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fvn_fnlib/dlnrel.f
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double precision function dlnrel (x)
c june 1977 edition. w. fullerton, c3, los alamos scientific lab.
double precision alnrcs(43), x, xmin, dcsevl, d1mach,
1 dlog, dsqrt
external d1mach, dcsevl, initds
c
c series for alnr on the interval -3.75000e-01 to 3.75000e-01
c with weighted error 6.35e-32
c log weighted error 31.20
c significant figures required 30.93
c decimal places required 32.01
c
data alnrcs( 1) / +.1037869356 2743769800 6862677190 98 d+1 /
data alnrcs( 2) / -.1336430150 4908918098 7660415531 33 d+0 /
data alnrcs( 3) / +.1940824913 5520563357 9261993747 50 d-1 /
data alnrcs( 4) / -.3010755112 7535777690 3765377765 92 d-2 /
data alnrcs( 5) / +.4869461479 7154850090 4563665091 37 d-3 /
data alnrcs( 6) / -.8105488189 3175356066 8099430086 22 d-4 /
data alnrcs( 7) / +.1377884779 9559524782 9382514960 59 d-4 /
data alnrcs( 8) / -.2380221089 4358970251 3699929149 35 d-5 /
data alnrcs( 9) / +.4164041621 3865183476 3918599019 89 d-6 /
data alnrcs( 10) / -.7359582837 8075994984 2668370319 98 d-7 /
data alnrcs( 11) / +.1311761187 6241674949 1522943450 11 d-7 /
data alnrcs( 12) / -.2354670931 7742425136 6960923301 75 d-8 /
data alnrcs( 13) / +.4252277327 6034997775 6380529625 67 d-9 /
data alnrcs( 14) / -.7719089413 4840796826 1081074933 00 d-10 /
data alnrcs( 15) / +.1407574648 1359069909 2153564721 91 d-10 /
data alnrcs( 16) / -.2576907205 8024680627 5370786275 84 d-11 /
data alnrcs( 17) / +.4734240666 6294421849 1543950059 38 d-12 /
data alnrcs( 18) / -.8724901267 4742641745 3012632926 75 d-13 /
data alnrcs( 19) / +.1612461490 2740551465 7398331191 15 d-13 /
data alnrcs( 20) / -.2987565201 5665773006 7107924168 15 d-14 /
data alnrcs( 21) / +.5548070120 9082887983 0413216972 79 d-15 /
data alnrcs( 22) / -.1032461915 8271569595 1413339619 32 d-15 /
data alnrcs( 23) / +.1925023920 3049851177 8785032448 68 d-16 /
data alnrcs( 24) / -.3595507346 5265150011 1897078442 66 d-17 /
data alnrcs( 25) / +.6726454253 7876857892 1945742267 73 d-18 /
data alnrcs( 26) / -.1260262416 8735219252 0824256375 46 d-18 /
data alnrcs( 27) / +.2364488440 8606210044 9161589555 19 d-19 /
data alnrcs( 28) / -.4441937705 0807936898 8783891797 33 d-20 /
data alnrcs( 29) / +.8354659446 4034259016 2412939946 66 d-21 /
data alnrcs( 30) / -.1573155941 6479562574 8992535210 66 d-21 /
data alnrcs( 31) / +.2965312874 0247422686 1543697066 66 d-22 /
data alnrcs( 32) / -.5594958348 1815947292 1560132266 66 d-23 /
data alnrcs( 33) / +.1056635426 8835681048 1872841386 66 d-23 /
data alnrcs( 34) / -.1997248368 0670204548 3149994666 66 d-24 /
data alnrcs( 35) / +.3778297781 8839361421 0498559999 99 d-25 /
data alnrcs( 36) / -.7153158688 9081740345 0381653333 33 d-26 /
data alnrcs( 37) / +.1355248846 3674213646 5020245333 33 d-26 /
data alnrcs( 38) / -.2569467304 8487567430 0798293333 33 d-27 /
data alnrcs( 39) / +.4874775606 6216949076 4595199999 99 d-28 /
data alnrcs( 40) / -.9254211253 0849715321 1323733333 33 d-29 /
data alnrcs( 41) / +.1757859784 1760239233 2697600000 00 d-29 /
data alnrcs( 42) / -.3341002667 7731010351 3770666666 66 d-30 /
data alnrcs( 43) / +.6353393618 0236187354 1802666666 66 d-31 /
c
data nlnrel, xmin / 0, 0.d0 /
c
if (nlnrel.ne.0) go to 10
nlnrel = initds (alnrcs, 43, 0.1*sngl(d1mach(3)))
xmin = -1.0d0 + dsqrt(d1mach(4))
c
10 if (x.le.(-1.d0)) call seteru (18hdlnrel x is le -1, 18, 2, 2)
if (x.lt.xmin) call seteru (
1 54hdlnrel answer lt half precision because x too near -1, 54,
2 1, 1)
c
if (dabs(x).le.0.375d0) dlnrel = x*(1.d0 -
1 x*dcsevl (x/.375d0, alnrcs, nlnrel))
c
if (dabs(x).gt.0.375d0) dlnrel = dlog (1.0d0+x)
c
return
end
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