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