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dlamchf77.f(3) LAPACK dlamchf77.f(3)dlamchf77.fNAME-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) DLAMC5SYNOPSISFunction/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 =, 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.-28625AuthorGenerated automatically by Doxygen for LAPACK from the source code.Version 3.4.2Tue Sep 25 2012 dlamchf77.f(3)

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