Note: this is a BLAS routine and is not in libslatec.a
*DECK R1MACH
REAL FUNCTION R1MACH (I)
C***BEGIN PROLOGUE R1MACH
C***PURPOSE Return floating point machine dependent constants.
C***LIBRARY SLATEC
C***CATEGORY R1
C***TYPE SINGLE PRECISION (R1MACH-S, D1MACH-D)
C***KEYWORDS MACHINE CONSTANTS
C***AUTHOR Fox, P. A., (Bell Labs)
C Hall, A. D., (Bell Labs)
C Schryer, N. L., (Bell Labs)
C***DESCRIPTION
C
C R1MACH can be used to obtain machine-dependent parameters for the
C local machine environment. It is a function subprogram with one
C (input) argument, and can be referenced as follows:
C
C A = R1MACH(I)
C
C where I=1,...,5. The (output) value of A above is determined by
C the (input) value of I. The results for various values of I are
C discussed below.
C
C R1MACH(1) = B**(EMIN-1), the smallest positive magnitude.
C R1MACH(2) = B**EMAX*(1 - B**(-T)), the largest magnitude.
C R1MACH(3) = B**(-T), the smallest relative spacing.
C R1MACH(4) = B**(1-T), the largest relative spacing.
C R1MACH(5) = LOG10(B)
C
C Assume single precision numbers are represented in the T-digit,
C base-B form
C
C sign (B**E)*( (X(1)/B) + ... + (X(T)/B**T) )
C
C where 0 .LE. X(I) .LT. B for I=1,...,T, 0 .LT. X(1), and
C EMIN .LE. E .LE. EMAX.
C
C The values of B, T, EMIN and EMAX are provided in I1MACH as
C follows:
C I1MACH(10) = B, the base.
C I1MACH(11) = T, the number of base-B digits.
C I1MACH(12) = EMIN, the smallest exponent E.
C I1MACH(13) = EMAX, the largest exponent E.
C
C To alter this function for a particular environment, the desired
C set of DATA statements should be activated by removing the C from
C column 1. Also, the values of R1MACH(1) - R1MACH(4) should be
C checked for consistency with the local operating system.
C
C***REFERENCES P. A. Fox, A. D. Hall and N. L. Schryer, Framework for
C a portable library, ACM Transactions on Mathematical
C Software 4, 2 (June 1978), pp. 177-188.
C***ROUTINES CALLED XERMSG
C***REVISION HISTORY (YYMMDD)
C 790101 DATE WRITTEN
C 890213 REVISION DATE from Version 3.2
C 891214 Prologue converted to Version 4.0 format. (BAB)
C 900315 CALLs to XERROR changed to CALLs to XERMSG. (THJ)
C 900618 Added DEC RISC constants. (WRB)
C 900723 Added IBM RS 6000 constants. (WRB)
C 910710 Added HP 730 constants. (SMR)
C 911114 Added Convex IEEE constants. (WRB)
C 920121 Added SUN -r8 compiler option constants. (WRB)
C 920229 Added Touchstone Delta i860 constants. (WRB)
C 920501 Reformatted the REFERENCES section. (WRB)
C 920625 Added CONVEX -p8 and -pd8 compiler option constants.
C (BKS, WRB)
C 930201 Added DEC Alpha and SGI constants. (RWC and WRB)
C***END PROLOGUE R1MACH