomplete-LU-Factorization-how-to-extract-L-and-U/m-p/830343#M5492 sps4 2012-01-16T11:03:42Z Incomplete LU Factorization - how to extract L and U ? https://community.intel.com/t5/Intel-oneAPI-Math-Kernel-Library/Incomplete-LU-Factorization-how-to-extract-L-and-U/m-p/830344#M5493 <P>Hi,</P> <P>From my point of view you can malloc 2 set of 3 arrays (ia,ja, a) for matrices L and U correspondently and convert data from matrix B to these matrices using simple loop. Lower part of matrix B correspond to matrix L and upper correspond to matrix U.</P><P>With best regards,</P><P>Alexander Kalinkin</P><BR /> Wed, 18 Jan 2012 03:49:02 GMT https://community.intel.com/t5/Intel-oneAPI-Math-Kernel-Library/Incomplete-LU-Factorization-how-to-extract-L-and-U/m-p/830344#M5493 Alexander_K_Intel2 2012-01-18T03:49:02Z