qgaus.f90

FORTRANvisualfortran常用数值算法集及源码

SUBROUTINE qgaus(func,a,b,ss)
REAL a,b,ss,func
EXTERNAL func
INTEGER j
REAL dx,xm,xr,w(5),x(5)
SAVE w,x
DATA w/.2955242247,.2692667193,.2190863625,.1494513491,&
       .0666713443/
DATA x/.1488743389,.4333953941,.6794095682,.8650633666,&
       .9739065285/
xm=0.5*(b+a)
xr=0.5*(b-a)
ss=0
do j=1,5
  dx=xr*x(j)
  ss=ss+w(j)*(func(xm+dx)+func(xm-dx))
end do
ss=xr*ss
END SUBROUTINE qgaus