sla_lin_berr.f (3) - Linux Manuals
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.
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.
N is INTEGER The number of linear equations, i.e., the order of the matrix A. N >= 0.
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 is INTEGER The number of right hand sides, i.e., the number of columns of the matrices AYB, RES, and BERR. NRHS >= 0.
RES is REAL array, dimension (N,NRHS) The residual matrix, i.e., the matrix R in the relative backward error formula above.
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 is REAL array, dimension (NRHS) The componentwise relative backward error from the formula above.
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
- September 2012
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