求大神帮助，使用fortran的版本很旧，是自学的

hcj

[Fortran] 纯文本查看 复制代码

      PROGRAM MAIN
        EXTERNAL D
        DOUBLE PRECISION D,e,D1
        DO e=0.1,1.0,0.01
        D1=D(e)
      WRITE(*,*)D1
        END DO

        END

        FUNCTION D(e)
        EXTERNAL F5
        DOUBLE PRECISION D,F5,G5,e
        CALL FLAGS2(F5,G5,e)
C        WRITE(*,*)G5
        D=G5

        END

        FUNCTION F5(b,e)
        EXTERNAL IS,IC
        DOUBLE PRECISION F5,IS,IC,b,e
        F5=(1/3.1415926)*(COS(b*(e-IC(b))))*EXP(-1*b*IS(b))
        RETURN

        END

        FUNCTION IS(b)
        EXTERNAL F4
        DOUBLE PRECISION IS,F4,G4,b
        CALL FLAGS2(F4,G4,b)
C        WRITE(*,*)G4
        IS=G4

        END

        FUNCTION F4(V1,b)
        EXTERNAL N
        DOUBLE PRECISION F4,N,V1,b
        F4=(SIN(b*V1))*N(V1)
        RETURN

        END

        FUNCTION IC(b)
        EXTERNAL F3
        DOUBLE PRECISION IC,F3,G3,b
        CALL FLAGS2(F3,G3,b)
C        WRITE(*,*)G3
        IC=G3
        
        END

        FUNCTION F3(V1,b)
        EXTERNAL N
        DOUBLE PRECISION F3,b,V1,N
        F3=(COS(b*V1))*N(V1)
        RETURN

        END

        FUNCTION N(V1)
        EXTERNAL F1,F2
        DOUBLE PRECISION N,V1,F1,F2,V
        N=F1(V)-F2(V1)
        RETURN

        END

        FUNCTION F2(V1)
        EXTERNAL F
        DOUBLE PRECISION F2,V1,F,A,B,G1
        A=0.0
        B=V1
        EPS=0.005
        CALL FLAGS1(A,B,F,EPS,G1)
C        WRITE(*,*)G1
        F2=G1

        END

        FUNCTION F1(V)
        EXTERNAL F
        DOUBLE PRECISION F1,F,G,V
        CALL FLAGS(F,G)
C        WRITE(*,*)G
        F1=G

        END
        
        FUNCTION F(V)
        DOUBLE PRECISION F,V
        F=(3/(2*3.1415926*V))*LOG((COSH(SQRT(1/(2*V)))**2-
     *        COS(SQRT(1/(2*V)))**2)/(2*V))
        RETURN

        END

      SUBROUTINE FLAGS(F,G)
        DIMENSION T(5),C(5)
        DOUBLE PRECISION F,G,T,C,X
        DATA C/0.6790941054,1.638487956,2.769426772,
     *       4.31594400,7.104896230/
        DATA T/0.26355990,1.41340290,3.59642600,
     *       7.08580990,12.64080000/

        
        G=0.0D0
        DO 10 I=1,5
          X=T(I)
          G=G+F(X)*C(I)
10    CONTINUE

        END

        SUBROUTINE FLAGS1(A,B,F,EPS,G)            
        DIMENSION T(5),C(5)
        DOUBLE PRECISION A,B,F,G,T,C,S,P,H,AA,BB,W,X,Q
        DATA T/-0.061798459,-0.5384693101,0.0,
     *       0.5384693101,0.9061798459/
        DATA C/0.2369268851,0.4786286705,0.5688888889,
     *       0.4786286705,0.2369268851/
        M=1
        S=(B-A)*0.001
        P=0.0
10    H=(B-A)/M
        G=0.0
        DO 30 I=1,M
         AA=A+(I-1)*H
         BB=A+I*H
         W=0.0
         DO 20 J=1,5
          X=((BB-AA)*T(J)+(BB+AA))/2.0
          W=W+F(X)*C(J)
20         CONTINUE
       G=G+W 
30    CONTINUE
      G=G*H/2.0
        Q=ABS(G-P)/(1.0+ABS(G))[attach]2078[/attach][attach]2078[/attach][attach]2078[/attach]
        IF ((Q.GE.EPS).AND.(ABS(H).GT.ABS(S)))THEN
          P=G
          M=M+1
          GOTO 10
        END IF
        RETURN
        
        END

      SUBROUTINE FLAGS2(F,G,b)
        DIMENSION T(5),C(5)
        DOUBLE PRECISION F,G,T,C,X,b
        DATA C/0.6790941054,1.638487956,2.769426772,
     *       4.31594400,7.104896230/
        DATA T/0.26355990,1.41340290,3.59642600,
     *       7.08580990,12.64080000/

        
        G=0.0D0
        DO 10 I=1,5
          X=T(I)
          G=G+F(X,b)*C(I)
10    CONTINUE

        END

liudy02

新学FORTRAN，我觉得不要学老的那一套，把彭国伦的书和查普曼的书好好学学才是正经事

li913

你的问题是啥?

hcj

li913 发表于 2018-11-13 16:07
你的问题是啥?

解决这个积分

li913

没法直接做无穷积分。你得想其他法儿，比如积分变换、傅氏变换等。

liudy02

li913 发表于 2018-11-16 20:48
没法直接做无穷积分。你得想其他法儿，比如积分变换、傅氏变换等。

应该可以用有限区间积分+收敛性判定吧，不过这事没啥意思
应该有现成的软件或者函数库干这个事情吧