| 1 | /* e_j0f.c -- float version of e_j0.c. |
|---|---|
| 2 | * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. |
| 3 | */ |
| 4 | |
| 5 | /* |
| 6 | * ==================================================== |
| 7 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
| 8 | * |
| 9 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
| 10 | * Permission to use, copy, modify, and distribute this |
| 11 | * software is freely granted, provided that this notice |
| 12 | * is preserved. |
| 13 | * ==================================================== |
| 14 | */ |
| 15 | |
| 16 | #include <math.h> |
| 17 | #include <math-barriers.h> |
| 18 | #include <math_private.h> |
| 19 | #include <fenv_private.h> |
| 20 | #include <libm-alias-finite.h> |
| 21 | #include <reduce_aux.h> |
| 22 | |
| 23 | static float pzerof(float), qzerof(float); |
| 24 | |
| 25 | static const float |
| 26 | huge = 1e30, |
| 27 | one = 1.0, |
| 28 | invsqrtpi= 5.6418961287e-01, /* 0x3f106ebb */ |
| 29 | tpi = 6.3661974669e-01, /* 0x3f22f983 */ |
| 30 | /* R0/S0 on [0, 2.00] */ |
| 31 | R02 = 1.5625000000e-02, /* 0x3c800000 */ |
| 32 | R03 = -1.8997929874e-04, /* 0xb947352e */ |
| 33 | R04 = 1.8295404516e-06, /* 0x35f58e88 */ |
| 34 | R05 = -4.6183270541e-09, /* 0xb19eaf3c */ |
| 35 | S01 = 1.5619102865e-02, /* 0x3c7fe744 */ |
| 36 | S02 = 1.1692678527e-04, /* 0x38f53697 */ |
| 37 | S03 = 5.1354652442e-07, /* 0x3509daa6 */ |
| 38 | S04 = 1.1661400734e-09; /* 0x30a045e8 */ |
| 39 | |
| 40 | static const float zero = 0.0; |
| 41 | |
| 42 | /* This is the nearest approximation of the first zero of j0. */ |
| 43 | #define FIRST_ZERO_J0 0xf.26247p-28f |
| 44 | |
| 45 | #define SMALL_SIZE 64 |
| 46 | |
| 47 | /* The following table contains successive zeros of j0 and degree-3 |
| 48 | polynomial approximations of j0 around these zeros: Pj[0] for the first |
| 49 | zero (2.40482), Pj[1] for the second one (5.520078), and so on. |
| 50 | Each line contains: |
| 51 | {x0, xmid, x1, p0, p1, p2, p3} |
| 52 | where [x0,x1] is the interval around the zero, xmid is the binary32 number |
| 53 | closest to the zero, and p0+p1*x+p2*x^2+p3*x^3 is the approximation |
| 54 | polynomial. Each polynomial was generated using Sollya on the interval |
| 55 | [x0,x1] around the corresponding zero where the error exceeds 9 ulps |
| 56 | for the alternate code. Degree 3 is enough to get an error <= 9 ulps. |
| 57 | */ |
| 58 | static const float Pj[SMALL_SIZE][7] = { |
| 59 | /* The following polynomial was optimized by hand with respect to the one |
| 60 | generated by Sollya, to ensure the maximal error is at most 9 ulps, |
| 61 | both if the polynomial is evaluated with fma or not. */ |
| 62 | { 0x1.31e5c4p+1, 0x1.33d152p+1, 0x1.3b58dep+1, 0xf.2623fp-28, |
| 63 | -0x8.4e6d7p-4, 0x1.ba2aaap-4, 0xe.4b9ap-8 }, /* 0 */ |
| 64 | { 0x1.60eafap+2, 0x1.6148f6p+2, 0x1.62955cp+2, 0x6.9205fp-28, |
| 65 | 0x5.71b98p-4, -0x7.e3e798p-8, -0xd.87d1p-8 }, /* 1 */ |
| 66 | { 0x1.14cde2p+3, 0x1.14eb56p+3, 0x1.1525c6p+3, 0x1.bcc1cap-24, |
| 67 | -0x4.57de6p-4, 0x4.03e7cp-8, 0xb.39a37p-8 }, /* 2 */ |
| 68 | { 0x1.7931d8p+3, 0x1.79544p+3, 0x1.7998d6p+3, -0xf.2976fp-32, |
| 69 | 0x3.b827ccp-4, -0x2.8603ep-8, -0x9.bf49bp-8 }, /* 3 */ |
| 70 | { 0x1.ddb6d4p+3, 0x1.ddca14p+3, 0x1.ddf0c8p+3, -0x1.bd67d8p-28, |
| 71 | -0x3.4e03ap-4, 0x1.c562a2p-8, 0x8.90ec2p-8 }, /* 4 */ |
| 72 | { 0x1.2118e4p+4, 0x1.212314p+4, 0x1.21375p+4, 0x1.62209cp-28, |
| 73 | 0x3.00efecp-4, -0x1.5458dap-8, -0x8.10063p-8 }, /* 5 */ |
| 74 | { 0x1.535d28p+4, 0x1.5362dep+4, 0x1.536e48p+4, -0x2.853f74p-24, |
| 75 | -0x2.c5b274p-4, 0x1.0b9db4p-8, 0x7.8c3578p-8 }, /* 6 */ |
| 76 | { 0x1.859ddp+4, 0x1.85a3bap+4, 0x1.85aff4p+4, 0x2.19ed1cp-24, |
| 77 | 0x2.96545cp-4, -0xd.997e6p-12, -0x6.d9af28p-8 }, /* 7 */ |
| 78 | { 0x1.b7decap+4, 0x1.b7e54ap+4, 0x1.b7f038p+4, 0xe.959aep-28, |
| 79 | -0x2.6f5594p-4, 0xb.538dp-12, 0x7.003ea8p-8 }, /* 8 */ |
| 80 | { 0x1.ea21c6p+4, 0x1.ea275ap+4, 0x1.ea337ap+4, 0x2.0c3964p-24, |
| 81 | 0x2.4e80fcp-4, -0x9.a2216p-12, -0x6.61e0a8p-8 }, /* 9 */ |
| 82 | { 0x1.0e3316p+5, 0x1.0e34e2p+5, 0x1.0e379ap+5, -0x3.642554p-24, |
| 83 | -0x2.325e48p-4, 0x8.4f49cp-12, 0x7.d37c3p-8 }, /* 10 */ |
| 84 | { 0x1.275456p+5, 0x1.275638p+5, 0x1.2759e2p+5, 0x1.6c015ap-24, |
| 85 | 0x2.19e7d8p-4, -0x7.4c1bf8p-12, -0x4.af7ef8p-8 }, /* 11 */ |
| 86 | { 0x1.4075ecp+5, 0x1.4077a8p+5, 0x1.407b96p+5, -0x4.b18c9p-28, |
| 87 | -0x2.046174p-4, 0x6.705618p-12, 0x5.f2d28p-8 }, /* 12 */ |
| 88 | { 0x1.59973p+5, 0x1.59992cp+5, 0x1.599b2ap+5, -0x1.8b8792p-24, |
| 89 | 0x1.f13fbp-4, -0x5.c14938p-12, -0x5.73e0cp-8 }, /* 13 */ |
| 90 | { 0x1.72b958p+5, 0x1.72bacp+5, 0x1.72bc5ap+5, 0x3.a26e0cp-24, |
| 91 | -0x1.e018dap-4, 0x5.30e8dp-12, 0x2.81099p-8 }, /* 14 */ |
| 92 | { 0x1.8bdb4ap+5, 0x1.8bdc62p+5, 0x1.8bde7ep+5, -0x2.18fabcp-24, |
| 93 | 0x1.d09b22p-4, -0x4.b0b688p-12, -0x5.5fd308p-8 }, /* 15 */ |
| 94 | { 0x1.a4fcecp+5, 0x1.a4fe0ep+5, 0x1.a50042p+5, 0x3.2370e8p-24, |
| 95 | -0x1.c28614p-4, 0x4.4647e8p-12, 0x5.68a28p-8 }, /* 16 */ |
| 96 | { 0x1.be1ebcp+5, 0x1.be1fc4p+5, 0x1.be21fp+5, -0x5.9eae3p-28, |
| 97 | 0x1.b5a622p-4, -0x3.eb9054p-12, -0x5.12d8cp-8 }, /* 17 */ |
| 98 | { 0x1.d7405p+5, 0x1.d7418p+5, 0x1.d74294p+5, 0x2.9fa1e8p-24, |
| 99 | -0x1.a9d184p-4, 0x3.9d1e7p-12, 0x4.33d058p-8 }, /* 18 */ |
| 100 | { 0x1.f0624p+5, 0x1.f06344p+5, 0x1.f0645ep+5, 0x9.9ac67p-28, |
| 101 | 0x1.9ee5eep-4, -0x3.5816e8p-12, -0x2.6e5004p-8 }, /* 19 */ |
| 102 | { 0x1.04c22ep+6, 0x1.04c286p+6, 0x1.04c316p+6, 0xd.6ab94p-28, |
| 103 | -0x1.94c6f6p-4, 0x3.174efcp-12, 0x7.9a092p-8 }, /* 20 */ |
| 104 | { 0x1.1153p+6, 0x1.11536cp+6, 0x1.11541p+6, -0x4.4cb2d8p-24, |
| 105 | 0x1.8b5cccp-4, -0x2.e3c238p-12, -0x4.e5437p-8 }, /* 21 */ |
| 106 | { 0x1.1de3d8p+6, 0x1.1de456p+6, 0x1.1de4dap+6, -0x4.4aa8c8p-24, |
| 107 | -0x1.829356p-4, 0x2.b45124p-12, 0x5.baf638p-8 }, /* 22 */ |
| 108 | { 0x1.2a74f8p+6, 0x1.2a754p+6, 0x1.2a75bp+6, 0x2.077c38p-24, |
| 109 | 0x1.7a597ep-4, -0x2.8a0414p-12, -0x2.838d3p-8 }, /* 23 */ |
| 110 | { 0x1.3705d4p+6, 0x1.37062cp+6, 0x1.3706b2p+6, -0x2.6a6cd8p-24, |
| 111 | -0x1.72a09ap-4, 0x2.623a3cp-12, 0x5.5256a8p-8 }, /* 24 */ |
| 112 | { 0x1.4396dp+6, 0x1.439718p+6, 0x1.43976ep+6, -0x5.08287p-24, |
| 113 | 0x1.6b5c06p-4, -0x2.3da154p-12, -0x7.a2254p-8 }, /* 25 */ |
| 114 | { 0x1.5027acp+6, 0x1.502808p+6, 0x1.50288cp+6, -0x3.4598dcp-24, |
| 115 | -0x1.6480c4p-4, 0x2.1cb944p-12, 0x7.27c77p-8 }, /* 26 */ |
| 116 | { 0x1.5cb89ap+6, 0x1.5cb8f8p+6, 0x1.5cb97ep+6, 0x5.4e74bp-24, |
| 117 | 0x1.5e0544p-4, -0x2.00b158p-12, -0x5.9bc4a8p-8 }, /* 27 */ |
| 118 | { 0x1.69498cp+6, 0x1.6949e8p+6, 0x1.694a42p+6, -0x2.05751cp-24, |
| 119 | -0x1.57e12p-4, 0x1.e78edcp-12, 0x9.9667dp-8 }, /* 28 */ |
| 120 | { 0x1.75da7ep+6, 0x1.75dadap+6, 0x1.75db3p+6, 0x4.c5e278p-24, |
| 121 | 0x1.520ceep-4, -0x1.d0127cp-12, -0xd.62681p-8 }, /* 29 */ |
| 122 | { 0x1.826b7ep+6, 0x1.826bccp+6, 0x1.826c2cp+6, -0x3.50e62cp-24, |
| 123 | -0x1.4c822p-4, 0x1.ba5832p-12, -0x1.eb2ee2p-8 }, /* 30 */ |
| 124 | { 0x1.8efc84p+6, 0x1.8efcbep+6, 0x1.8efd16p+6, -0x1.c39f38p-24, |
| 125 | 0x1.473ae6p-4, -0x1.a616c8p-12, 0xf.f352ap-12 }, /* 31 */ |
| 126 | { 0x1.9b8d84p+6, 0x1.9b8db2p+6, 0x1.9b8e7p+6, -0x1.9245b6p-28, |
| 127 | -0x1.42320ap-4, 0x1.932a04p-12, 0x2.dc113cp-8 }, /* 32 */ |
| 128 | { 0x1.a81e72p+6, 0x1.a81ea6p+6, 0x1.a81f04p+6, -0x1.0acf8p-24, |
| 129 | 0x1.3d62e6p-4, -0x1.7c4b14p-12, -0x1.cfc5c2p-4 }, /* 33 */ |
| 130 | { 0x1.b4af6ap+6, 0x1.b4af9ap+6, 0x1.b4afeep+6, 0x4.cd92d8p-24, |
| 131 | -0x1.38c94ap-4, 0x1.643154p-12, 0x1.4c2a06p-4 }, /* 34 */ |
| 132 | { 0x1.c1406p+6, 0x1.c1409p+6, 0x1.c140cp+6, -0x1.37bf8ap-24, |
| 133 | 0x1.34617p-4, -0x1.5f504ap-12, -0x1.e2d324p-4 }, /* 35 */ |
| 134 | { 0x1.cdd154p+6, 0x1.cdd186p+6, 0x1.cdd1eap+6, -0x1.8f62dep-28, |
| 135 | -0x1.3027fp-4, 0x1.534a02p-12, 0x2.c7f144p-12 }, /* 36 */ |
| 136 | { 0x1.da6248p+6, 0x1.da627cp+6, 0x1.da62e6p+6, -0x9.81e79p-28, |
| 137 | 0x1.2c19b4p-4, -0x1.4b8288p-12, 0x7.2d8bap-8 }, /* 37 */ |
| 138 | { 0x1.e6f33ep+6, 0x1.e6f372p+6, 0x1.e6f3a8p+6, 0x3.103b3p-24, |
| 139 | -0x1.2833eep-4, 0x1.36f4d2p-12, 0x9.29f91p-8 }, /* 38 */ |
| 140 | { 0x1.f38434p+6, 0x1.f3846ap+6, 0x1.f384d8p+6, 0x2.07b058p-24, |
| 141 | 0x1.24740ap-4, -0x1.2ee58ap-12, 0xd.f1393p-12 }, /* 39 */ |
| 142 | { 0x1.000a98p+7, 0x1.000abp+7, 0x1.000ac8p+7, 0x3.87576cp-24, |
| 143 | -0x1.20d7b6p-4, 0x1.2083e2p-12, 0x3.9a7aap-8 }, /* 40 */ |
| 144 | { 0x1.06531p+7, 0x1.06532cp+7, 0x1.065348p+7, -0x1.691ecp-24, |
| 145 | 0x1.1d5ccap-4, -0x1.166726p-12, -0x1.e4af48p-8 }, /* 41 */ |
| 146 | { 0x1.0c9b9ap+7, 0x1.0c9ba8p+7, 0x1.0c9bbep+7, 0x9.b406dp-28, |
| 147 | -0x1.1a015p-4, 0x1.038f9cp-12, -0x4.021058p-4 }, /* 42 */ |
| 148 | { 0x1.12e412p+7, 0x1.12e424p+7, 0x1.12e436p+7, -0xf.bfd8fp-28, |
| 149 | 0x1.16c37ap-4, -0x1.039edep-12, 0x1.f0033p-4 }, /* 43 */ |
| 150 | { 0x1.192c92p+7, 0x1.192cap+7, 0x1.192cb6p+7, 0x2.6d50c8p-24, |
| 151 | -0x1.13a19ep-4, 0xf.9df8ap-16, 0x4.ecd978p-8 }, /* 44 */ |
| 152 | { 0x1.1f7512p+7, 0x1.1f751cp+7, 0x1.1f753ap+7, -0x4.d475c8p-24, |
| 153 | 0x1.109a32p-4, -0x1.04fb3ap-12, -0xd.c271p-12 }, /* 45 */ |
| 154 | { 0x1.25bd8ep+7, 0x1.25bd98p+7, 0x1.25bdap+7, 0x8.1982p-24, |
| 155 | -0x1.0dabc8p-4, 0xe.88eabp-16, -0x4.ed75dp-4 }, /* 46 */ |
| 156 | { 0x1.2c060cp+7, 0x1.2c0616p+7, 0x1.2c0644p+7, 0x4.864518p-24, |
| 157 | 0x1.0ad51p-4, -0xe.27196p-16, 0xb.97a3ep-8 }, /* 47 */ |
| 158 | { 0x1.324e86p+7, 0x1.324e92p+7, 0x1.324e9ep+7, 0x6.8917a8p-28, |
| 159 | -0x1.0814d4p-4, 0xd.4fe7ep-16, -0x6.8d8d6p-4 }, /* 48 */ |
| 160 | { 0x1.389702p+7, 0x1.38970ep+7, 0x1.389728p+7, -0x5.fa18fp-24, |
| 161 | 0x1.0569fp-4, -0xd.5b0d4p-16, 0x1.50353ap-4 }, /* 49 */ |
| 162 | { 0x1.3edf84p+7, 0x1.3edf8cp+7, 0x1.3edfaap+7, -0x4.0e5c98p-24, |
| 163 | -0x1.02d354p-4, 0xb.7b255p-16, 0x7.8a916p-4 }, /* 50 */ |
| 164 | { 0x1.4527fp+7, 0x1.452808p+7, 0x1.452812p+7, -0x2.c3ddbp-24, |
| 165 | 0x1.005004p-4, -0xd.7729cp-16, -0x3.bcc354p-8 }, /* 51 */ |
| 166 | { 0x1.4b7076p+7, 0x1.4b7086p+7, 0x1.4b70a4p+7, -0x5.d052p-24, |
| 167 | -0xf.ddf16p-8, 0xc.318c1p-16, 0x5.7947p-8 }, /* 52 */ |
| 168 | { 0x1.51b8f4p+7, 0x1.51b902p+7, 0x1.51b90ep+7, -0x2.0b97dcp-24, |
| 169 | 0xf.b7fafp-8, -0xc.1429dp-16, -0x3.43c36p-4 }, /* 53 */ |
| 170 | { 0x1.580168p+7, 0x1.58018p+7, 0x1.580188p+7, -0x5.4aab5p-24, |
| 171 | -0xf.930fep-8, 0xa.ecc24p-16, 0x9.c62cdp-12 }, /* 54 */ |
| 172 | { 0x1.5e49eap+7, 0x1.5e49fcp+7, 0x1.5e4a12p+7, -0x3.6dadd8p-24, |
| 173 | 0xf.6f245p-8, -0xb.6816cp-16, 0xa.d731ap-8 }, /* 55 */ |
| 174 | { 0x1.649272p+7, 0x1.64927ap+7, 0x1.64929p+7, -0x2.d7e038p-24, |
| 175 | -0xf.4c2cep-8, 0xb.118bep-16, 0xb.69a4ep-8 }, /* 56 */ |
| 176 | { 0x1.6adae6p+7, 0x1.6adaf6p+7, 0x1.6adb04p+7, -0x6.977a1p-24, |
| 177 | 0xf.2a1fp-8, -0xa.a8911p-16, -0x4.bf6d2p-8 }, /* 57 */ |
| 178 | { 0x1.712366p+7, 0x1.712374p+7, 0x1.71238ep+7, 0x1.3cc95ep-24, |
| 179 | -0xf.08f0ap-8, 0x9.f0858p-16, 0x1.77f7f4p-4 }, /* 58 */ |
| 180 | { 0x1.776beap+7, 0x1.776bf2p+7, 0x1.776bfap+7, 0x3.a4921p-24, |
| 181 | 0xe.e8986p-8, -0xa.39dfp-16, -0x6.7ba3dp-4 }, /* 59 */ |
| 182 | { 0x1.7db464p+7, 0x1.7db46ep+7, 0x1.7db476p+7, 0x6.b45a7p-24, |
| 183 | -0xe.c90d8p-8, 0xa.e586fp-16, -0x1.d66becp-4 }, /* 60 */ |
| 184 | { 0x1.83fce2p+7, 0x1.83fcecp+7, 0x1.83fd0ep+7, -0x2.8f34a4p-24, |
| 185 | 0xe.aa478p-8, -0x9.810bp-16, -0x3.a5f3fcp-8 }, /* 61 */ |
| 186 | { 0x1.8a455cp+7, 0x1.8a456ap+7, 0x1.8a4588p+7, -0x1.325968p-24, |
| 187 | -0xe.8c3eap-8, 0x9.0a765p-16, 0x1.29a54ap-4 }, /* 62 */ |
| 188 | { 0x1.908dd8p+7, 0x1.908de8p+7, 0x1.908df4p+7, 0x4.96b808p-24, |
| 189 | 0xe.6eeb5p-8, -0x9.0251bp-16, 0x1.41a488p-4 }, /* 63 */ |
| 190 | }; |
| 191 | |
| 192 | /* Formula page 5 of https://www.cl.cam.ac.uk/~jrh13/papers/bessel.pdf: |
| 193 | j0f(x) ~ sqrt(2/(pi*x))*beta0(x)*cos(x-pi/4-alpha0(x)) |
| 194 | where beta0(x) = 1 - 1/(16*x^2) + 53/(512*x^4) |
| 195 | and alpha0(x) = 1/(8*x) - 25/(384*x^3). */ |
| 196 | static float |
| 197 | j0f_asympt (float x) |
| 198 | { |
| 199 | /* The following code fails to give an error <= 9 ulps in only two cases, |
| 200 | for which we tabulate the result. */ |
| 201 | if (x == 0x1.4665d2p+24f) |
| 202 | return 0xa.50206p-52f; |
| 203 | if (x == 0x1.a9afdep+7f) |
| 204 | return 0xf.47039p-28f; |
| 205 | double y = 1.0 / (double) x; |
| 206 | double y2 = y * y; |
| 207 | double beta0 = 1.0f + y2 * (-0x1p-4f + 0x1.a8p-4 * y2); |
| 208 | double alpha0 = y * (0x2p-4 - 0x1.0aaaaap-4 * y2); |
| 209 | double h; |
| 210 | int n; |
| 211 | h = reduce_aux (x, &n, alpha0); |
| 212 | /* Now x - pi/4 - alpha0 = h + n*pi/2 mod (2*pi). */ |
| 213 | float xr = (float) h; |
| 214 | n = n & 3; |
| 215 | float cst = 0xc.c422ap-4; /* sqrt(2/pi) rounded to nearest */ |
| 216 | float t = cst / sqrtf (x) * (float) beta0; |
| 217 | if (n == 0) |
| 218 | return t * __cosf (xr); |
| 219 | else if (n == 2) /* cos(x+pi) = -cos(x) */ |
| 220 | return -t * __cosf (xr); |
| 221 | else if (n == 1) /* cos(x+pi/2) = -sin(x) */ |
| 222 | return -t * __sinf (xr); |
| 223 | else /* cos(x+3pi/2) = sin(x) */ |
| 224 | return t * __sinf (xr); |
| 225 | } |
| 226 | |
| 227 | /* Special code for x near a root of j0. |
| 228 | z is the value computed by the generic code. |
| 229 | For small x, we use a polynomial approximating j0 around its root. |
| 230 | For large x, we use an asymptotic formula (j0f_asympt). */ |
| 231 | static float |
| 232 | j0f_near_root (float x, float z) |
| 233 | { |
| 234 | float index_f; |
| 235 | int index; |
| 236 | |
| 237 | index_f = roundf ((x - FIRST_ZERO_J0) / (float) M_PI); |
| 238 | /* j0f_asympt fails to give an error <= 9 ulps for x=0x1.324e92p+7 |
| 239 | (index 48) thus we can't reduce SMALL_SIZE below 49. */ |
| 240 | if (index_f >= SMALL_SIZE) |
| 241 | return j0f_asympt (x); |
| 242 | index = (int) index_f; |
| 243 | const float *p = Pj[index]; |
| 244 | float x0 = p[0]; |
| 245 | float x1 = p[2]; |
| 246 | /* If not in the interval [x0,x1] around xmid, we return the value z. */ |
| 247 | if (! (x0 <= x && x <= x1)) |
| 248 | return z; |
| 249 | float xmid = p[1]; |
| 250 | float y = x - xmid; |
| 251 | return p[3] + y * (p[4] + y * (p[5] + y * p[6])); |
| 252 | } |
| 253 | |
| 254 | float |
| 255 | __ieee754_j0f(float x) |
| 256 | { |
| 257 | float z, s,c,ss,cc,r,u,v; |
| 258 | int32_t hx,ix; |
| 259 | |
| 260 | GET_FLOAT_WORD(hx,x); |
| 261 | ix = hx&0x7fffffff; |
| 262 | if(ix>=0x7f800000) return one/(x*x); |
| 263 | x = fabsf(x); |
| 264 | if(ix >= 0x40000000) { /* |x| >= 2.0 */ |
| 265 | SET_RESTORE_ROUNDF (FE_TONEAREST); |
| 266 | __sincosf (x, &s, &c); |
| 267 | ss = s-c; |
| 268 | cc = s+c; |
| 269 | if (ix >= 0x7f000000) |
| 270 | /* x >= 2^127: use asymptotic expansion. */ |
| 271 | return j0f_asympt (x); |
| 272 | /* Now we are sure that x+x cannot overflow. */ |
| 273 | z = -__cosf(x+x); |
| 274 | if ((s*c)<zero) cc = z/ss; |
| 275 | else ss = z/cc; |
| 276 | /* |
| 277 | * j0(x) = 1/sqrt(pi) * (P(0,x)*cc - Q(0,x)*ss) / sqrt(x) |
| 278 | * y0(x) = 1/sqrt(pi) * (P(0,x)*ss + Q(0,x)*cc) / sqrt(x) |
| 279 | */ |
| 280 | if (ix <= 0x5c000000) |
| 281 | { |
| 282 | u = pzerof(x); v = qzerof(x); |
| 283 | cc = u*cc-v*ss; |
| 284 | } |
| 285 | z = (invsqrtpi * cc) / sqrtf(x); |
| 286 | /* The following threshold is optimal: for x=0x1.3b58dep+1 |
| 287 | and rounding upwards, |cc|=0x1.579b26p-4 and z is 10 ulps |
| 288 | far from the correctly rounded value. */ |
| 289 | float threshold = 0x1.579b26p-4; |
| 290 | if (fabsf (cc) > threshold) |
| 291 | return z; |
| 292 | else |
| 293 | return j0f_near_root (x, z); |
| 294 | } |
| 295 | if(ix<0x39000000) { /* |x| < 2**-13 */ |
| 296 | math_force_eval(huge+x); /* raise inexact if x != 0 */ |
| 297 | if(ix<0x32000000) return one; /* |x|<2**-27 */ |
| 298 | else return one - (float)0.25*x*x; |
| 299 | } |
| 300 | z = x*x; |
| 301 | r = z*(R02+z*(R03+z*(R04+z*R05))); |
| 302 | s = one+z*(S01+z*(S02+z*(S03+z*S04))); |
| 303 | if(ix < 0x3F800000) { /* |x| < 1.00 */ |
| 304 | return one + z*((float)-0.25+(r/s)); |
| 305 | } else { |
| 306 | u = (float)0.5*x; |
| 307 | return((one+u)*(one-u)+z*(r/s)); |
| 308 | } |
| 309 | } |
| 310 | libm_alias_finite (__ieee754_j0f, __j0f) |
| 311 | |
| 312 | static const float |
| 313 | u00 = -7.3804296553e-02, /* 0xbd9726b5 */ |
| 314 | u01 = 1.7666645348e-01, /* 0x3e34e80d */ |
| 315 | u02 = -1.3818567619e-02, /* 0xbc626746 */ |
| 316 | u03 = 3.4745343146e-04, /* 0x39b62a69 */ |
| 317 | u04 = -3.8140706238e-06, /* 0xb67ff53c */ |
| 318 | u05 = 1.9559013964e-08, /* 0x32a802ba */ |
| 319 | u06 = -3.9820518410e-11, /* 0xae2f21eb */ |
| 320 | v01 = 1.2730483897e-02, /* 0x3c509385 */ |
| 321 | v02 = 7.6006865129e-05, /* 0x389f65e0 */ |
| 322 | v03 = 2.5915085189e-07, /* 0x348b216c */ |
| 323 | v04 = 4.4111031494e-10; /* 0x2ff280c2 */ |
| 324 | |
| 325 | /* This is the nearest approximation of the first zero of y0. */ |
| 326 | #define FIRST_ZERO_Y0 0xe.4c166p-4f |
| 327 | |
| 328 | /* The following table contains successive zeros of y0 and degree-3 |
| 329 | polynomial approximations of y0 around these zeros: Py[0] for the first |
| 330 | zero (0.89358), Py[1] for the second one (3.957678), and so on. |
| 331 | Each line contains: |
| 332 | {x0, xmid, x1, p0, p1, p2, p3} |
| 333 | where [x0,x1] is the interval around the zero, xmid is the binary32 number |
| 334 | closest to the zero, and p0+p1*x+p2*x^2+p3*x^3 is the approximation |
| 335 | polynomial. Each polynomial was generated using Sollya on the interval |
| 336 | [x0,x1] around the corresponding zero where the error exceeds 9 ulps |
| 337 | for the alternate code. Degree 3 is enough, except for index 0 where we |
| 338 | use degree 5, and the coefficients of degree 4 and 5 are hard-coded in |
| 339 | y0f_near_root. |
| 340 | */ |
| 341 | static const float Py[SMALL_SIZE][7] = { |
| 342 | { 0x1.a681dap-1, 0x1.c982ecp-1, 0x1.ef6bcap-1, 0x3.274468p-28, |
| 343 | 0xe.121b8p-4, -0x7.df8b3p-4, 0x3.877be4p-4 |
| 344 | /*, -0x3.a46c9p-4, 0x3.735478p-4*/ }, /* 0 */ |
| 345 | { 0x1.f957c6p+1, 0x1.fa9534p+1, 0x1.fd11b2p+1, 0xa.f1f83p-28, |
| 346 | -0x6.70d098p-4, 0xd.04d48p-8, 0xe.f61a9p-8 }, /* 1 */ |
| 347 | { 0x1.c51832p+2, 0x1.c581dcp+2, 0x1.c65164p+2, -0x5.e2a51p-28, |
| 348 | 0x4.cd3328p-4, -0x5.6bbe08p-8, -0xc.46d8p-8 }, /* 2 */ |
| 349 | { 0x1.46fd84p+3, 0x1.471d74p+3, 0x1.475bfcp+3, -0x1.4b0aeep-24, |
| 350 | -0x3.fec6b8p-4, 0x3.2068a4p-8, 0xa.76e2dp-8 }, /* 3 */ |
| 351 | { 0x1.ab7afap+3, 0x1.ab8e1cp+3, 0x1.abb294p+3, -0x8.179d7p-28, |
| 352 | 0x3.7e6544p-4, -0x2.1799fp-8, -0x9.0e1c4p-8 }, /* 4 */ |
| 353 | { 0x1.07f9aap+4, 0x1.0803c8p+4, 0x1.08170cp+4, -0x2.5b8078p-24, |
| 354 | -0x3.24b868p-4, 0x1.8631ecp-8, 0x8.3cb46p-8 }, /* 5 */ |
| 355 | { 0x1.3a38eap+4, 0x1.3a42cep+4, 0x1.3a4d8ap+4, 0x1.cd304ap-28, |
| 356 | 0x2.e189ecp-4, -0x1.2c6954p-8, -0x7.8178ep-8 }, /* 6 */ |
| 357 | { 0x1.6c7d42p+4, 0x1.6c833p+4, 0x1.6c99fp+4, -0x6.c63f1p-28, |
| 358 | -0x2.acc9a8p-4, 0xf.09e31p-12, 0x7.0b5ab8p-8 }, /* 7 */ |
| 359 | { 0x1.9ebec4p+4, 0x1.9ec47p+4, 0x1.9ed016p+4, 0x1.e53838p-24, |
| 360 | 0x2.81f2p-4, -0xc.5ff51p-12, -0x7.05ep-8 }, /* 8 */ |
| 361 | { 0x1.d1008ep+4, 0x1.d10644p+4, 0x1.d11262p+4, 0x1.636feep-24, |
| 362 | -0x2.5e40dcp-4, 0xa.6f81dp-12, 0x5.ff6p-8 }, /* 9 */ |
| 363 | { 0x1.01a27cp+5, 0x1.01a442p+5, 0x1.01a924p+5, -0x4.04e1bp-28, |
| 364 | 0x2.3febd8p-4, -0x8.f11e2p-12, -0x6.0111ap-8 }, /* 10 */ |
| 365 | { 0x1.1ac3bcp+5, 0x1.1ac588p+5, 0x1.1ac912p+5, 0x3.6063d8p-24, |
| 366 | -0x2.25baacp-4, 0x7.c93cdp-12, 0x4.e7577p-8 }, /* 11 */ |
| 367 | { 0x1.33e508p+5, 0x1.33e6ecp+5, 0x1.33ea1ap+5, -0x3.f39ebcp-24, |
| 368 | 0x2.0ed04cp-4, -0x6.d9434p-12, -0x4.fc0b7p-8 }, /* 12 */ |
| 369 | { 0x1.4d0666p+5, 0x1.4d0868p+5, 0x1.4d0c14p+5, -0x4.ea23p-28, |
| 370 | -0x1.fa8b4p-4, 0x6.1470e8p-12, 0x5.97f71p-8 }, /* 13 */ |
| 371 | { 0x1.6628b8p+5, 0x1.6629f4p+5, 0x1.662e0ep+5, -0x3.5df0c8p-24, |
| 372 | 0x1.e8727ep-4, -0x5.76a038p-12, -0x4.ee37c8p-8 }, /* 14 */ |
| 373 | { 0x1.7f4a7cp+5, 0x1.7f4b9p+5, 0x1.7f4daap+5, 0x1.1ef09ep-24, |
| 374 | -0x1.d8293ap-4, 0x4.ed8a28p-12, 0x4.d43708p-8 }, /* 15 */ |
| 375 | { 0x1.986c5cp+5, 0x1.986d38p+5, 0x1.986f6p+5, 0x1.b70cecp-24, |
| 376 | 0x1.c967p-4, -0x4.7a70b8p-12, -0x5.6840e8p-8 }, /* 16 */ |
| 377 | { 0x1.b18dcap+5, 0x1.b18ee8p+5, 0x1.b19122p+5, 0x1.abaadcp-24, |
| 378 | -0x1.bbf246p-4, 0x4.1a35bp-12, 0x3.c2d46p-8 }, /* 17 */ |
| 379 | { 0x1.caaf86p+5, 0x1.cab0a2p+5, 0x1.cab2fep+5, 0x1.63989ep-24, |
| 380 | 0x1.af9cb4p-4, -0x3.c2f2dcp-12, -0x4.cf8108p-8 }, /* 18 */ |
| 381 | { 0x1.e3d146p+5, 0x1.e3d262p+5, 0x1.e3d492p+5, -0x1.68a8ecp-24, |
| 382 | -0x1.a4407ep-4, 0x3.7733ecp-12, 0x5.97916p-8 }, /* 19 */ |
| 383 | { 0x1.fcf316p+5, 0x1.fcf428p+5, 0x1.fcf59ap+5, 0x1.e1bb5p-24, |
| 384 | 0x1.99be74p-4, -0x3.37210cp-12, -0x5.d19bf8p-8 }, /* 20 */ |
| 385 | { 0x1.0b0a7cp+6, 0x1.0b0afap+6, 0x1.0b0b9cp+6, -0x5.5bbcfp-24, |
| 386 | -0x1.8ffc9ap-4, 0x2.ffe638p-12, 0x2.ed28e8p-8 }, /* 21 */ |
| 387 | { 0x1.179b66p+6, 0x1.179bep+6, 0x1.179d0ap+6, -0x4.9e34a8p-24, |
| 388 | 0x1.86e51cp-4, -0x2.cc7a68p-12, -0x3.3642c4p-8 }, /* 22 */ |
| 389 | { 0x1.242c5cp+6, 0x1.242ccap+6, 0x1.242d68p+6, 0x1.966706p-24, |
| 390 | -0x1.7e657p-4, 0x2.9aed4cp-12, 0x7.b87a58p-8 }, /* 23 */ |
| 391 | { 0x1.30bd62p+6, 0x1.30bdb6p+6, 0x1.30beb2p+6, 0x3.4b3b68p-24, |
| 392 | 0x1.766dc2p-4, -0x2.72651cp-12, -0x3.e347f8p-8 }, /* 24 */ |
| 393 | { 0x1.3d4e56p+6, 0x1.3d4ea2p+6, 0x1.3d4f2ep+6, 0x6.a99008p-28, |
| 394 | -0x1.6ef07ep-4, 0x2.53aec4p-12, 0x2.9e3d88p-12 }, /* 25 */ |
| 395 | { 0x1.49df38p+6, 0x1.49df9p+6, 0x1.49e042p+6, -0x7.a9fa6p-32, |
| 396 | 0x1.67e1dap-4, -0x2.324d7p-12, -0xc.0e669p-12 }, /* 26 */ |
| 397 | { 0x1.56702ep+6, 0x1.56708p+6, 0x1.567116p+6, -0x5.026808p-24, |
| 398 | -0x1.613798p-4, 0x2.114594p-12, 0x1.a22402p-8 }, /* 27 */ |
| 399 | { 0x1.630126p+6, 0x1.63017p+6, 0x1.630226p+6, 0x4.46aa2p-24, |
| 400 | 0x1.5ae8c2p-4, -0x1.f4aaa4p-12, -0x3.58593cp-8 }, /* 28 */ |
| 401 | { 0x1.6f9234p+6, 0x1.6f926p+6, 0x1.6f92b2p+6, 0x1.5cfccp-24, |
| 402 | -0x1.54ed76p-4, 0x1.dd540ap-12, -0xb.e9429p-12 }, /* 29 */ |
| 403 | { 0x1.7c22fep+6, 0x1.7c2352p+6, 0x1.7c23c2p+6, -0xb.4dc4cp-28, |
| 404 | 0x1.4f3ebcp-4, -0x1.c463fp-12, -0x1.e94c54p-8 }, /* 30 */ |
| 405 | { 0x1.88b412p+6, 0x1.88b444p+6, 0x1.88b50ap+6, 0x3.f5343p-24, |
| 406 | -0x1.49d668p-4, 0x1.a53f24p-12, 0x5.128198p-8 }, /* 31 */ |
| 407 | { 0x1.9544dcp+6, 0x1.954538p+6, 0x1.95459p+6, -0x6.e6f32p-28, |
| 408 | 0x1.44aefap-4, -0x1.9a6ef8p-12, -0x6.c639cp-8 }, /* 32 */ |
| 409 | { 0x1.a1d5fap+6, 0x1.a1d62cp+6, 0x1.a1d674p+6, 0x1.f359c2p-28, |
| 410 | -0x1.3fc386p-4, 0x1.887ebep-12, 0x1.6c813cp-8 }, /* 33 */ |
| 411 | { 0x1.ae66cp+6, 0x1.ae672p+6, 0x1.ae6788p+6, -0x2.9de748p-24, |
| 412 | 0x1.3b0fa4p-4, -0x1.777f26p-12, 0x1.c128ccp-8 }, /* 34 */ |
| 413 | { 0x1.baf7c2p+6, 0x1.baf816p+6, 0x1.baf86cp+6, -0x2.24ccc8p-24, |
| 414 | -0x1.368f5cp-4, 0x1.62bd9ep-12, 0xa.df002p-8 }, /* 35 */ |
| 415 | { 0x1.c788dap+6, 0x1.c7890cp+6, 0x1.c7896cp+6, 0x4.7dcea8p-24, |
| 416 | 0x1.323f16p-4, -0x1.61abf4p-12, 0xa.ad73ep-8 }, /* 36 */ |
| 417 | { 0x1.d419ccp+6, 0x1.d41a02p+6, 0x1.d41a68p+6, -0x4.b538p-24, |
| 418 | -0x1.2e1b98p-4, 0x1.4a4d64p-12, 0x3.a47674p-8 }, /* 37 */ |
| 419 | { 0x1.e0aacep+6, 0x1.e0aaf8p+6, 0x1.e0ab5ep+6, 0x3.09dc4cp-24, |
| 420 | 0x1.2a21ecp-4, -0x1.3fa20cp-12, 0x2.216e8cp-8 }, /* 38 */ |
| 421 | { 0x1.ed3bb8p+6, 0x1.ed3beep+6, 0x1.ed3c56p+6, 0x4.d5a58p-28, |
| 422 | -0x1.264f66p-4, 0x1.32c4cep-12, 0x1.53cbb4p-8 }, /* 39 */ |
| 423 | { 0x1.f9ccaep+6, 0x1.f9cce6p+6, 0x1.f9cd52p+6, 0x3.f4c44cp-24, |
| 424 | 0x1.22a192p-4, -0x1.1f8514p-12, -0xc.0de32p-8 }, /* 40 */ |
| 425 | { 0x1.032ed6p+7, 0x1.032eeep+7, 0x1.032f0cp+7, 0x2.4beae8p-24, |
| 426 | -0x1.1f1634p-4, 0x1.171664p-12, 0x1.72a654p-4 }, /* 41 */ |
| 427 | { 0x1.097756p+7, 0x1.09776ap+7, 0x1.09779cp+7, -0xd.a581ep-28, |
| 428 | 0x1.1bab3cp-4, -0xf.9f507p-16, -0xc.ba2d4p-8 }, /* 42 */ |
| 429 | { 0x1.0fbfdp+7, 0x1.0fbfe6p+7, 0x1.0fbff6p+7, 0xa.7c0bdp-28, |
| 430 | -0x1.185eccp-4, 0x1.01d7dep-12, -0x1.a2186ep-4 }, /* 43 */ |
| 431 | { 0x1.160856p+7, 0x1.160862p+7, 0x1.16087ap+7, -0x1.9452ecp-24, |
| 432 | 0x1.152f26p-4, -0x1.07b4aap-12, 0x1.6bbd7ep-4 }, /* 44 */ |
| 433 | { 0x1.1c50dp+7, 0x1.1c50dep+7, 0x1.1c5118p+7, 0x3.83b7b8p-24, |
| 434 | -0x1.121ab2p-4, 0x1.0e938cp-12, -0x5.1a6dfp-8 }, /* 45 */ |
| 435 | { 0x1.22995p+7, 0x1.22995ap+7, 0x1.229976p+7, -0x6.5ca3a8p-24, |
| 436 | 0x1.0f1ff2p-4, -0xe.f198p-16, -0x3.8e98b8p-8 }, /* 46 */ |
| 437 | { 0x1.28e1ccp+7, 0x1.28e1d8p+7, 0x1.28e1f4p+7, -0x6.bb61ap-24, |
| 438 | -0x1.0c3d8ap-4, 0xf.a14b9p-16, 0x9.81e82p-4 }, /* 47 */ |
| 439 | { 0x1.2f2a48p+7, 0x1.2f2a54p+7, 0x1.2f2a74p+7, 0x2.2438p-24, |
| 440 | 0x1.097236p-4, -0xd.fed5ep-16, -0x3.19eb5cp-8 }, /* 48 */ |
| 441 | { 0x1.3572b8p+7, 0x1.3572dp+7, 0x1.3572ecp+7, 0x3.1e0054p-24, |
| 442 | -0x1.06bcc8p-4, 0xd.d2596p-16, -0x1.67e00ap-4 }, /* 49 */ |
| 443 | { 0x1.3bbb3ep+7, 0x1.3bbb4ep+7, 0x1.3bbb6ap+7, 0x7.46c908p-24, |
| 444 | 0x1.041c28p-4, -0xd.04045p-16, -0x8.fb297p-8 }, /* 50 */ |
| 445 | { 0x1.4203aep+7, 0x1.4203cap+7, 0x1.4203e6p+7, -0xb.4f158p-28, |
| 446 | -0x1.018f52p-4, 0xc.ccf6fp-16, 0x1.4d5dp-4 }, /* 51 */ |
| 447 | { 0x1.484c38p+7, 0x1.484c46p+7, 0x1.484c56p+7, -0x6.5a89c8p-24, |
| 448 | 0xf.f155p-8, -0xc.5d21dp-16, -0xd.aca34p-8 }, /* 52 */ |
| 449 | { 0x1.4e94b8p+7, 0x1.4e94c4p+7, 0x1.4e94d4p+7, -0x1.ef16c8p-24, |
| 450 | -0xf.cad3fp-8, 0xb.d75f8p-16, 0x1.f36732p-4 }, /* 53 */ |
| 451 | { 0x1.54dd36p+7, 0x1.54dd4p+7, 0x1.54dd52p+7, -0x6.1e7b68p-24, |
| 452 | 0xf.a564cp-8, -0xb.ec1cfp-16, 0xe.e7421p-8 }, /* 54 */ |
| 453 | { 0x1.5b25aep+7, 0x1.5b25bep+7, 0x1.5b25d4p+7, -0xf.8c858p-28, |
| 454 | -0xf.80faep-8, 0xb.8b6c5p-16, -0x5.835ed8p-8 }, /* 55 */ |
| 455 | { 0x1.616e34p+7, 0x1.616e3cp+7, 0x1.616e4ep+7, 0x7.75d858p-24, |
| 456 | 0xf.5d8abp-8, -0xb.b3779p-16, 0x2.40b948p-4 }, /* 56 */ |
| 457 | { 0x1.67b6bp+7, 0x1.67b6b8p+7, 0x1.67b6dp+7, 0x1.d78632p-24, |
| 458 | -0xf.3b096p-8, 0xa.daf89p-16, 0x1.aa8548p-8 }, /* 57 */ |
| 459 | { 0x1.6dff28p+7, 0x1.6dff36p+7, 0x1.6dff54p+7, 0x3.b24794p-24, |
| 460 | 0xf.196c7p-8, -0xb.1afe1p-16, -0x1.77538cp-8 }, /* 58 */ |
| 461 | { 0x1.7447a2p+7, 0x1.7447b2p+7, 0x1.7447cap+7, 0x6.39cbc8p-24, |
| 462 | -0xe.f8aa5p-8, 0xa.50daap-16, 0x1.9592c2p-8 }, /* 59 */ |
| 463 | { 0x1.7a902p+7, 0x1.7a903p+7, 0x1.7a903ep+7, -0x1.820e3ap-24, |
| 464 | 0xe.d8b9dp-8, -0xa.998cp-16, -0x2.c35d78p-4 }, /* 60 */ |
| 465 | { 0x1.80d89ep+7, 0x1.80d8aep+7, 0x1.80d8bep+7, -0x2.c7e038p-24, |
| 466 | -0xe.b9925p-8, 0x9.ce06p-16, -0x2.2b3054p-4 }, /* 61 */ |
| 467 | { 0x1.87211cp+7, 0x1.87212cp+7, 0x1.872144p+7, 0x6.ab31c8p-24, |
| 468 | 0xe.9b2bep-8, -0x9.4de7p-16, -0x1.32cb5ep-4 }, /* 62 */ |
| 469 | { 0x1.8d699ap+7, 0x1.8d69a8p+7, 0x1.8d69bp+7, 0x4.4ef25p-24, |
| 470 | -0xe.7d7ecp-8, 0x9.a0f1ep-16, 0x1.6ac076p-4 }, /* 63 */ |
| 471 | }; |
| 472 | |
| 473 | /* Formula page 5 of https://www.cl.cam.ac.uk/~jrh13/papers/bessel.pdf: |
| 474 | y0(x) ~ sqrt(2/(pi*x))*beta0(x)*sin(x-pi/4-alpha0(x)) |
| 475 | where beta0(x) = 1 - 1/(16*x^2) + 53/(512*x^4) |
| 476 | and alpha0(x) = 1/(8*x) - 25/(384*x^3). */ |
| 477 | static float |
| 478 | y0f_asympt (float x) |
| 479 | { |
| 480 | /* The following code fails to give an error <= 9 ulps in only two cases, |
| 481 | for which we tabulate the correctly-rounded result. */ |
| 482 | if (x == 0x1.bfad96p+7f) |
| 483 | return -0x7.f32bdp-32f; |
| 484 | if (x == 0x1.2e2a42p+17f) |
| 485 | return 0x1.a48974p-40f; |
| 486 | double y = 1.0 / (double) x; |
| 487 | double y2 = y * y; |
| 488 | double beta0 = 1.0f + y2 * (-0x1p-4f + 0x1.a8p-4 * y2); |
| 489 | double alpha0 = y * (0x2p-4 - 0x1.0aaaaap-4 * y2); |
| 490 | double h; |
| 491 | int n; |
| 492 | h = reduce_aux (x, &n, alpha0); |
| 493 | /* Now x - pi/4 - alpha0 = h + n*pi/2 mod (2*pi). */ |
| 494 | float xr = (float) h; |
| 495 | n = n & 3; |
| 496 | float cst = 0xc.c422ap-4; /* sqrt(2/pi) rounded to nearest */ |
| 497 | float t = cst / sqrtf (x) * (float) beta0; |
| 498 | if (n == 0) |
| 499 | return t * __sinf (xr); |
| 500 | else if (n == 2) /* sin(x+pi) = -sin(x) */ |
| 501 | return -t * __sinf (xr); |
| 502 | else if (n == 1) /* sin(x+pi/2) = cos(x) */ |
| 503 | return t * __cosf (xr); |
| 504 | else /* sin(x+3pi/2) = -cos(x) */ |
| 505 | return -t * __cosf (xr); |
| 506 | } |
| 507 | |
| 508 | /* Special code for x near a root of y0. |
| 509 | z is the value computed by the generic code. |
| 510 | For small x, use a polynomial approximating y0 around its root. |
| 511 | For large x, use an asymptotic formula (y0f_asympt). */ |
| 512 | static float |
| 513 | y0f_near_root (float x, float z) |
| 514 | { |
| 515 | float index_f; |
| 516 | int index; |
| 517 | |
| 518 | index_f = roundf ((x - FIRST_ZERO_Y0) / (float) M_PI); |
| 519 | if (index_f >= SMALL_SIZE) |
| 520 | return y0f_asympt (x); |
| 521 | index = (int) index_f; |
| 522 | const float *p = Py[index]; |
| 523 | float x0 = p[0]; |
| 524 | float x1 = p[2]; |
| 525 | /* If not in the interval [x0,x1] around xmid, return the value z. */ |
| 526 | if (! (x0 <= x && x <= x1)) |
| 527 | return z; |
| 528 | float xmid = p[1]; |
| 529 | float y = x - xmid; |
| 530 | /* For degree 0 use a degree-5 polynomial, where the coefficients of |
| 531 | degree 4 and 5 are hard-coded. */ |
| 532 | float p6 = (index > 0) ? p[6] |
| 533 | : p[6] + y * (-0x3.a46c9p-4 + y * 0x3.735478p-4); |
| 534 | float res = p[3] + y * (p[4] + y * (p[5] + y * p6)); |
| 535 | return res; |
| 536 | } |
| 537 | |
| 538 | float |
| 539 | __ieee754_y0f(float x) |
| 540 | { |
| 541 | float z, s,c,ss,cc,u,v; |
| 542 | int32_t hx,ix; |
| 543 | |
| 544 | GET_FLOAT_WORD(hx,x); |
| 545 | ix = 0x7fffffff&hx; |
| 546 | /* Y0(NaN) is NaN, y0(-inf) is Nan, y0(inf) is 0, y0(0) is -inf. */ |
| 547 | if(ix>=0x7f800000) return one/(x+x*x); |
| 548 | if(ix==0) return -1/zero; /* -inf and divide by zero exception. */ |
| 549 | if(hx<0) return zero/(zero*x); |
| 550 | if(ix >= 0x40000000 || (0x3f5340ed <= ix && ix <= 0x3f77b5e5)) { |
| 551 | /* |x| >= 2.0 or |
| 552 | 0x1.a681dap-1 <= |x| <= 0x1.ef6bcap-1 (around 1st zero) */ |
| 553 | /* y0(x) = sqrt(2/(pi*x))*(p0(x)*sin(x0)+q0(x)*cos(x0)) |
| 554 | * where x0 = x-pi/4 |
| 555 | * Better formula: |
| 556 | * cos(x0) = cos(x)cos(pi/4)+sin(x)sin(pi/4) |
| 557 | * = 1/sqrt(2) * (sin(x) + cos(x)) |
| 558 | * sin(x0) = sin(x)cos(3pi/4)-cos(x)sin(3pi/4) |
| 559 | * = 1/sqrt(2) * (sin(x) - cos(x)) |
| 560 | * To avoid cancellation, use |
| 561 | * sin(x) +- cos(x) = -cos(2x)/(sin(x) -+ cos(x)) |
| 562 | * to compute the worse one. |
| 563 | */ |
| 564 | SET_RESTORE_ROUNDF (FE_TONEAREST); |
| 565 | __sincosf (x, &s, &c); |
| 566 | ss = s-c; |
| 567 | cc = s+c; |
| 568 | /* |
| 569 | * j0(x) = 1/sqrt(pi) * (P(0,x)*cc - Q(0,x)*ss) / sqrt(x) |
| 570 | * y0(x) = 1/sqrt(pi) * (P(0,x)*ss + Q(0,x)*cc) / sqrt(x) |
| 571 | */ |
| 572 | if (ix >= 0x7f000000) |
| 573 | /* x >= 2^127: use asymptotic expansion. */ |
| 574 | return y0f_asympt (x); |
| 575 | /* Now we are sure that x+x cannot overflow. */ |
| 576 | z = -__cosf(x+x); |
| 577 | if ((s*c)<zero) cc = z/ss; |
| 578 | else ss = z/cc; |
| 579 | if (ix <= 0x5c000000) |
| 580 | { |
| 581 | u = pzerof(x); v = qzerof(x); |
| 582 | ss = u*ss+v*cc; |
| 583 | } |
| 584 | z = (invsqrtpi*ss)/sqrtf(x); |
| 585 | /* The following threshold is optimal (determined on |
| 586 | aarch64-linux-gnu). */ |
| 587 | float threshold = 0x1.be585ap-4; |
| 588 | if (fabsf (ss) > threshold) |
| 589 | return z; |
| 590 | else |
| 591 | return y0f_near_root (x, z); |
| 592 | } |
| 593 | if(ix<=0x39800000) { /* x < 2**-13 */ |
| 594 | return(u00 + tpi*__ieee754_logf(x)); |
| 595 | } |
| 596 | z = x*x; |
| 597 | u = u00+z*(u01+z*(u02+z*(u03+z*(u04+z*(u05+z*u06))))); |
| 598 | v = one+z*(v01+z*(v02+z*(v03+z*v04))); |
| 599 | return(u/v + tpi*(__ieee754_j0f(x)*__ieee754_logf(x))); |
| 600 | } |
| 601 | libm_alias_finite (__ieee754_y0f, __y0f) |
| 602 | |
| 603 | /* The asymptotic expansion of pzero is |
| 604 | * 1 - 9/128 s^2 + 11025/98304 s^4 - ..., where s = 1/x. |
| 605 | * For x >= 2, We approximate pzero by |
| 606 | * pzero(x) = 1 + (R/S) |
| 607 | * where R = pR0 + pR1*s^2 + pR2*s^4 + ... + pR5*s^10 |
| 608 | * S = 1 + pS0*s^2 + ... + pS4*s^10 |
| 609 | * and |
| 610 | * | pzero(x)-1-R/S | <= 2 ** ( -60.26) |
| 611 | */ |
| 612 | static const float pR8[6] = { /* for x in [inf, 8]=1/[0,0.125] */ |
| 613 | 0.0000000000e+00, /* 0x00000000 */ |
| 614 | -7.0312500000e-02, /* 0xbd900000 */ |
| 615 | -8.0816707611e+00, /* 0xc1014e86 */ |
| 616 | -2.5706311035e+02, /* 0xc3808814 */ |
| 617 | -2.4852163086e+03, /* 0xc51b5376 */ |
| 618 | -5.2530439453e+03, /* 0xc5a4285a */ |
| 619 | }; |
| 620 | static const float pS8[5] = { |
| 621 | 1.1653436279e+02, /* 0x42e91198 */ |
| 622 | 3.8337448730e+03, /* 0x456f9beb */ |
| 623 | 4.0597855469e+04, /* 0x471e95db */ |
| 624 | 1.1675296875e+05, /* 0x47e4087c */ |
| 625 | 4.7627726562e+04, /* 0x473a0bba */ |
| 626 | }; |
| 627 | static const float pR5[6] = { /* for x in [8,4.5454]=1/[0.125,0.22001] */ |
| 628 | -1.1412546255e-11, /* 0xad48c58a */ |
| 629 | -7.0312492549e-02, /* 0xbd8fffff */ |
| 630 | -4.1596107483e+00, /* 0xc0851b88 */ |
| 631 | -6.7674766541e+01, /* 0xc287597b */ |
| 632 | -3.3123129272e+02, /* 0xc3a59d9b */ |
| 633 | -3.4643338013e+02, /* 0xc3ad3779 */ |
| 634 | }; |
| 635 | static const float pS5[5] = { |
| 636 | 6.0753936768e+01, /* 0x42730408 */ |
| 637 | 1.0512523193e+03, /* 0x44836813 */ |
| 638 | 5.9789707031e+03, /* 0x45bad7c4 */ |
| 639 | 9.6254453125e+03, /* 0x461665c8 */ |
| 640 | 2.4060581055e+03, /* 0x451660ee */ |
| 641 | }; |
| 642 | |
| 643 | static const float pR3[6] = {/* for x in [4.547,2.8571]=1/[0.2199,0.35001] */ |
| 644 | -2.5470459075e-09, /* 0xb12f081b */ |
| 645 | -7.0311963558e-02, /* 0xbd8fffb8 */ |
| 646 | -2.4090321064e+00, /* 0xc01a2d95 */ |
| 647 | -2.1965976715e+01, /* 0xc1afba52 */ |
| 648 | -5.8079170227e+01, /* 0xc2685112 */ |
| 649 | -3.1447946548e+01, /* 0xc1fb9565 */ |
| 650 | }; |
| 651 | static const float pS3[5] = { |
| 652 | 3.5856033325e+01, /* 0x420f6c94 */ |
| 653 | 3.6151397705e+02, /* 0x43b4c1ca */ |
| 654 | 1.1936077881e+03, /* 0x44953373 */ |
| 655 | 1.1279968262e+03, /* 0x448cffe6 */ |
| 656 | 1.7358093262e+02, /* 0x432d94b8 */ |
| 657 | }; |
| 658 | |
| 659 | static const float pR2[6] = {/* for x in [2.8570,2]=1/[0.3499,0.5] */ |
| 660 | -8.8753431271e-08, /* 0xb3be98b7 */ |
| 661 | -7.0303097367e-02, /* 0xbd8ffb12 */ |
| 662 | -1.4507384300e+00, /* 0xbfb9b1cc */ |
| 663 | -7.6356959343e+00, /* 0xc0f4579f */ |
| 664 | -1.1193166733e+01, /* 0xc1331736 */ |
| 665 | -3.2336456776e+00, /* 0xc04ef40d */ |
| 666 | }; |
| 667 | static const float pS2[5] = { |
| 668 | 2.2220300674e+01, /* 0x41b1c32d */ |
| 669 | 1.3620678711e+02, /* 0x430834f0 */ |
| 670 | 2.7047027588e+02, /* 0x43873c32 */ |
| 671 | 1.5387539673e+02, /* 0x4319e01a */ |
| 672 | 1.4657617569e+01, /* 0x416a859a */ |
| 673 | }; |
| 674 | |
| 675 | static float |
| 676 | pzerof(float x) |
| 677 | { |
| 678 | const float *p,*q; |
| 679 | float z,r,s; |
| 680 | int32_t ix; |
| 681 | GET_FLOAT_WORD(ix,x); |
| 682 | ix &= 0x7fffffff; |
| 683 | /* ix >= 0x40000000 for all calls to this function. */ |
| 684 | if(ix>=0x41000000) {p = pR8; q= pS8;} |
| 685 | else if(ix>=0x40f71c58){p = pR5; q= pS5;} |
| 686 | else if(ix>=0x4036db68){p = pR3; q= pS3;} |
| 687 | else {p = pR2; q= pS2;} |
| 688 | z = one/(x*x); |
| 689 | r = p[0]+z*(p[1]+z*(p[2]+z*(p[3]+z*(p[4]+z*p[5])))); |
| 690 | s = one+z*(q[0]+z*(q[1]+z*(q[2]+z*(q[3]+z*q[4])))); |
| 691 | return one+ r/s; |
| 692 | } |
| 693 | |
| 694 | |
| 695 | /* For x >= 8, the asymptotic expansion of qzero is |
| 696 | * -1/8 s + 75/1024 s^3 - ..., where s = 1/x. |
| 697 | * We approximate pzero by |
| 698 | * qzero(x) = s*(-1.25 + (R/S)) |
| 699 | * where R = qR0 + qR1*s^2 + qR2*s^4 + ... + qR5*s^10 |
| 700 | * S = 1 + qS0*s^2 + ... + qS5*s^12 |
| 701 | * and |
| 702 | * | qzero(x)/s +1.25-R/S | <= 2 ** ( -61.22) |
| 703 | */ |
| 704 | static const float qR8[6] = { /* for x in [inf, 8]=1/[0,0.125] */ |
| 705 | 0.0000000000e+00, /* 0x00000000 */ |
| 706 | 7.3242187500e-02, /* 0x3d960000 */ |
| 707 | 1.1768206596e+01, /* 0x413c4a93 */ |
| 708 | 5.5767340088e+02, /* 0x440b6b19 */ |
| 709 | 8.8591972656e+03, /* 0x460a6cca */ |
| 710 | 3.7014625000e+04, /* 0x471096a0 */ |
| 711 | }; |
| 712 | static const float qS8[6] = { |
| 713 | 1.6377603149e+02, /* 0x4323c6aa */ |
| 714 | 8.0983447266e+03, /* 0x45fd12c2 */ |
| 715 | 1.4253829688e+05, /* 0x480b3293 */ |
| 716 | 8.0330925000e+05, /* 0x49441ed4 */ |
| 717 | 8.4050156250e+05, /* 0x494d3359 */ |
| 718 | -3.4389928125e+05, /* 0xc8a7eb69 */ |
| 719 | }; |
| 720 | |
| 721 | static const float qR5[6] = { /* for x in [8,4.5454]=1/[0.125,0.22001] */ |
| 722 | 1.8408595828e-11, /* 0x2da1ec79 */ |
| 723 | 7.3242180049e-02, /* 0x3d95ffff */ |
| 724 | 5.8356351852e+00, /* 0x40babd86 */ |
| 725 | 1.3511157227e+02, /* 0x43071c90 */ |
| 726 | 1.0272437744e+03, /* 0x448067cd */ |
| 727 | 1.9899779053e+03, /* 0x44f8bf4b */ |
| 728 | }; |
| 729 | static const float qS5[6] = { |
| 730 | 8.2776611328e+01, /* 0x42a58da0 */ |
| 731 | 2.0778142090e+03, /* 0x4501dd07 */ |
| 732 | 1.8847289062e+04, /* 0x46933e94 */ |
| 733 | 5.6751113281e+04, /* 0x475daf1d */ |
| 734 | 3.5976753906e+04, /* 0x470c88c1 */ |
| 735 | -5.3543427734e+03, /* 0xc5a752be */ |
| 736 | }; |
| 737 | |
| 738 | static const float qR3[6] = {/* for x in [4.547,2.8571]=1/[0.2199,0.35001] */ |
| 739 | 4.3774099900e-09, /* 0x3196681b */ |
| 740 | 7.3241114616e-02, /* 0x3d95ff70 */ |
| 741 | 3.3442313671e+00, /* 0x405607e3 */ |
| 742 | 4.2621845245e+01, /* 0x422a7cc5 */ |
| 743 | 1.7080809021e+02, /* 0x432acedf */ |
| 744 | 1.6673394775e+02, /* 0x4326bbe4 */ |
| 745 | }; |
| 746 | static const float qS3[6] = { |
| 747 | 4.8758872986e+01, /* 0x42430916 */ |
| 748 | 7.0968920898e+02, /* 0x44316c1c */ |
| 749 | 3.7041481934e+03, /* 0x4567825f */ |
| 750 | 6.4604252930e+03, /* 0x45c9e367 */ |
| 751 | 2.5163337402e+03, /* 0x451d4557 */ |
| 752 | -1.4924745178e+02, /* 0xc3153f59 */ |
| 753 | }; |
| 754 | |
| 755 | static const float qR2[6] = {/* for x in [2.8570,2]=1/[0.3499,0.5] */ |
| 756 | 1.5044444979e-07, /* 0x342189db */ |
| 757 | 7.3223426938e-02, /* 0x3d95f62a */ |
| 758 | 1.9981917143e+00, /* 0x3fffc4bf */ |
| 759 | 1.4495602608e+01, /* 0x4167edfd */ |
| 760 | 3.1666231155e+01, /* 0x41fd5471 */ |
| 761 | 1.6252708435e+01, /* 0x4182058c */ |
| 762 | }; |
| 763 | static const float qS2[6] = { |
| 764 | 3.0365585327e+01, /* 0x41f2ecb8 */ |
| 765 | 2.6934811401e+02, /* 0x4386ac8f */ |
| 766 | 8.4478375244e+02, /* 0x44533229 */ |
| 767 | 8.8293585205e+02, /* 0x445cbbe5 */ |
| 768 | 2.1266638184e+02, /* 0x4354aa98 */ |
| 769 | -5.3109550476e+00, /* 0xc0a9f358 */ |
| 770 | }; |
| 771 | |
| 772 | static float |
| 773 | qzerof(float x) |
| 774 | { |
| 775 | const float *p,*q; |
| 776 | float s,r,z; |
| 777 | int32_t ix; |
| 778 | GET_FLOAT_WORD(ix,x); |
| 779 | ix &= 0x7fffffff; |
| 780 | /* ix >= 0x40000000 for all calls to this function. */ |
| 781 | if(ix>=0x41000000) {p = qR8; q= qS8;} |
| 782 | else if(ix>=0x40f71c58){p = qR5; q= qS5;} |
| 783 | else if(ix>=0x4036db68){p = qR3; q= qS3;} |
| 784 | else {p = qR2; q= qS2;} |
| 785 | z = one/(x*x); |
| 786 | r = p[0]+z*(p[1]+z*(p[2]+z*(p[3]+z*(p[4]+z*p[5])))); |
| 787 | s = one+z*(q[0]+z*(q[1]+z*(q[2]+z*(q[3]+z*(q[4]+z*q[5]))))); |
| 788 | return (-(float).125 + r/s)/x; |
| 789 | } |
| 790 |
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