besi0.f
1.61 KB
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function besi0 (x)
c april 1977 version. w. fullerton, c3, los alamos scientific lab.
dimension bi0cs(12)
external besi0e, csevl, inits, r1mach
c
c series for bi0 on the interval 0. to 9.00000d+00
c with weighted error 2.46e-18
c log weighted error 17.61
c significant figures required 17.90
c decimal places required 18.15
c
data bi0 cs( 1) / -.0766054725 2839144951e0 /
data bi0 cs( 2) / 1.9273379539 93808270e0 /
data bi0 cs( 3) / .2282644586 920301339e0 /
data bi0 cs( 4) / .0130489146 6707290428e0 /
data bi0 cs( 5) / .0004344270 9008164874e0 /
data bi0 cs( 6) / .0000094226 5768600193e0 /
data bi0 cs( 7) / .0000001434 0062895106e0 /
data bi0 cs( 8) / .0000000016 1384906966e0 /
data bi0 cs( 9) / .0000000000 1396650044e0 /
data bi0 cs(10) / .0000000000 0009579451e0 /
data bi0 cs(11) / .0000000000 0000053339e0 /
data bi0 cs(12) / .0000000000 0000000245e0 /
c
data nti0, xsml, xmax / 0, 0., 0. /
c
if (nti0.ne.0) go to 10
nti0 = inits (bi0cs, 12, 0.1*r1mach(3))
xsml = sqrt (4.0*r1mach(3))
xmax = alog (r1mach(2))
c
10 y = abs(x)
if (y.gt.3.0) go to 20
c
besi0 = 1.0
if (y.gt.xsml) besi0 = 2.75 + csevl (y*y/4.5-1.0, bi0cs, nti0)
return
c
20 if (y.gt.xmax) call seteru (34hbesi0 abs(x) so big i0 overflows,
1 34, 1, 2)
c
besi0 = exp(y) * besi0e(x)
c
return
end