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double precision function dbesy1 (x)
c july 1977 edition. w. fullerton, c3, los alamos scientific lab.
double precision x, by1cs(20), ampl, theta, twodpi, xmin, xsml,
1 y, d1mach, dcsevl, dbesj1, dexp, dlog, dsin, dsqrt
external d1mach, dbesj1, dcsevl, initds
c
c series for by1 on the interval 0. to 1.60000e+01
c with weighted error 8.65e-33
c log weighted error 32.06
c significant figures required 32.17
c decimal places required 32.71
c
data by1 cs( 1) / +.3208047100 6119086293 2352018628 015 d-1 /
data by1 cs( 2) / +.1262707897 4335004495 3431725999 727 d+1 /
data by1 cs( 3) / +.6499961899 9231750009 7490637314 144 d-2 /
data by1 cs( 4) / -.8936164528 8605041165 3144160009 712 d-1 /
data by1 cs( 5) / +.1325088122 1757095451 2375510370 043 d-1 /
data by1 cs( 6) / -.8979059119 6483523775 3039508298 105 d-3 /
data by1 cs( 7) / +.3647361487 9583067824 2287368165 349 d-4 /
data by1 cs( 8) / -.1001374381 6660005554 9075523845 295 d-5 /
data by1 cs( 9) / +.1994539657 3901739703 1159372421 243 d-7 /
data by1 cs( 10) / -.3023065601 8033816728 4799332520 743 d-9 /
data by1 cs( 11) / +.3609878156 9478119611 6252914242 474 d-11 /
data by1 cs( 12) / -.3487488297 2875824241 4552947409 066 d-13 /
data by1 cs( 13) / +.2783878971 5591766581 3507698517 333 d-15 /
data by1 cs( 14) / -.1867870968 6194876876 6825352533 333 d-17 /
data by1 cs( 15) / +.1068531533 9116825975 7070336000 000 d-19 /
data by1 cs( 16) / -.5274721956 6844822894 3872000000 000 d-22 /
data by1 cs( 17) / +.2270199403 1556641437 0133333333 333 d-24 /
data by1 cs( 18) / -.8595390353 9452310869 3333333333 333 d-27 /
data by1 cs( 19) / +.2885404379 8337945600 0000000000 000 d-29 /
data by1 cs( 20) / -.8647541138 9371733333 3333333333 333 d-32 /
c
data twodpi / 0.6366197723 6758134307 5535053490 057 d0 /
data nty1, xmin, xsml / 0, 2*0.d0 /
c
if (nty1.ne.0) go to 10
nty1 = initds (by1cs, 20, 0.1*sngl(d1mach(3)))
c
xmin = 1.571d0 * dexp (dmax1(dlog(d1mach(1)), -dlog(d1mach(2))) +
1 0.01d0)
xsml = dsqrt (4.0d0*d1mach(3))
c
10 if (x.le.0.d0) call seteru (29hdbesy1 x is zero or negative, 29,
1 1, 2)
if (x.gt.4.0d0) go to 20
c
if (x.lt.xmin) call seteru (31hdbesy1 x so small y1 overflows,
1 31, 3, 2)
y = 0.d0
if (x.gt.xsml) y = x*x
dbesy1 = twodpi * dlog(0.5d0*x)*dbesj1(x) + (0.5d0 +
1 dcsevl (.125d0*y-1.d0, by1cs, nty1))/x
return
c
20 call d9b1mp (x, ampl, theta)
dbesy1 = ampl * dsin(theta)
return
c
end
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