# octave can not solve x=A\B, but freemat can

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## octave can not solve x=A\B, but freemat can

 I am into a 1D-FE consolidation model and am quite surprise to see that the linear system based on sparse coefficient Matrix A and RHS-vector B cannot be solved by octave but without any problem in freemat. Apparently freemat investigates the structure of A and chooses the "right" solver for the specific matrix. Octave instead gives me warnings: "octave warning: inverse: matrix singular to machine precision, rcond = 0" However I have no idea how to find the "right" solver for this quite simple operation x=A\B.Is there a way to tell octave, the way it works on freemat,  to look for the most appropriate solver? Any hints highly appreciated!tom _______________________________________________ Help-octave mailing list [hidden email] https://lists.gnu.org/mailman/listinfo/help-octave A numerical poem: Now the fifth daughter on the twelfth night Told the first father that things weren’t right My complexion she said is much too white He said come here and step into the light, he says hmm you’re right Let me tell the second mother this has been done But the second mother was with the seventh son And they were both out on Highway 61 ("Highway 61" by Robert Zimmerman 1964)
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## Re: octave can not solve x=A\B, but freemat can

 Hi Tom,Can you provide Octave code to reproduce your problem?Nir _______________________________________________ Help-octave mailing list [hidden email] https://lists.gnu.org/mailman/listinfo/help-octave
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## Re: octave can not solve x=A\B, but freemat can

 In reply to this post by tomdylan On 1 Apr 2014, at 18:01, TDylan <[hidden email]> wrote: > I am into a 1D-FE consolidation model and am quite surprise to see that the linear system based on sparse coefficient Matrix A and RHS-vector B cannot be solved by octave but without any problem in freemat. > > Apparently freemat investigates the structure of A and chooses the "right" solver for the specific matrix. Octave instead gives me warnings: > > "octave warning: inverse: matrix singular to machine precision, rcond = 0" > > However I have no idea how to find the "right" solver for this quite simple operation x=A\B. > > Is there a way to tell octave, the way it works on freemat,  to look for the most appropriate solver? > > Any hints highly appreciated! > > tom Have you read the manual? http://www.gnu.org/software/octave/doc/interpreter/Techniques-Used-for-Linear-Algebra.html#Techniques-Used-for-Linear-AlgebraI cannot tell for sure without seeing your matrix, but I suspect it falls under case 4. c. _______________________________________________ Help-octave mailing list [hidden email] https://lists.gnu.org/mailman/listinfo/help-octave