29 lines
621 B
Fortran
29 lines
621 B
Fortran
SUBROUTINE midexp(funk,aa,bb,s,n)
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INTEGER n
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REAL aa,bb,s,funk
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EXTERNAL funk
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INTEGER it,j
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REAL ddel,del,sum,tnm,x,func,a,b
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func(x)=funk(-log(x))/x
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b=exp(-aa)
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a=0.
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if (n.eq.1) then
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s=(b-a)*func(0.5*(a+b))
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else
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it=3**(n-2)
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tnm=it
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del=(b-a)/(3.*tnm)
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ddel=del+del
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x=a+0.5*del
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sum=0.
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do 11 j=1,it
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sum=sum+func(x)
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x=x+ddel
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sum=sum+func(x)
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x=x+del
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11 continue
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s=(s+(b-a)*sum/tnm)/3.
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endif
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return
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END
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