00001 REAL FUNCTION genexp(av) 00002 00003 C********************************************************************** 00004 C 00005 C REAL FUNCTION GENEXP( AV ) 00006 C 00007 C GENerate EXPonential random deviate 00008 C 00009 C 00010 C Function 00011 C 00012 C 00013 C Generates a single random deviate from an exponential 00014 C distribution with mean AV. 00015 C 00016 C 00017 C Arguments 00018 C 00019 C 00020 C AV --> The mean of the exponential distribution from which 00021 C a random deviate is to be generated. 00022 C REAL AV 00023 C JJV (AV >= 0) 00024 C 00025 C GENEXP <-- The random deviate. 00026 C REAL GENEXP 00027 C 00028 C 00029 C Method 00030 C 00031 C 00032 C Renames SEXPO from TOMS as slightly modified by BWB to use RANF 00033 C instead of SUNIF. 00034 C 00035 C For details see: 00036 C 00037 C Ahrens, J.H. and Dieter, U. 00038 C Computer Methods for Sampling From the 00039 C Exponential and Normal Distributions. 00040 C Comm. ACM, 15,10 (Oct. 1972), 873 - 882. 00041 C 00042 C********************************************************************** 00043 C .. Scalar Arguments .. 00044 REAL av 00045 C .. 00046 C .. External Functions .. 00047 REAL sexpo 00048 EXTERNAL sexpo 00049 C .. 00050 C .. Executable Statements .. 00051 C JJV added check to ensure AV >= 0.0 00052 IF (av.GE.0.0) GO TO 10 00053 WRITE (*,*) 'AV < 0.0 in GENEXP - ABORT' 00054 WRITE (*,*) 'Value of AV: ',av 00055 CALL XSTOPX ('AV < 0.0 in GENEXP - ABORT') 00056 00057 10 genexp = sexpo()*av 00058 RETURN 00059 00060 END
1.7.1
