d3r8.f90

Visual Fortran常用数值算法集

PROGRAM D3R8
!Driver for routine GAULEG
PARAMETER (NPOINT=10,X1=0.0,X2=1.0,X3=10.0)
DIMENSION X(NPOINT),W(NPOINT)
CALL GAULEG(X1,X2,X,W,NPOINT)
WRITE(*,'(/1X,T3,A,T10,A,T22,A/)') '#','X(I)','W(I)'
DO I=1,NPOINT
    WRITE(*,'(1X,I2,2F12.6)') I,X(I),W(I)
END DO
!Demonstrate the use of GAUEG for an integral
CALL GAULEG(X1,X3,X,W,NPOINT)
XX=0.0
DO I=1,NPOINT
    XX=XX+W(I)*FUNC(X(I))
END DO
WRITE(*,'(/1X,A,F12.6)') 'Integral from GAULEG:',XX
WRITE(*,'(1X,A,F12.6)')&
               'Actual value:',1.0-(1.0+X3)*EXP(-X3)
END PROGRAM
FUNCTION FUNC(X)
  FUNC=X*EXP(-X)
END FUNCTION FUNC