https://community.intel.com/t5/Intel-oneAPI-Math-Kernel-Library/Constant-residual-in-GMRES/m-p/793617#M2456 This post should be moved to the MKL forum.<BR /><BR />If you are able to post a small example code that displays the problematic behavior that you described, that code would facilitate identifying the sources of the problems. <BR /><BR />The first suspect in such cases, where a complex library is used, is errors in the subroutine argument types/values and proper sequencing of calls.<BR /> Mon, 14 Nov 2011 12:56:48 GMT mecej4 2011-11-14T12:56:48Z https://community.intel.com/t5/Intel-oneAPI-Math-Kernel-Library/Constant-residual-in-GMRES/m-p/793616#M2455 Hi all<BR />I am trying to solve a sparse system of linear equations using GMRES (7600 x 7600). Ihave not done any preconditioning yet. The problem I am facing is that after a certain number of iterations, the residual between two consecutive steps does not change. Well, it does change but very very slowly. I am talking about 1d-12 or smaller per iteration.<BR /><BR />The system of equations solved nicely with PARDISO. As I need to solve a large system later on, I really need to get GMRES to work. Does anyone know any remedy to this problem? Another thing I should mention is that the iterative solver does not stop even when the maximum number of iterations specified has been exceeded. It just kept on iterating. Why is this so?<BR /><BR />One final thing, does the arrangement of the system of equations affect the convergence of the solver? I have tried arranging it both ways and both of them gave the same outcome.<BR /><BR />Thank you.<BR /><BR />Best wishes,<BR />EH Mon, 14 Nov 2011 07:58:44 GMT https://community.intel.com/t5/Intel-oneAPI-Math-Kernel-Library/Constant-residual-in-GMRES/m-p/793616#M2455 eh4 2011-11-14T07:58:44Z https://community.intel.com/t5/Intel-oneAPI-Math-Kernel-Library/Constant-residual-in-GMRES/m-p/793617#M2456 This post should be moved to the MKL forum.<BR /><BR />If you are able to post a small example code that displays the problematic behavior that you described, that code would facilitate identifying the sources of the problems. <BR /><BR />The first suspect in such cases, where a complex library is used, is errors in the subroutine argument types/values and proper sequencing of calls.<BR /> Mon, 14 Nov 2011 12:56:48 GMT https://community.intel.com/t5/Intel-oneAPI-Math-Kernel-Library/Constant-residual-in-GMRES/m-p/793617#M2456 mecej4 2011-11-14T12:56:48Z