projects / unix-history / blame
| Commit | Line | Data |
|---|---|---|
| 8daa8d7c DF |
1 | # |
| 2 | # Copyright (c) 1980 Regents of the University of California. | |
| 3 | # All rights reserved. The Berkeley software License Agreement | |
| 4 | # specifies the terms and conditions for redistribution. | |
| 5 | # | |
| 6 | # @(#)cbrt.s 5.1 (Berkeley) %G% | |
| 7 | # | |
| 8 | # | |
| 975e13e8 DF |
9 | # double cbrt(arg) |
| 10 | # double arg | |
| 11 | # no error exits | |
| 12 | #method: range reduction to [1/8,1], poly appox, newtons method | |
| 13 | # J F Jarvis, August 10,1978 | |
| 14 | .globl _cbrt | |
| 15 | .text | |
| 16 | .align 1 | |
| 17 | _cbrt: | |
| 18 | .word 0x00c0 | |
| 19 | bispsw $0xe0 | |
| 20 | clrl r3 | |
| 21 | movd 4(ap),r4 | |
| 22 | jgtr range | |
| 23 | jeql retz | |
| 24 | mnegd r4,r4 # |arg| in r0,r1 | |
| 25 | movl $0x100,r3 # sign bit of result | |
| 26 | range: | |
| 27 | extzv $7,$8,r4,r6 | |
| 28 | insv $128,$7,$8,r4 # 0.5<= frac: r4,r5 <1.0 | |
| 29 | clrl r7 | |
| 30 | ediv $3,r6,r6,r7 # r6= expnt/3; r7= expnt%3 | |
| 31 | addb2 $86,r6 | |
| 32 | bisl2 r3,r6 # sign,exponent of result | |
| 33 | polyf r4,$3,pcoef # initial estimate is Hart&Cheney CBRT 0642 | |
| 34 | # D=4.1 | |
| 35 | muld3 r0,r0,r2 # Newtons method, iteration 1, H&C 6.1.10 | |
| 36 | divd3 r2,r4,r2 | |
| 37 | subd3 r2,r0,r2 | |
| 38 | muld2 third,r2 | |
| 39 | subd2 r2,r0 # D=8.2 | |
| 40 | muld3 r0,r0,r2 # iteration 2 | |
| 41 | divd3 r2,r4,r2 | |
| 42 | subd3 r2,r0,r2 | |
| 43 | muld2 third,r2 | |
| 44 | subd2 r2,r0 | |
| 45 | muld2 hc[r7],r0 # set range | |
| 46 | insv r6,$7,$9,r0 # set sign,exponent | |
| 47 | ret | |
| 48 | retz: | |
| 49 | clrd r0 | |
| 50 | ret | |
| 51 | .data | |
| 52 | .align 2 | |
| 53 | third: .double 0d0.33333333333333333333e+0 | |
| 54 | hc: | |
| 55 | .double 0d1.25992104989487316476e+0 | |
| 56 | .double 0d1.58740105196819947475e+0 | |
| 57 | .double 0d1.0e+0 | |
| 58 | pcoef: | |
| 59 | .float 0f0.1467073818e+0 | |
| 60 | .float 0f-0.5173964673e+0 | |
| 61 | .float 0f0.9319858515e+0 | |
| 62 | .float 0f0.4387762363e+0 |