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See the recommended documentation of this function

Scilab help >> UMFPACK Interface (sparse) > umf_lusolve

# 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

• 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
 Report an issue << umf_luinfo UMFPACK Interface (sparse) umfpack >>