bessy1.f90

FORTRANvisualfortran常用数值算法集及源码

FUNCTION bessy1(x)
REAL bessy1,x
!USES bessj1
REAL xx,z,bessj1
DOUBLE PRECISION p1,p2,p3,p4,p5,q1,q2,q3,q4,q5,&
       r1,r2,r3,r4,r5,r6,s1,s2,s3,s4,s5,s6,s7,y
SAVE p1,p2,p3,p4,p5,q1,q2,q3,q4,q5,r1,r2,r3,r4,r5,r6,&
     s1,s2,s3,s4,s5,s6,s7
DATA p1,p2,p3,p4,p5/1.d0,.183105d-2,-.3516396496d-4,&
     .2457520174d-5,-.240337019d-6/, q1,q2,q3,q4,q5/&
	 .04687499995d0,-.2002690873d-3,.8449199096d-5,&
	 -.88228987d-6,.105787412d-6/
DATA r1,r2,r3,r4,r5,r6/-.4900604943d13,.1275274390d13,&
     -.5153438139d11,.7349264551d9,-.4237922726d7,&
	 .8511937935d4/,s1,s2,s3,s4,s5,s6,s7/.2499580570d14,&
	 .4244419664d12,.3733650367d10,.2245904002d8,&
	 .1020426050d6,.3549632885d3,1.d0/
if(x<8.)then
  y=x**2
  bessy1=x*(r1+y*(r2+y*(r3+y*(r4+y*(r5+y*r6)))))/&
         (s1+y*(s2+y*(s3+y*(s4+y*(s5+y*(s6+y*s7))))))&
		 +.636619772*(bessj1(x)*log(x)-1./x)
else
  z=8./x
  y=z**2
  xx=x-2.356194491
  bessy1=sqrt(.636619772/x)*(sin(xx)*(p1+y*(p2+y*&
         (p3+y*(p4+y*p5))))+z*cos(xx)*(q1+y*(q2+y*&
		 (q3+y*(q4+y*q5)))))
endif
END FUNCTION bessy1