!DECK I1MACH INTEGER FUNCTION I1MACH (I) IMPLICIT NONE !***BEGIN PROLOGUE I1MACH !***PURPOSE Return integer machine dependent constants. !***LIBRARY SLATEC !***CATEGORY R1 !***TYPE INTEGER (I1MACH-I) !***KEYWORDS MACHINE CONSTANTS !***AUTHOR Fox, P. A., (Bell Labs) ! Hall, A. D., (Bell Labs) ! Schryer, N. L., (Bell Labs) !***DESCRIPTION ! ! I1MACH can be used to obtain machine-dependent parameters for the ! local machine environment. It is a function subprogram with one ! (input) argument and can be referenced as follows: ! ! K = I1MACH(I) ! ! where I=1,...,16. The (output) value of K above is determined by ! the (input) value of I. The results for various values of I are ! discussed below. ! ! I/O unit numbers: ! I1MACH( 1) = the standard input unit. ! I1MACH( 2) = the standard output unit. ! I1MACH( 3) = the standard punch unit. ! I1MACH( 4) = the standard error message unit. ! ! Words: ! I1MACH( 5) = the number of bits per integer storage unit. ! I1MACH( 6) = the number of characters per integer storage unit. ! ! Integers: ! assume integers are represented in the S-digit, base-A form ! ! sign ( X(S-1)*A**(S-1) + ... + X(1)*A + X(0) ) ! ! where 0 .LE. X(I) .LT. A for I=0,...,S-1. ! I1MACH( 7) = A, the base. ! I1MACH( 8) = S, the number of base-A digits. ! I1MACH( 9) = A**S - 1, the largest magnitude. ! ! Floating-Point Numbers: ! Assume floating-point numbers are represented in the T-digit, ! base-B form ! sign (B**E)*( (X(1)/B) + ... + (X(T)/B**T) ) ! ! where 0 .LE. X(I) .LT. B for I=1,...,T, ! 0 .LT. X(1), and EMIN .LE. E .LE. EMAX. ! I1MACH(10) = B, the base. ! ! Single-Precision: ! I1MACH(11) = T, the number of base-B digits. ! I1MACH(12) = EMIN, the smallest exponent E. ! I1MACH(13) = EMAX, the largest exponent E. ! ! Double-Precision: ! I1MACH(14) = T, the number of base-B digits. ! I1MACH(15) = EMIN, the smallest exponent E. ! I1MACH(16) = EMAX, the largest exponent E. ! ! To alter this function for a particular environment, the desired ! set of DATA statements should be activated by removing the C from ! column 1. Also, the values of I1MACH(1) - I1MACH(4) should be ! checked for consistency with the local operating system. ! !***REFERENCES P. A. Fox, A. D. Hall and N. L. Schryer, Framework for ! a portable library, ACM Transactions on Mathematical ! Software 4, 2 (June 1978), pp. 177-188. !***ROUTINES CALLED (NONE) !***REVISION HISTORY (YYMMDD) ! 750101 DATE WRITTEN ! 891012 Added VAX G-floating constants. (WRB) ! 891012 REVISION DATE from Version 3.2 ! 891214 Prologue converted to Version 4.0 format. (BAB) ! 900618 Added DEC RISC constants. (WRB) ! 900723 Added IBM RS 6000 constants. (WRB) ! 901009 Correct I1MACH(7) for IBM Mainframes. Should be 2 not 16. ! (RWC) ! 910710 Added HP 730 constants. (SMR) ! 911114 Added Convex IEEE constants. (WRB) ! 920121 Added SUN -r8 compiler option constants. (WRB) ! 920229 Added Touchstone Delta i860 constants. (WRB) ! 920501 Reformatted the REFERENCES section. (WRB) ! 920625 Added Convex -p8 and -pd8 compiler option constants. ! (BKS, WRB) ! 930201 Added DEC Alpha and SGI constants. (RWC and WRB) ! 930618 Corrected I1MACH(5) for Convex -p8 and -pd8 compiler ! options. (DWL, RWC and WRB). ! 100623 Use Fortran 95 intrinsic functions (Lionel GUEZ) !***END PROLOGUE I1MACH ! INTEGER :: IMACH(16),OUTPUT SAVE IMACH EQUIVALENCE (IMACH(4),OUTPUT) INTEGER :: I !***FIRST EXECUTABLE STATEMENT I1MACH IMACH( 1) = 5 IMACH( 2) = 6 IMACH( 3) = 6 IMACH( 4) = 6 IMACH( 5) = bit_size(0) IMACH( 6) = IMACH( 5) / 8 IMACH( 7) = radix(0) IMACH( 8) = digits(0) IMACH( 9) = huge(0) IMACH(10) = radix(0.) IMACH(11) = digits(0.) IMACH(12) = minexponent(0.) IMACH(13) = maxexponent(0.) IMACH(14) = digits(0d0) IMACH(15) = minexponent(0d0) IMACH(16) = maxexponent(0d0) IF (I .LT. 1 .OR. I .GT. 16) GO TO 10 ! I1MACH = IMACH(I) RETURN ! 10 CONTINUE WRITE (UNIT = OUTPUT, FMT = 9000) 9000 FORMAT ('1ERROR 1 IN I1MACH - I OUT OF BOUNDS') ! ! CALL FDUMP ! STOP END FUNCTION I1MACH