slamch.f File Reference

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Functions/Subroutines
real function	slamch (cmach)
	SLAMCH
real function	slamc3 (a, b)
	SLAMC3

Function/Subroutine Documentation

slamc3()

real function slamc3	(	real	a,
		real	b )

SLAMC3

Purpose:

!> SLAMC3  is intended to force  A  and  B  to be stored prior to doing
!> the addition of  A  and  B ,  for use in situations where optimizers
!> might hold one of these in a register.
!> 

Author

LAPACK is a software package provided by Univ. of Tennessee, Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..

Parameters

[in]	A	!>
[in]	B	!> The values A and B. !>

Definition at line 168 of file slamch.f.

*
*  -- LAPACK auxiliary routine --
*     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
*
*     .. Scalar Arguments ..
      REAL               A, B
*     ..
* =====================================================================
*
*     .. Executable Statements ..
*
      slamc3 = a + b
*
      RETURN
*
*     End of SLAMC3
*

slamch()

real function slamch

(

character

cmach

)

SLAMCH

Purpose:

!>
!> SLAMCH determines single precision machine parameters.
!> 

Parameters

[in]

CMACH

!> CMACH is CHARACTER*1 !> Specifies the value to be returned by SLAMCH: !> = 'E' or 'e', SLAMCH := eps !> = 'S' or 's , SLAMCH := sfmin !> = 'B' or 'b', SLAMCH := base !> = 'P' or 'p', SLAMCH := eps*base !> = 'N' or 'n', SLAMCH := t !> = 'R' or 'r', SLAMCH := rnd !> = 'M' or 'm', SLAMCH := emin !> = 'U' or 'u', SLAMCH := rmin !> = 'L' or 'l', SLAMCH := emax !> = 'O' or 'o', SLAMCH := rmax !> where !> eps = relative machine precision !> sfmin = safe minimum, such that 1/sfmin does not overflow !> base = base of the machine !> prec = eps*base !> t = number of (base) digits in the mantissa !> rnd = 1.0 when rounding occurs in addition, 0.0 otherwise !> emin = minimum exponent before (gradual) underflow !> rmin = underflow threshold - base**(emin-1) !> emax = largest exponent before overflow !> rmax = overflow threshold - (base**emax)*(1-eps) !>

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line 67 of file slamch.f.

*
*  -- LAPACK auxiliary routine --
*  -- LAPACK is a software package provided by Univ. of Tennessee,    --
*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
*
*     .. Scalar Arguments ..
      CHARACTER          CMACH
*     ..
*
* =====================================================================
*
*     .. Parameters ..
      REAL               ONE, ZERO
      parameter( one = 1.0e+0, zero = 0.0e+0 )
*     ..
*     .. Local Scalars ..
      REAL               RND, EPS, SFMIN, SMALL, RMACH
*     ..
*     .. External Functions ..
      LOGICAL            LSAME
      EXTERNAL           lsame
*     ..
*     .. Intrinsic Functions ..
      INTRINSIC          digits, epsilon, huge, maxexponent,
     $                   minexponent, radix, tiny
*     ..
*     .. Executable Statements ..
*
*
*     Assume rounding, not chopping. Always.
*
      rnd = one
*
      IF( one.EQ.rnd ) THEN
         eps = epsilon(zero) * 0.5
      ELSE
         eps = epsilon(zero)
      END IF
*
      IF( lsame( cmach, 'E' ) ) THEN
         rmach = eps
      ELSE IF( lsame( cmach, 'S' ) ) THEN
         sfmin = tiny(zero)
         small = one / huge(zero)
         IF( small.GE.sfmin ) THEN
*
*           Use SMALL plus a bit, to avoid the possibility of rounding
*           causing overflow when computing  1/sfmin.
*
            sfmin = small*( one+eps )
         END IF
         rmach = sfmin
      ELSE IF( lsame( cmach, 'B' ) ) THEN
         rmach = radix(zero)
      ELSE IF( lsame( cmach, 'P' ) ) THEN
         rmach = eps * radix(zero)
      ELSE IF( lsame( cmach, 'N' ) ) THEN
         rmach = digits(zero)
      ELSE IF( lsame( cmach, 'R' ) ) THEN
         rmach = rnd
      ELSE IF( lsame( cmach, 'M' ) ) THEN
         rmach = minexponent(zero)
      ELSE IF( lsame( cmach, 'U' ) ) THEN
         rmach = tiny(zero)
      ELSE IF( lsame( cmach, 'L' ) ) THEN
         rmach = maxexponent(zero)
      ELSE IF( lsame( cmach, 'O' ) ) THEN
         rmach = huge(zero)
      ELSE
         rmach = zero
      END IF
*
      slamch = rmach
      RETURN
*
*     End of SLAMCH
*