source: trunk/fsource/texturesubs/dgammln.for @ 305

Last change on this file since 305 was 305, checked in by vondreele, 12 years ago

remove pypowder & powsubs - no longer needed
add texturesubs & pytexture

File size: 1.0 KB
Line 
1      FUNCTION DGAMMLN(XX)
2
3!PURPOSE: ln(gamma(xx)), taken from Numerical Recipes, p156-157
4
5      INCLUDE       '../INCLDS/COPYRIGT.FOR' 
6
7!PSEUDOCODE:
8
9!CALLING ARGUMENTS:
10
11      REAL*8        DGAMMLN              !ln(gamma(xx)) with xx>0
12      REAL*4        XX                  !argument must be >0
13
14!INCLUDE STATEMENTS:
15
16!LOCAL VARIABLES:
17
18      REAL*8        COF(6),STP,HALF,ONE,FPF,X,TMP,SER
19
20!SUBROUTINES CALLED:
21
22!FUNCTION DEFINITIONS:
23
24!DATA STATEMENTS:
25
26      DATA      COF,STP/76.18009172947146D0,-86.50532032941677D0,
27     1  24.01409824083091D0,-1.231739572450155D0,0.1208650973866D-2,
28     1  -0.5395239384953D-5,2.5066282746310005D0/
29      DATA      HALF,ONE,FPF/0.5D0,1.000000000190015D0,5.5D0/
30
31!CODE:
32                                           
33      X = XX-ONE
34      TMP = X+FPF
35      TMP = (X+HALF)*DLOG(TMP)-TMP
36      SER = ONE
37      DO J=1,6
38        X = X+ONE
39        SER = SER+COF(J)/X
40      END DO
41      DGAMMLN = TMP+DLOG(STP*SER)
42      RETURN
43      END
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