CALCI0 Subroutine

private subroutine CALCI0(ARG, RESULT, JINT)

Explanation of machine-dependent constants

beta = Radix for the floating-point system maxexp = Smallest power of beta that overflows XSMALL = Positive argument such that 1.0 - X = 1.0 to machine precision for all ABS(X) .LE. XSMALL. XINF = Largest positive machine number; approximately betamaxexp XMAX = Largest argument acceptable to BESI0; Solution to equation:
W(X) * (1+1/(8X)+9/(128X2) = betamaxexp where W(X) = EXP(X)/SQRT(2PIX)

 Approximate values for some important machines are:

                      beta       maxexp       XSMALL

CRAY-1 (S.P.) 2 8191 3.55E-15 Cyber 180/855 under NOS (S.P.) 2 1070 3.55E-15 IEEE (IBM/XT, SUN, etc.) (S.P.) 2 128 2.98E-8 IEEE (IBM/XT, SUN, etc.) (D.P.) 2 1024 5.55D-17 IBM 3033 (D.P.) 16 63 6.95D-18 VAX (S.P.) 2 127 2.98E-8 VAX D-Format (D.P.) 2 127 6.95D-18 VAX G-Format (D.P.) 2 1023 5.55D-17

                           XINF          XMAX

CRAY-1 (S.P.) 5.45E+2465 5682.810 Cyber 180/855 under NOS (S.P.) 1.26E+322 745.893 IEEE (IBM/XT, SUN, etc.) (S.P.) 3.40E+38 91.900 IEEE (IBM/XT, SUN, etc.) (D.P.) 1.79D+308 713.986 IBM 3033 (D.P.) 7.23D+75 178.182 VAX (S.P.) 1.70D+38 91.203 VAX D-Format (D.P.) 1.70D+38 91.203 VAX G-Format (D.P.) 8.98D+307 713.293

Error returns

The program returns XINF for BESI0 for ABS(ARG) .GT. XMAX.

Intrinsic functions required are:

 ABS, SQRT, EXP

Authors: W. J. Cody and L. Stoltz Mathematics and Computer Science Division Argonne National Laboratory Argonne, IL 60439

Latest modification: June 7, 1988

Arguments