umf_lusolve

solve a linear sparse system given the LU factors

Calling Sequence

[x] = umf_lusolve(LU_ptr, b [, st, A])

Arguments

:LU_ptr a pointer to umf lu factors (L,U,p,q,R) : :b a real or complex column vector or a matrix (multiple rhs) : :st (optional) a string “Ax=b” (default) or “Ax’=b” (to be written

“Ax’‘=b” in scilab langage: a quote in a string must be doubled !)

: :A (optional) the sparse square matrix corresponding to the LU

factors (LU_ptr must be got with LU_ptr = umf_lufact(A))

: :x a column vector or a matrix in case of multiple rhs ( x(:,i) is

solution of A x(:,i) = b(:,i) or A’x(:,i) = b(:,i) )

:

Description

This function must be used in conjonction with umf_lufact which computes the LU factors of a sparse matrix. The optional st argument lets us choose between the solving of Ax=b (general case) or of A’x=b (sometimes useful). If you give the 4th argument then iterative refinement will be also proceceed (as in umfpack) to give a better numerical solution.

Examples

see the example section of umf_lufact

See Also

• umfpack solve sparse linear system
• umf_lufact lu factorisation of a sparse matrix
• umf_luget retrieve lu factors at the scilab level
• umf_ludel utility function used with umf_lufact
• umf_luinfo get information on LU factors