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DQL12.FOR
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1985-11-29
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2KB
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69 lines
C
C ..................................................................
C
C SUBROUTINE DQL12
C
C PURPOSE
C TO COMPUTE INTEGRAL(EXP(-X)*FCT(X), SUMMED OVER X
C FROM 0 TO INFINITY).
C
C USAGE
C CALL DQL12 (FCT,Y)
C PARAMETER FCT REQUIRES AN EXTERNAL STATEMENT
C
C DESCRIPTION OF PARAMETERS
C FCT - THE NAME OF AN EXTERNAL DOUBLE PRECISION FUNCTION
C SUBPROGRAM USED.
C Y - THE RESULTING DOUBLE PRECISION INTEGRAL VALUE.
C
C REMARKS
C NONE
C
C SUBROUTINES AND FUNCTION SUBPROGRAMS REQUIRED
C THE EXTERNAL DOUBLE PRECISION FUNCTION SUBPROGRAM FCT(X)
C MUST BE FURNISHED BY THE USER.
C
C METHOD
C EVALUATION IS DONE BY MEANS OF 12-POINT GAUSSIAN-LAGUERRE
C QUADRATURE FORMULA, WHICH INTEGRATES EXACTLY,
C WHENEVER FCT(X) IS A POLYNOMIAL UP TO DEGREE 23.
C FOR REFERENCE, SEE
C SHAO/CHEN/FRANK, TABLES OF ZEROS AND GAUSSIAN WEIGHTS OF
C CERTAIN ASSOCIATED LAGUERRE POLYNOMIALS AND THE RELATED
C GENERALIZED HERMITE POLYNOMIALS, IBM TECHNICAL REPORT
C TR00.1100 (MARCH 1964), PP.24-25.
C
C ..................................................................
C
SUBROUTINE DQL12(FCT,Y)
C
C
DOUBLE PRECISION X,Y,FCT
C
X=.37099121044466920D2
Y=.8148077467426242D-15*FCT(X)
X=.28487967250984000D2
Y=Y+.30616016350350208D-11*FCT(X)
X=.22151090379397006D2
Y=Y+.13423910305150041D-8*FCT(X)
X=.17116855187462256D2
Y=Y+.16684938765409103D-6*FCT(X)
X=.13006054993306348D2
Y=Y+.8365055856819799D-5*FCT(X)
X=.9621316842456867D1
Y=Y+.20323159266299939D-3*FCT(X)
X=.68445254531151773D1
Y=Y+.26639735418653159D-2*FCT(X)
X=.45992276394183485D1
Y=Y+.20102381154634097D-1*FCT(X)
X=.28337513377435072D1
Y=Y+.9044922221168093D-1*FCT(X)
X=.15126102697764188D1
Y=Y+.24408201131987756D0*FCT(X)
X=.61175748451513067D0
Y=Y+.37775927587313798D0*FCT(X)
X=.11572211735802068D0
Y=Y+.26473137105544319D0*FCT(X)
RETURN
END