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sla_lin_berr.f(3) LAPACK sla_lin_berr.f(3)

NAME

sla_lin_berr.f -

SYNOPSIS

Functions/Subroutines


subroutine sla_lin_berr (N, NZ, NRHS, RES, AYB, BERR)
 
SLA_LIN_BERR computes a component-wise relative backward error.

Function/Subroutine Documentation

subroutine sla_lin_berr (integerN, integerNZ, integerNRHS, real, dimension( n, nrhs )RES, real, dimension( n, nrhs )AYB, real, dimension( nrhs )BERR)

SLA_LIN_BERR computes a component-wise relative backward error.
Purpose: 
    SLA_LIN_BERR computes componentwise relative backward error from
    the formula
        max(i) ( abs(R(i)) / ( abs(op(A_s))*abs(Y) + abs(B_s) )(i) )
    where abs(Z) is the componentwise absolute value of the matrix
    or vector Z.
Parameters:
N 
          N is INTEGER
     The number of linear equations, i.e., the order of the
     matrix A.  N >= 0.
NZ 
          NZ is INTEGER
     We add (NZ+1)*SLAMCH( 'Safe minimum' ) to R(i) in the numerator to
     guard against spuriously zero residuals. Default value is N.
NRHS 
          NRHS is INTEGER
     The number of right hand sides, i.e., the number of columns
     of the matrices AYB, RES, and BERR.  NRHS >= 0.
RES 
          RES is REAL array, dimension (N,NRHS)
     The residual matrix, i.e., the matrix R in the relative backward
     error formula above.
AYB 
          AYB is REAL array, dimension (N, NRHS)
     The denominator in the relative backward error formula above, i.e.,
     the matrix abs(op(A_s))*abs(Y) + abs(B_s). The matrices A, Y, and B
     are from iterative refinement (see sla_gerfsx_extended.f).
BERR 
          BERR is REAL array, dimension (NRHS)
     The componentwise relative backward error from the formula above.
Author:
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
September 2012
Definition at line 102 of file sla_lin_berr.f.

Author

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