*DECK R9LGMC FUNCTION R9LGMC (X) C***BEGIN PROLOGUE R9LGMC C***SUBSIDIARY C***PURPOSE Compute the log Gamma correction factor so that C LOG(GAMMA(X)) = LOG(SQRT(2*PI)) + (X-.5)*LOG(X) - X C + R9LGMC(X). C***LIBRARY SLATEC (FNLIB) C***CATEGORY C7E C***TYPE SINGLE PRECISION (R9LGMC-S, D9LGMC-D, C9LGMC-C) C***KEYWORDS COMPLETE GAMMA FUNCTION, CORRECTION TERM, FNLIB, C LOG GAMMA, LOGARITHM, SPECIAL FUNCTIONS C***AUTHOR Fullerton, W., (LANL) C***DESCRIPTION C C Compute the log gamma correction factor for X .GE. 10.0 so that C LOG (GAMMA(X)) = LOG(SQRT(2*PI)) + (X-.5)*LOG(X) - X + R9LGMC(X) C C Series for ALGM on the interval 0. to 1.00000D-02 C with weighted error 3.40E-16 C log weighted error 15.47 C significant figures required 14.39 C decimal places required 15.86 C C***REFERENCES (NONE) C***ROUTINES CALLED CSEVL, INITS, R1MACH, XERMSG C***REVISION HISTORY (YYMMDD) C 770801 DATE WRITTEN C 890531 Changed all specific intrinsics to generic. (WRB) C 890531 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 900720 Routine changed from user-callable to subsidiary. (WRB) C***END PROLOGUE R9LGMC DIMENSION ALGMCS(6) LOGICAL FIRST SAVE ALGMCS, NALGM, XBIG, XMAX, FIRST DATA ALGMCS( 1) / .1666389480 45186E0 / DATA ALGMCS( 2) / -.0000138494 817606E0 / DATA ALGMCS( 3) / .0000000098 108256E0 / DATA ALGMCS( 4) / -.0000000000 180912E0 / DATA ALGMCS( 5) / .0000000000 000622E0 / DATA ALGMCS( 6) / -.0000000000 000003E0 / DATA FIRST /.TRUE./ C***FIRST EXECUTABLE STATEMENT R9LGMC IF (FIRST) THEN NALGM = INITS (ALGMCS, 6, R1MACH(3)) XBIG = 1.0/SQRT(R1MACH(3)) XMAX = EXP (MIN(LOG(R1MACH(2)/12.0), -LOG(12.0*R1MACH(1))) ) ENDIF FIRST = .FALSE. C IF (X .LT. 10.0) CALL XERMSG ('SLATEC', 'R9LGMC', + 'X MUST BE GE 10', 1, 2) IF (X.GE.XMAX) GO TO 20 C R9LGMC = 1.0/(12.0*X) IF (X.LT.XBIG) R9LGMC = CSEVL (2.0*(10./X)**2-1., ALGMCS, NALGM)/X RETURN C 20 R9LGMC = 0.0 CALL XERMSG ('SLATEC', 'R9LGMC', 'X SO BIG R9LGMC UNDERFLOWS', 2, + 1) RETURN C END