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*DECK I1MACH

      INTEGER FUNCTION i1mach (I)

C***BEGIN PROLOGUE  I1MACH

C***PURPOSE  Return integer machine dependent constants.

C***LIBRARY   SLATEC

C***CATEGORY  R1

C***TYPE      INTEGER (I1MACH-I)

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   I1MACH 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        K = I1MACH(I)

C

C   where I=1,...,16.  The (output) value of K above is determined by

C   the (input) value of I.  The results for various values of I are

C   discussed below.

C

C   I/O unit numbers:

C     I1MACH( 1) = the standard input unit.

C     I1MACH( 2) = the standard output unit.

C     I1MACH( 3) = the standard punch unit.

C     I1MACH( 4) = the standard error message unit.

C

C   Words:

C     I1MACH( 5) = the number of bits per integer storage unit.

C     I1MACH( 6) = the number of characters per integer storage unit.

C

C   Integers:

C     assume integers are represented in the S-digit, base-A form

C

C                sign ( X(S-1)*A**(S-1) + ... + X(1)*A + X(0) )

C

C                where 0 .LE. X(I) .LT. A for I=0,...,S-1.

C     I1MACH( 7) = A, the base.

C     I1MACH( 8) = S, the number of base-A digits.

C     I1MACH( 9) = A**S - 1, the largest magnitude.

C

C   Floating-Point Numbers:

C     Assume floating-point numbers are represented in the T-digit,

C     base-B form

C                sign (B**E)*( (X(1)/B) + ... + (X(T)/B**T) )

C

C                where 0 .LE. X(I) .LT. B for I=1,...,T,

C                0 .LT. X(1), and EMIN .LE. E .LE. EMAX.

C     I1MACH(10) = B, the base.

C

C   Single-Precision:

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   Double-Precision:

C     I1MACH(14) = T, the number of base-B digits.

C     I1MACH(15) = EMIN, the smallest exponent E.

C     I1MACH(16) = 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 I1MACH(1) - I1MACH(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  (NONE)

C***REVISION HISTORY  (YYMMDD)

C   750101  DATE WRITTEN

C   891012  Added VAX G-floating constants.  (WRB)

C   891012  REVISION DATE from Version 3.2

C   891214  Prologue converted to Version 4.0 format.  (BAB)

C   900618  Added DEC RISC constants.  (WRB)

C   900723  Added IBM RS 6000 constants.  (WRB)

C   901009  Correct I1MACH(7) for IBM Mainframes. Should be 2 not 16.

C           (RWC)

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   930618  Corrected I1MACH(5) for Convex -p8 and -pd8 compiler

C           options.  (DWL, RWC and WRB).

C   100623  Use Fortran 95 intrinsic functions (Lionel GUEZ)

C***END PROLOGUE  I1MACH

C

      INTEGER imach(16),output

      SAVE imach

      equivalence(imach(4),output)

C***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

C

      i1mach = imach(i)

      RETURN

C

   10 CONTINUE

      WRITE (unit = output, fmt = 9000)

 9000 FORMAT ('1ERROR    1 IN I1MACH - I OUT OF BOUNDS')

C

C     CALL FDUMP

C

      stop

      END