slazq4 (l) - Linux Manuals

slazq4: an approximation TAU to the smallest eigenvalue using values of d from the previous transform

NAME

SLAZQ4 - an approximation TAU to the smallest eigenvalue using values of d from the previous transform

SYNOPSIS

SUBROUTINE SLAZQ4(
I0, N0, Z, PP, N0IN, DMIN, DMIN1, DMIN2, DN, DN1, DN2, TAU, TTYPE, G )

    
INTEGER I0, N0, N0IN, PP, TTYPE

    
REAL DMIN, DMIN1, DMIN2, DN, DN1, DN2, G, TAU

    
REAL Z( * )

PURPOSE

SLAZQ4 computes an approximation TAU to the smallest eigenvalue using values of d from the previous transform.

I0 (input) INTEGER

First index.

N0 (input) INTEGER

Last index.

Z (input) REAL array, dimension ( 4*N )

Z holds the qd array.

PP (input) INTEGER

PP=0 for ping, PP=1 for pong.

N0IN (input) INTEGER

The value of N0 at start of EIGTEST.

DMIN (input) REAL

Minimum value of d.

DMIN1 (input) REAL

Minimum value of d, excluding D( N0 ).

DMIN2 (input) REAL

Minimum value of d, excluding D( N0 ) and D( N0-1 ).

DN (input) REAL

d(N)

DN1 (input) REAL

d(N-1)

DN2 (input) REAL

d(N-2)

TAU (output) REAL

This is the shift.

TTYPE (output) INTEGER

Shift type.

G (input/output) REAL

G is passed as an argument in order to save its value between
calls to SLAZQ4

FURTHER DETAILS

This is a thread safe version of SLASQ4, which passes G through the argument list in place of declaring G in a SAVE statment.

Pages related to slazq4

  • slazq3 (l) - for deflation, computes a shift (TAU) and calls dqds
  • sla_gbamv (l) - performs one of the matrix-vector operations y := alpha*abs(A)*abs(x) + beta*abs(y),
  • sla_gbrcond (l) - SLA_GERCOND Estimate the Skeel condition number of op(A) * op2(C) where op2 is determined by CMODE as follows CMODE = 1 op2(C) = C CMODE = 0 op2(C) = I CMODE = -1 op2(C) = inv(C) The Skeel condition number cond(A) = norminf( |inv(A)||A| ) is computed by computing scaling factors R such that diag(R)*A*op2(C) is row equilibrated and computing the standard infinity-norm condition number
  • sla_gbrfsx_extended (l) - computes ..
  • sla_geamv (l) - performs one of the matrix-vector operations y := alpha*abs(A)*abs(x) + beta*abs(y),
  • sla_gercond (l) - SLA_GERCOND estimate the Skeel condition number of op(A) * op2(C) where op2 is determined by CMODE as follows CMODE = 1 op2(C) = C CMODE = 0 op2(C) = I CMODE = -1 op2(C) = inv(C) The Skeel condition number cond(A) = norminf( |inv(A)||A| ) is computed by computing scaling factors R such that diag(R)*A*op2(C) is row equilibrated and computing the standard infinity-norm condition number
  • sla_gerfsx_extended (l) - computes ..
  • sla_lin_berr (l) - SLA_LIN_BERR compute component-wise 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 component-wise absolute value of the matrix or vector Z