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dlamchf77-f(3)

dlamchf77.f –

Synopsis

Functions/Subroutines

DOUBLE PRECISION function dlamch (CMACH)
DLAMCHF77 deprecated
subroutine dlamc1 (BETA, T, RND, IEEE1)
DLAMC1
subroutine dlamc2 (BETA, T, RND, EPS, EMIN, RMIN, EMAX, RMAX)
DLAMC2
DOUBLE PRECISION function dlamc3 (A, B)
DLAMC3
subroutine dlamc4 (EMIN, START, BASE)
DLAMC4
subroutine dlamc5 (BETA, P, EMIN, IEEE, EMAX, RMAX)
DLAMC5

Function/Subroutine Documentation

subroutine dlamc1 (integerBETA, integerT, logicalRND, logicalIEEE1)

DLAMC1 Purpose:

 DLAMC1 determines the machine parameters given by BETA, T, RND, and
 IEEE1.

Parameters:

BETA

 The base of the machine.

T

 The number of ( BETA ) digits in the mantissa.

RND

 Specifies whether proper rounding ( RND = .TRUE. ) or
 chopping ( RND = .FALSE. ) occurs in addition. This may not
 be a reliable guide to the way in which the machine performs
 its arithmetic.

IEEE1

 Specifies whether rounding appears to be done in the IEEE
 'round to nearest' style.

 

Author:

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

Date:

April 2012

Further Details

 The routine is based on the routine ENVRON by Malcolm and
 incorporates suggestions by Gentleman and Marovich. See
 Malcolm M. A. (1972) Algorithms to reveal properties of
 floating-point arithmetic. Comms. of the ACM, 15, 949-951.
 Gentleman W. M. and Marovich S. B. (1974) More on algorithms
 that reveal properties of floating point arithmetic units.
 Comms. of the ACM, 17, 276-277.

 

Definition at line 206 of file dlamchf77.f.

subroutine dlamc2 (integerBETA, integerT, logicalRND, double precisionEPS, integerEMIN, double precisionRMIN, integerEMAX, double precisionRMAX)

DLAMC2 Purpose:

 DLAMC2 determines the machine parameters specified in its argument
 list.

 

Author:

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

Date:

April 2012

Parameters:

BETA

 The base of the machine.

T

 The number of ( BETA ) digits in the mantissa.

RND

 Specifies whether proper rounding ( RND = .TRUE. ) or
 chopping ( RND = .FALSE. ) occurs in addition. This may not
 be a reliable guide to the way in which the machine performs
 its arithmetic.

EPS

 The smallest positive number such that
 fl( 1.0 - EPS ) .LT. 1.0,
 where fl denotes the computed value.

EMIN

 The minimum exponent before (gradual) underflow occurs.

RMIN

 The smallest normalized number for the machine, given by
 BASE**( EMIN - 1 ), where BASE is the floating point value
 of BETA.

EMAX

 The maximum exponent before overflow occurs.

RMAX

 The largest positive number for the machine, given by
 BASE**EMAX * ( 1 - EPS ), where BASE is the floating point
 value of BETA.

Further Details

 The computation of EPS is based on a routine PARANOIA by
 W. Kahan of the University of California at Berkeley.

 

Definition at line 419 of file dlamchf77.f.

DOUBLE PRECISION function dlamc3 (double precisionA, double precisionB)

DLAMC3 Purpose:

 DLAMC3 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.

Parameters:

A
B

 The values A and B.

 

Definition at line 642 of file dlamchf77.f.

subroutine dlamc4 (integerEMIN, double precisionSTART, integerBASE)

DLAMC4 Purpose:

 DLAMC4 is a service routine for DLAMC2.

Parameters:

EMIN

 The minimum exponent before (gradual) underflow, computed by
 setting A = START and dividing by BASE until the previous A
 can not be recovered.

START

 The starting point for determining EMIN.

BASE

 The base of the machine.

 

Definition at line 689 of file dlamchf77.f.

subroutine dlamc5 (integerBETA, integerP, integerEMIN, logicalIEEE, integerEMAX, double precisionRMAX)

DLAMC5 Purpose:

 DLAMC5 attempts to compute RMAX, the largest machine floating-point
 number, without overflow. It assumes that EMAX + abs(EMIN) sum
 approximately to a power of 2. It will fail on machines where this
 assumption does not hold, for example, the Cyber 205 (EMIN = -28625,
 EMAX = 28718). It will also fail if the value supplied for EMIN is
 too large (i.e. too close to zero), probably with overflow.

Parameters:

BETA

 The base of floating-point arithmetic.

P

 The number of base BETA digits in the mantissa of a
 floating-point value.

EMIN

 The minimum exponent before (gradual) underflow.

IEEE

 A logical flag specifying whether or not the arithmetic
 system is thought to comply with the IEEE standard.

EMAX

 The largest exponent before overflow

RMAX

 The largest machine floating-point number.

 

Definition at line 796 of file dlamchf77.f.

DOUBLE PRECISION function dlamch (characterCMACH)

DLAMCHF77 deprecated Purpose:

 DLAMCHF77 determines double precision machine parameters.

 

Parameters:

CMACH

 Specifies the value to be returned by DLAMCH:
 = 'E' or 'e', DLAMCH := eps
 = 'S' or 's , DLAMCH := sfmin
 = 'B' or 'b', DLAMCH := base
 = 'P' or 'p', DLAMCH := eps*base
 = 'N' or 'n', DLAMCH := t
 = 'R' or 'r', DLAMCH := rnd
 = 'M' or 'm', DLAMCH := emin
 = 'U' or 'u', DLAMCH := rmin
 = 'L' or 'l', DLAMCH := emax
 = 'O' or 'o', DLAMCH := 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.

Date:

April 2012

Definition at line 64 of file dlamchf77.f.

Author

Generated automatically by Doxygen for LAPACK from the source code.