Coverage for pygeodesy / fmath.py: 89%

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1 

2# -*- coding: utf-8 -*- 

3 

4u'''Utilities for precision floating point summation, multiplication, 

5C{fused-multiply-add}, polynomials, roots, etc. 

6''' 

7# make sure int/int division yields float quotient, see .basics 

8from __future__ import division as _; del _ # noqa: E702 ; 

9 

10from pygeodesy.basics import _copysign, copysign0, isbool, isint, isodd, \ 

11 isscalar, len2, _xiterable, _zip, typename 

12from pygeodesy.constants import EPS0, EPS02, EPS1, NAN, PI, PI_2, PI_4, \ 

13 _0_0, _0_125, _0_25, _1_3rd, _0_5, _2_3rd, \ 

14 _1_0, _1_5, _copysign_0_0, isfinite, remainder 

15from pygeodesy.errors import _IsnotError, LenError, _TypeError, _ValueError, \ 

16 _xError, _xkwds, _xkwds_get, _xkwds_pop2, _xsError 

17from pygeodesy.fsums import _2float, Fsum, fsum, _isFsum_2Tuple 

18# from pygeodesy.internals import typename # from .basics 

19from pygeodesy.interns import MISSING, _negative_, _not_scalar_ 

20from pygeodesy.lazily import _ALL_LAZY, _ALL_MODS as _MODS 

21from pygeodesy.streprs import Fmt, unstr 

22from pygeodesy.units import Int_, _isHeight, _isRadius 

23# from utily import atan2b, atan2p # _MODS, circular import! 

24 

25from math import fabs, sqrt # pow 

26import operator as _operator # in .datums, .elliptic, .trf, .utm 

27 

28__all__ = _ALL_LAZY.fmath 

29__version__ = '26.10.04' 

30 

31# 1.4142135623730950_48801688724209 <https://WikiPedia.org/wiki/Square_root_of_2> 

32# math.sqrt(2) - 1 == 0.4142135623730950_3 == 3730904090310553 / 9007199254740992 

33_0_4142 = 0.4142135623730950488 

34_1_6th = 1 / 6 

35_h_lt_b_ = 'abs(h) < abs(b)' 

36 

37 

38class Fdot(Fsum): 

39 '''Precision dot product. 

40 ''' 

41 def __init__(self, a, *b, **start_name_f2product_nonfinites_RESIDUAL): 

42 '''New L{Fdot} precision dot product M{start + sum(a[i] * b[i] for i=0..len(a)-1)}. 

43 

44 @arg a: Iterable of values (each C{scalar}, an L{Fsum} or L{Fsum2Tuple}). 

45 @arg b: Other values (each C{scalar}, an L{Fsum} or L{Fsum2Tuple}), all 

46 positional. 

47 @kwarg start_name_f2product_nonfinites_RESIDUAL: Optional bias C{B{start}=0} 

48 (C{scalar}, an L{Fsum} or L{Fsum2Tuple}), C{B{name}=NN} (C{str}) 

49 and other settings, see class L{Fsum<Fsum.__init__>}. 

50 

51 @raise LenError: Unequal C{len(B{a})} and C{len(B{b})}. 

52 

53 @raise OverflowError: Partial C{2sum} overflow. 

54 

55 @raise TypeError: Invalid B{C{x}}. 

56 

57 @raise ValueError: Non-finite B{C{x}}. 

58 

59 @see: Function L{fdot} and method L{Fsum.fadd}. 

60 ''' 

61 s, kwds = _xkwds_pop2(start_name_f2product_nonfinites_RESIDUAL, start=_0_0) 

62 Fsum.__init__(self, **kwds) 

63 self(s) 

64 

65 n = len(b) 

66 if len(a) != n: # PYCHOK no cover 

67 raise LenError(Fdot, a=len(a), b=n) 

68 self._facc_dot(n, a, b, **kwds) 

69 

70 

71class Fdot_(Fdot): # in .elliptic 

72 '''Precision dot product. 

73 ''' 

74 def __init__(self, *xys, **start_name_f2product_nonfinites_RESIDUAL): 

75 '''New L{Fdot_} precision dot product M{start + sum(xys[i] * xys[i+1] for i in 

76 range(0, len(xys), B{2}))}. 

77 

78 @arg xys: Pairwise values (each C{scalar}, an L{Fsum} or L{Fsum2Tuple}), 

79 all positional. 

80 

81 @see: Class L{Fdot<Fdot.__init__>} for further details. 

82 ''' 

83 if isodd(len(xys)): 

84 raise LenError(Fdot_, xys=len(xys)) 

85 Fdot.__init__(self, xys[0::2], *xys[1::2], **start_name_f2product_nonfinites_RESIDUAL) 

86 

87 

88class Fhorner(Fsum): 

89 '''Precision polynomial evaluation using the Horner form. 

90 ''' 

91 def __init__(self, x, *cs, **incx_name_f2product_nonfinites_RESIDUAL): 

92 '''New L{Fhorner} form evaluation of polynomial M{sum(cs[i] * x**i for i=0..n)} 

93 with in- or decreasing exponent M{sum(... i=n..0)}, where C{n = len(cs) - 1}. 

94 

95 @arg x: Polynomial argument (C{scalar}, an L{Fsum} or L{Fsum2Tuple}). 

96 @arg cs: Polynomial coeffients (each C{scalar}, an L{Fsum} or L{Fsum2Tuple}), 

97 all positional. 

98 @kwarg incx_name_f2product_nonfinites_RESIDUAL: Optional C{B{name}=NN} (C{str}), 

99 C{B{incx}=True} for in-/decreasing exponents (C{bool}) and other 

100 settings, see class L{Fsum<Fsum.__init__>}. 

101 

102 @raise OverflowError: Partial C{2sum} overflow. 

103 

104 @raise TypeError: Invalid B{C{x}}. 

105 

106 @raise ValueError: Non-finite B{C{x}}. 

107 

108 @see: Function L{fhorner} and methods L{Fsum.fadd} and L{Fsum.fmul}. 

109 ''' 

110 incx, kwds = _xkwds_pop2(incx_name_f2product_nonfinites_RESIDUAL, incx=True) 

111 Fsum.__init__(self, **kwds) 

112 self._fhorner(x, cs, Fhorner, incx=incx) 

113 

114 

115class Fhypot(Fsum): 

116 '''Precision summation and hypotenuse, default C{root=2}. 

117 ''' 

118 def __init__(self, *xs, **root_name_f2product_nonfinites_RESIDUAL_raiser): 

119 '''New L{Fhypot} hypotenuse of (the I{root} of) several components (raised 

120 to the power I{root}). 

121 

122 @arg xs: Components (each C{scalar}, an L{Fsum} or L{Fsum2Tuple}), all 

123 positional. 

124 @kwarg root_name_f2product_nonfinites_RESIDUAL_raiser: Optional, exponent 

125 and C{B{root}=2} order (C{scalar}), C{B{name}=NN} (C{str}), 

126 C{B{raiser}=True} (C{bool}) for raising L{ResidualError}s and 

127 other settings, see class L{Fsum<Fsum.__init__>} and method 

128 L{root<Fsum.root>}. 

129 ''' 

130 def _r_X_kwds(power=None, raiser=True, root=2, **kwds): 

131 # DEPRECATED keyword argument C{power=2}, use C{root=2} 

132 return (root if power is None else power), raiser, kwds 

133 

134 r = None # _xkwds_pop2 error 

135 try: 

136 r, X, kwds = _r_X_kwds(**root_name_f2product_nonfinites_RESIDUAL_raiser) 

137 Fsum.__init__(self, **kwds) 

138 self(_0_0) 

139 if xs: 

140 self._facc_power(r, xs, Fhypot, raiser=X) 

141 self._fset(self.root(r, raiser=X)) 

142 except Exception as X: 

143 raise self._ErrorXs(X, xs, root=r) 

144 

145 

146class Fpolynomial(Fsum): 

147 '''Precision polynomial evaluation. 

148 ''' 

149 def __init__(self, x, *cs, **name_f2product_nonfinites_RESIDUAL): 

150 '''New L{Fpolynomial} evaluation of the polynomial M{sum(cs[i] * x**i for 

151 i=0..len(cs)-1)}. 

152 

153 @arg x: Polynomial argument (C{scalar}, an L{Fsum} or L{Fsum2Tuple}). 

154 @arg cs: Polynomial coeffients (each C{scalar}, an L{Fsum} or L{Fsum2Tuple}), 

155 all positional. 

156 @kwarg name_f2product_nonfinites_RESIDUAL: Optional C{B{name}=NN} (C{str}) 

157 and other settings, see class L{Fsum<Fsum.__init__>}. 

158 

159 @raise OverflowError: Partial C{2sum} overflow. 

160 

161 @raise TypeError: Invalid B{C{x}}. 

162 

163 @raise ValueError: Non-finite B{C{x}}. 

164 

165 @see: Class L{Fhorner}, function L{fpolynomial} and method L{Fsum.fadd}. 

166 ''' 

167 Fsum.__init__(self, **name_f2product_nonfinites_RESIDUAL) 

168 n = len(cs) - 1 

169 self(_0_0 if n < 0 else cs[0]) 

170 self._facc_dot(n, cs[1:], _powers(x, n), **name_f2product_nonfinites_RESIDUAL) 

171 

172 

173class Fpowers(Fsum): 

174 '''Precision summation of powers, optimized for C{power=2, 3 and 4}. 

175 ''' 

176 def __init__(self, power, *xs, **name_f2product_nonfinites_RESIDUAL_raiser): 

177 '''New L{Fpowers} sum of (the I{power} of) several bases. 

178 

179 @arg power: The exponent (C{scalar}, an L{Fsum} or L{Fsum2Tuple}). 

180 @arg xs: One or more bases (each C{scalar}, an L{Fsum} or L{Fsum2Tuple}), all 

181 positional. 

182 @kwarg name_f2product_nonfinites_RESIDUAL_raiser: Optional C{B{name}=NN} 

183 (C{str}), C{B{raiser}=True} (C{bool}) for raising L{ResidualError}s 

184 and other settings, see class L{Fsum<Fsum.__init__>} and method 

185 L{fpow<Fsum.fpow>}. 

186 ''' 

187 try: 

188 X, kwds = _xkwds_pop2(name_f2product_nonfinites_RESIDUAL_raiser, raiser=True) 

189 Fsum.__init__(self, **kwds) 

190 self(_0_0) 

191 if xs: 

192 self._facc_power(power, xs, Fpowers, raiser=X) # x**0 == 1 

193 except Exception as X: 

194 raise self._ErrorXs(X, xs, power=power) 

195 

196 

197class Froot(Fsum): 

198 '''The root of a precision summation. 

199 ''' 

200 def __init__(self, root, *xs, **name_f2product_nonfinites_RESIDUAL_raiser): 

201 '''New L{Froot} root of a precision sum. 

202 

203 @arg root: The order (C{scalar}, an L{Fsum} or L{Fsum2Tuple}), non-zero. 

204 @arg xs: Items to summate (each a C{scalar}, an L{Fsum} or L{Fsum2Tuple}), all 

205 positional. 

206 @kwarg name_f2product_nonfinites_RESIDUAL_raiser: Optional C{B{name}=NN} 

207 (C{str}), C{B{raiser}=True} (C{bool}) for raising L{ResidualError}s 

208 and other settings, see class L{Fsum<Fsum.__init__>} and method 

209 L{fpow<Fsum.fpow>}. 

210 ''' 

211 try: 

212 X, kwds = _xkwds_pop2(name_f2product_nonfinites_RESIDUAL_raiser, raiser=True) 

213 Fsum.__init__(self, **kwds) 

214 self(_0_0) 

215 if xs: 

216 self.fadd(xs) 

217 self(self.root(root, raiser=X)) 

218 except Exception as X: 

219 raise self._ErrorXs(X, xs, root=root) 

220 

221 

222class Fcbrt(Froot): 

223 '''Cubic root of a precision summation. 

224 ''' 

225 def __init__(self, *xs, **name_f2product_nonfinites_RESIDUAL_raiser): 

226 '''New L{Fcbrt} cubic root of a precision sum. 

227 

228 @see: Class L{Froot<Froot.__init__>} for further details. 

229 ''' 

230 Froot.__init__(self, 3, *xs, **name_f2product_nonfinites_RESIDUAL_raiser) 

231 

232 

233class Fsqrt(Froot): 

234 '''Square root of a precision summation. 

235 ''' 

236 def __init__(self, *xs, **name_f2product_nonfinites_RESIDUAL_raiser): 

237 '''New L{Fsqrt} square root of a precision sum. 

238 

239 @see: Class L{Froot<Froot.__init__>} for further details. 

240 ''' 

241 Froot.__init__(self, 2, *xs, **name_f2product_nonfinites_RESIDUAL_raiser) 

242 

243 

244def bqrt(x): 

245 '''Return the 4-th, I{bi-quadratic} or I{quartic} root, M{x**(1 / 4)}, 

246 preserving C{type(B{x})}. 

247 

248 @arg x: Value (C{scalar}, an L{Fsum} or L{Fsum2Tuple}). 

249 

250 @return: I{Quartic} root (C{float} or an L{Fsum}). 

251 

252 @raise TypeeError: Invalid B{C{x}}. 

253 

254 @raise ValueError: Negative B{C{x}}. 

255 

256 @see: Functions L{zcrt} and L{zqrt}. 

257 ''' 

258 return _root(x, _0_25, bqrt) 

259 

260 

261try: 

262 from math import cbrt as _cbrt # Python 3.11+ 

263except ImportError: # Python 3.10- 

264 

265 def _cbrt(x): 

266 '''(INTERNAL) Compute the I{signed}, cube root M{x**(1/3)}. 

267 ''' 

268 # <https://archive.lib.MSU.edu/crcmath/math/math/r/r021.htm> 

269 # simpler and more accurate than Ken Turkowski's CubeRoot, see 

270 # <https://People.FreeBSD.org/~lstewart/references/apple_tr_kt32_cuberoot.pdf> 

271 return _copysign(pow(fabs(x), _1_3rd), x) # to avoid complex 

272 

273 

274def cbrt(x): 

275 '''Compute the cube root M{x**(1/3)}, preserving C{type(B{x})}. 

276 

277 @arg x: Value (C{scalar}, an L{Fsum} or L{Fsum2Tuple}). 

278 

279 @return: Cubic root (C{float} or L{Fsum}). 

280 

281 @see: Functions L{cbrt2} and L{sqrt3}. 

282 ''' 

283 if _isFsum_2Tuple(x): 

284 r = abs(x).fpow(_1_3rd) 

285 if x.signOf() < 0: 

286 r = -r 

287 else: 

288 r = _cbrt(x) 

289 return r # cbrt(-0.0) == -0.0 

290 

291 

292def cbrt2(x): # PYCHOK attr 

293 '''Compute the cube root I{squared} M{x**(2/3)}, preserving C{type(B{x})}. 

294 

295 @arg x: Value (C{scalar}, an L{Fsum} or L{Fsum2Tuple}). 

296 

297 @return: Cube root I{squared} (C{float} or L{Fsum}). 

298 

299 @see: Functions L{cbrt} and L{sqrt3}. 

300 ''' 

301 return abs(x).fpow(_2_3rd) if _isFsum_2Tuple(x) else _cbrt(x**2) 

302 

303 

304def euclid(x, y, *x0_y0, **half): 

305 '''I{Appoximate} the norm M{hypot(B{x}, B{y})} by M{max(abs(B{x}), 

306 abs(B{y})) + min(abs(B{x}), abs(B{y})) * 0.4142...}. 

307 

308 @arg x: X component (C{scalar}, an L{Fsum} or L{Fsum2Tuple}). 

309 @arg y: Y component (C{scalar}, an L{Fsum} or L{Fsum2Tuple}). 

310 @arg x0_y0: Optional reference C{(x0, y0)} (each C{scalar}, an 

311 L{Fsum} or L{Fsum2Tuple}). 

312 @kwarg half: Use C{B{half}=True} to apply C{0.5} instead of 

313 C{sqrt(2) - 1} (C{bool}). 

314 

315 @return: Appoximate norm (C{float} or L{Fsum}). 

316 ''' 

317 x, y = _map0(abs, x, y, *x0_y0) # NOT fabs! 

318 if x < y: 

319 x, y = y, x 

320 y *= _half(**half) if half else _0_4142 # _0_5 before 20.10.02 

321 return x + y 

322 

323 

324def euclid_(*xs, **half): 

325 '''I{Appoximate} the norm M{sqrt(sum(x**2 for x in xs))} by cascaded 

326 L{euclid}. 

327 

328 @arg xs: X values (each C{scalar}, an L{Fsum} or L{Fsum2Tuple}), 

329 all positional. 

330 @kwarg half: Use C{B{half}=True} to apply C{0.5} instead of 

331 C{sqrt(2) - 1} (C{bool}). 

332 

333 @return: Appoximate norm (C{float} or L{Fsum}). 

334 

335 @see: Function L{euclid}. 

336 ''' 

337 e = _0_0 

338 f = _half(**half) 

339 for x in sorted(map(abs, xs)): # NOT fabs, reverse=True! 

340 # e = euclid(x, e) 

341 if x: 

342 if e < x: 

343 e, x = x, e 

344 x *= f 

345# s = e + x 

346# if e < x: # like .fsums._2sum 

347# x -= s # e = (x - s) + e 

348# else: 

349# e -= s # e = (e - s) + x 

350 e += x 

351# e += s 

352 return e 

353 

354 

355def facos1(x): 

356 '''Fast approximation of L{pygeodesy.acos1}C{(B{x})}, scalar. 

357 

358 @see: U{ShaderFastLibs.h<https://GitHub.com/michaldrobot/ 

359 ShaderFastLibs/blob/master/ShaderFastMathLib.h>}. 

360 ''' 

361 a = fabs(x) 

362 if a < EPS0: 

363 r = PI_2 

364 elif a < EPS1: 

365 r = _fast(-a, 1.5707288, 0.2121144, 0.0742610, 0.0187293) 

366 r *= sqrt(_1_0 - a) 

367 if x < 0: 

368 r = PI - r 

369 else: 

370 r = PI if x < 0 else _0_0 

371 return r 

372 

373 

374def fasin1(x): # PYCHOK no cover 

375 '''Fast approximation of L{pygeodesy.asin1}C{(B{x})}, scalar. 

376 

377 @see: L{facos1}. 

378 ''' 

379 return PI_2 - facos1(x) 

380 

381 

382def _fast(x, *cs): 

383 '''(INTERNAL) Horner form for C{facos1} and C{fatan1}. 

384 ''' 

385 h = 0 

386 for c in reversed(cs): 

387 h = _fma(x, h, c) if h else c 

388 return h 

389 

390 

391def fatan(x): 

392 '''Fast approximation of C{atan(B{x})}, scalar. 

393 ''' 

394 a = fabs(x) 

395 if a < _1_0: 

396 r = fatan1(a) if a else _0_0 

397 elif a > _1_0: 

398 r = PI_2 - fatan1(_1_0 / a) # == fatan2(a, _1_0) 

399 else: 

400 r = PI_4 

401 if x < 0: # copysign0(r, x) 

402 r = -r 

403 return r 

404 

405 

406def fatan1(x): 

407 '''Fast approximation of C{atan(B{x})} for C{0 <= B{x} < 1}, I{unchecked}. 

408 

409 @see: U{ShaderFastLibs.h<https://GitHub.com/michaldrobot/ShaderFastLibs/ 

410 blob/master/ShaderFastMathLib.h>} and U{Efficient approximations 

411 for the arctangent function<http://www-Labs.IRO.UMontreal.CA/ 

412 ~mignotte/IFT2425/Documents/EfficientApproximationArctgFunction.pdf>}, 

413 IEEE Signal Processing Magazine, 111, May 2006. 

414 ''' 

415 # Eq (9): PI_4 * x - x * (abs(x) - 1) * (0.2447 + 0.0663 * abs(x)), for -1 < x < 1 

416 # == PI_4 * x - (x**2 - x) * (0.2447 + 0.0663 * x), for 0 < x < 1 

417 # == x * (1.0300981633974482 + x * (-0.1784 - x * 0.0663)) 

418 return _fast(x, _0_0, 1.0300981634, -0.1784, -0.0663) 

419 

420 

421def fatan2(y, x): 

422 '''Fast approximation of C{atan2(B{y}, B{x})}, scalar. 

423 

424 @see: U{fastApproximateAtan(x, y)<https://GitHub.com/CesiumGS/cesium/blob/ 

425 master/Source/Shaders/Builtin/Functions/fastApproximateAtan.glsl>} 

426 and L{fatan1}. 

427 ''' 

428 a, b = fabs(x), fabs(y) 

429 if b > a: 

430 r = (PI_2 - fatan1(a / b)) if a else PI_2 

431 elif a > b: 

432 r = fatan1(b / a) if b else _0_0 

433 elif a: # a == b != 0 

434 r = PI_4 

435 else: # a == b == 0 

436 return _0_0 

437 if x < 0: 

438 r = PI - r 

439 if y < 0: # copysign0(r, y) 

440 r = -r 

441 return r 

442 

443 

444def favg(a, b, f=_0_5, nonfinites=True): 

445 '''Return the precise average of two values. 

446 

447 @arg a: One (C{scalar}, an L{Fsum} or L{Fsum2Tuple}). 

448 @arg b: Other (C{scalar}, an L{Fsum} or L{Fsum2Tuple}). 

449 @kwarg f: Optional fraction (C{float}). 

450 @kwarg nonfinites: Optional setting, see function L{fma}. 

451 

452 @return: M{a + f * (b - a)} (C{float}). 

453 ''' 

454 F = fma(f, (b - a), a, nonfinites=nonfinites) 

455 return float(F) 

456 

457 

458def fdot(xs, *ys, **start_f2product_nonfinites): 

459 '''Return the precision dot product M{start + sum(xs[i] * ys[i] for i in range(len(xs)))}. 

460 

461 @arg xs: Iterable of values (each C{scalar}, an L{Fsum} or L{Fsum2Tuple}). 

462 @arg ys: Other values (each C{scalar}, an L{Fsum} or L{Fsum2Tuple}), all positional. 

463 @kwarg start_f2product_nonfinites: Optional bias C{B{start}=0} (C{scalar}, an 

464 L{Fsum} or L{Fsum2Tuple}) and settings C{B{f2product}=None} (C{bool}) 

465 and C{B{nonfinites=True}} (C{bool}), see class L{Fsum<Fsum.__init__>}. 

466 

467 @return: Dot product (C{float}). 

468 

469 @raise LenError: Unequal C{len(B{xs})} and C{len(B{ys})}. 

470 

471 @see: Class L{Fdot}, U{Algorithm 5.10 B{DotK} 

472 <https://www.TUHH.De/ti3/paper/rump/OgRuOi05.pdf>} and function 

473 C{math.sumprod} in Python 3.12 and later. 

474 ''' 

475 D = Fdot(xs, *ys, **_xkwds(start_f2product_nonfinites, nonfinites=True)) 

476 return float(D) 

477 

478 

479def fdot_(*xys, **start_f2product_nonfinites): 

480 '''Return the (precision) dot product M{start + sum(xys[i] * xys[i+1] for i in range(0, len(xys), B{2}))}. 

481 

482 @arg xys: Pairwise values (each C{scalar}, an L{Fsum} or L{Fsum2Tuple}), all positional. 

483 

484 @see: Function L{fdot} for further details. 

485 

486 @return: Dot product (C{float}). 

487 ''' 

488 D = Fdot_(*xys, **_xkwds(start_f2product_nonfinites, nonfinites=True)) 

489 return float(D) 

490 

491 

492def fdot3(xs, ys, zs, **start_f2product_nonfinites): 

493 '''Return the (precision) dot product M{start + sum(xs[i] * ys[i] * zs[i] for i in range(len(xs)))}. 

494 

495 @arg xs: X values iterable (each C{scalar}, an L{Fsum} or L{Fsum2Tuple}). 

496 @arg ys: Y values iterable (each C{scalar}, an L{Fsum} or L{Fsum2Tuple}). 

497 @arg zs: Z values iterable (each C{scalar}, an L{Fsum} or L{Fsum2Tuple}). 

498 

499 @see: Function L{fdot} for further details. 

500 

501 @return: Dot product (C{float}). 

502 

503 @raise LenError: Unequal C{len(B{xs})}, C{len(B{ys})} and/or C{len(B{zs})}. 

504 ''' 

505 n = len(xs) 

506 if not n == len(ys) == len(zs): 

507 raise LenError(fdot3, xs=n, ys=len(ys), zs=len(zs)) 

508 

509 D = Fdot((), **_xkwds(start_f2product_nonfinites, nonfinites=True)) 

510 kwds = dict(f2product=D.f2product(), nonfinites=D.nonfinites()) 

511 _f = Fsum(**kwds) 

512 D = D._facc(_f(x).f2mul_(y, z, **kwds) for x, y, z in zip(xs, ys, zs)) 

513 return float(D) 

514 

515 

516if _zip is zip: # Python 3.9- 

517 _fdotf = fdot 

518else: 

519 from pygeodesy.fsums import _fsum # math.fsum 

520 

521 def _fdotf(xs, *ys): # in .datums, .ecef 

522 '''(INTERNAL) Dot product for C{float} tuples of matching C{len}gths. 

523 ''' 

524 return _fsum(x * y for x, y in _zip(xs, ys)) # strict=True 

525 

526 

527def fhorner(x, *cs, **incx): 

528 '''Horner form evaluation of polynomial M{sum(cs[i] * x**i for i=0..n)} as 

529 in- or decreasing exponents M{sum(... i=n..0)}, where C{n = len(cs) - 1}. 

530 

531 @return: Horner sum (C{float}). 

532 

533 @see: Class L{Fhorner<Fhorner.__init__>} for further details. 

534 ''' 

535 H = Fhorner(x, *cs, **incx) 

536 return float(H) 

537 

538 

539def fidw(xs, ds, beta=2): 

540 '''Interpolate using U{Inverse Distance Weighting 

541 <https://WikiPedia.org/wiki/Inverse_distance_weighting>} (IDW). 

542 

543 @arg xs: Known values (each C{scalar}, an L{Fsum} or L{Fsum2Tuple}). 

544 @arg ds: Non-negative distances (each C{scalar}, an L{Fsum} or 

545 L{Fsum2Tuple}). 

546 @kwarg beta: Inverse distance power (C{int}, 0, 1, 2, or 3). 

547 

548 @return: Interpolated value C{x} (C{float}). 

549 

550 @raise LenError: Unequal or zero C{len(B{ds})} and C{len(B{xs})}. 

551 

552 @raise TypeError: An invalid B{C{ds}} or B{C{xs}}. 

553 

554 @raise ValueError: Invalid B{C{beta}}, negative B{C{ds}} or 

555 weighted B{C{ds}} below L{EPS}. 

556 

557 @note: Using C{B{beta}=0} returns the mean of B{C{xs}}. 

558 ''' 

559 n, xs = len2(xs) 

560 if n > 1: 

561 b = -Int_(beta=beta, low=0, high=3) 

562 if b < 0: 

563 try: # weighted 

564 _d, W, X = (Fsum() for _ in range(3)) 

565 for i, d in enumerate(_xiterable(ds)): 

566 x = xs[i] 

567 D = _d(d) 

568 if D < EPS0: 

569 if D < 0: 

570 raise ValueError(_negative_) 

571 x = float(x) 

572 i = n 

573 break 

574 if D.fpow(b): 

575 W += D 

576 X += D.fmul(x) 

577 else: 

578 x = X.fover(W, raiser=False) 

579 i += 1 # len(xs) >= len(ds) 

580 except IndexError: 

581 i += 1 # len(xs) < i < len(ds) 

582 except Exception as X: 

583 _I = Fmt.INDEX 

584 raise _xError(X, _I(xs=i), x, # PYLINT E1120 

585 _I(ds=i), d) # PYLINT E1120 

586 else: # b == 0 

587 x = fsum(xs) / n # fmean(xs) 

588 i = n 

589 elif n: 

590 x = float(xs[0]) 

591 i = n 

592 else: 

593 x = _0_0 

594 i, _ = len2(ds) 

595 if i != n: 

596 raise LenError(fidw, xs=n, ds=i) 

597 return x 

598 

599 

600try: 

601 from math import fma as _fma # in .resections 

602 

603 def _fhornerf(x, *cs, **incx): 

604 '''(INTERNAL) Horner form for C{float} coefficients C{cs} and C{x} 

605 and C{B{incx}=True} in- or decreasing with exponents=. 

606 ''' 

607 h = _0_0 

608 if cs: 

609 if _xkwds_get(incx, incx=True): 

610 cs = reversed(cs) 

611 for c in cs: 

612 h = _fma(x, h, c) if h else c 

613 return h 

614 

615except ImportError: # PYCHOK DSPACE! 

616 _fhornerf = fhorner # PYCHOK redef 

617 

618 def _fma(x, y, z): # no need for accuracy 

619 return x * y + z 

620 

621 

622def fma(x, y, z, **nonfinites): # **raiser 

623 '''Fused-multiply-add, using C{math.fma(x, y, z)} in Python 3.13+ 

624 or an equivalent implementation. 

625 

626 @arg x: Multiplicand (C{scalar}, an L{Fsum} or L{Fsum2Tuple}). 

627 @arg y: Multiplier (C{scalar}, an L{Fsum} or L{Fsum2Tuple}). 

628 @arg z: Addend (C{scalar}, an L{Fsum} or L{Fsum2Tuple}). 

629 @kwarg nonfinites: Use C{B{nonfinites}=True} or C{=False}, 

630 to override default L{nonfiniterrors} 

631 (C{bool}), see method L{Fsum.fma}. 

632 

633 @return: C{(x * y) + z} (C{float} or L{Fsum}). 

634 ''' 

635 F, raiser = _Fm2(x, **nonfinites) 

636 return F.fma(y, z, **raiser).as_iscalar 

637 

638 

639def _Fm2(x, nonfinites=None, **raiser): 

640 '''(INTERNAL) Handle C{fma} and C{f2mul} DEPRECATED C{raiser=False}. 

641 ''' 

642 return Fsum(x, nonfinites=nonfinites), raiser 

643 

644 

645def fmean(xs, nonfinites=True): 

646 '''Compute the accurate mean M{sum(xs) / len(xs)}. 

647 

648 @arg xs: Values (each C{scalar}, or L{Fsum} or L{Fsum2Tuple}). 

649 

650 @return: Mean value (C{float}). 

651 

652 @raise LenError: No B{C{xs}} values. 

653 

654 @raise OverflowError: Partial C{2sum} overflow. 

655 ''' 

656 n, xs = len2(xs) 

657 if n < 1: 

658 raise LenError(fmean, xs=xs) 

659 M = Fsum(*xs, nonfinites=nonfinites) 

660 return M.fover(n) if n > 1 else float(M) 

661 

662 

663def fmean_(*xs, **nonfinites): 

664 '''Compute the accurate mean M{sum(xs) / len(xs)}. 

665 

666 @see: Function L{fmean} for further details. 

667 ''' 

668 return fmean(xs, **nonfinites) 

669 

670 

671def f2mul_(x, *ys, **nonfinites): # **raiser 

672 '''Cascaded, accurate multiplication C{B{x} * B{y} * B{y} ...} for all B{C{ys}}. 

673 

674 @arg x: Multiplicand (C{scalar}, an L{Fsum} or L{Fsum2Tuple}). 

675 @arg ys: Multipliers (each C{scalar}, an L{Fsum} or L{Fsum2Tuple}), all 

676 positional. 

677 @kwarg nonfinites: Use C{B{nonfinites}=True} or C{=False}, to override default 

678 L{nonfiniterrors} (C{bool}), see method L{Fsum.f2mul_}. 

679 

680 @return: The cascaded I{TwoProduct} (C{float}, C{int} or L{Fsum}). 

681 

682 @see: U{Equations 2.3<https://www.TUHH.De/ti3/paper/rump/OzOgRuOi06.pdf>} 

683 ''' 

684 F, raiser = _Fm2(x, **nonfinites) 

685 return F.f2mul_(*ys, **raiser).as_iscalar 

686 

687 

688def fpolynomial(x, *cs, **over_f2product_nonfinites): 

689 '''Evaluate the polynomial M{sum(cs[i] * x**i for i=0..len(cs)) [/ over]}. 

690 

691 @kwarg over_f2product_nonfinites: Optional final divisor C{B{over}=None} 

692 (I{non-zero} C{scalar}) and other settings, see class 

693 L{Fpolynomial<Fpolynomial.__init__>}. 

694 

695 @return: Polynomial value (C{float} or L{Fpolynomial}). 

696 ''' 

697 d, kwds = _xkwds_pop2(over_f2product_nonfinites, over=0) 

698 P = Fpolynomial(x, *cs, **kwds) 

699 return P.fover(d) if d else float(P) 

700 

701 

702def fpowers(x, n, alts=0): 

703 '''Return a series of powers M{[x**i for i=1..n]}, note I{1..!} 

704 

705 @arg x: Value (C{scalar}, an L{Fsum} or L{Fsum2Tuple}). 

706 @arg n: Highest exponent (C{int}). 

707 @kwarg alts: Only alternating powers, starting with this 

708 exponent (C{int}). 

709 

710 @return: Tuple of powers of B{C{x}} (each C{type(B{x})}). 

711 

712 @raise TypeError: Invalid B{C{x}} or B{C{n}} not C{int}. 

713 

714 @raise ValueError: Non-finite B{C{x}} or invalid B{C{n}}. 

715 ''' 

716 if not isint(n): 

717 raise _IsnotError(typename(int), n=n) 

718 elif n < 1: 

719 raise _ValueError(n=n) 

720 

721 p = x if isscalar(x) or _isFsum_2Tuple(x) else _2float(x=x) 

722 ps = tuple(_powers(p, n)) 

723 

724 if alts > 0: # x**2, x**4, ... 

725 # ps[alts-1::2] chokes PyChecker 

726 ps = ps[slice(alts-1, None, 2)] 

727 

728 return ps 

729 

730 

731try: 

732 from math import prod as fprod # PYLINT W0611 Python 3.8 

733except ImportError: 

734 

735 def fprod(xs, start=1): 

736 '''Iterable product, like C{math.prod} or C{numpy.prod}. 

737 

738 @arg xs: Iterable of values to be multiplied (each 

739 C{scalar}, an L{Fsum} or L{Fsum2Tuple}). 

740 @kwarg start: Initial value, also the value returned 

741 for an empty B{C{xs}} (C{scalar}). 

742 

743 @return: The product (C{float} or L{Fsum}). 

744 

745 @see: U{NumPy.prod<https://docs.SciPy.org/doc/ 

746 numpy/reference/generated/numpy.prod.html>}. 

747 ''' 

748 return freduce(_operator.mul, xs, start) 

749 

750 

751def frandoms(n, seeded=None): 

752 '''Generate C{n} (long) lists of random C{floats}. 

753 

754 @arg n: Number of lists to generate (C{int}, non-negative). 

755 @kwarg seeded: If C{scalar}, use C{random.seed(B{seeded})} or 

756 if C{True}, seed using today's C{year-day}. 

757 

758 @see: U{Hettinger<https://GitHub.com/ActiveState/code/tree/master/recipes/ 

759 Python/393090_Binary_floating_point_summatiaccurate_full/recipe-393090.py>}. 

760 ''' 

761 from random import gauss, random, seed, shuffle 

762 

763 if seeded is None: 

764 pass 

765 elif seeded and isbool(seeded): 

766 from time import localtime 

767 seed(localtime().tm_yday) 

768 elif isscalar(seeded): 

769 seed(seeded) 

770 

771 c = (7, 1e100, -7, -1e100, -9e-20, 8e-20) * 7 

772 for _ in range(n): 

773 s = 0 

774 t = list(c) 

775 _a = t.append 

776 for _ in range(n * 8): 

777 v = gauss(0, random())**7 - s 

778 _a(v) 

779 s += v 

780 shuffle(t) 

781 yield t 

782 

783 

784def frange(start, number, step=1): 

785 '''Generate a range of C{float}s. 

786 

787 @arg start: First value (C{float}). 

788 @arg number: The number of C{float}s to generate (C{int}). 

789 @kwarg step: Increment value (C{float}). 

790 

791 @return: A generator (C{float}s). 

792 

793 @see: U{NumPy.prod<https://docs.SciPy.org/doc/ 

794 numpy/reference/generated/numpy.arange.html>}. 

795 ''' 

796 if not isint(number): 

797 raise _IsnotError(typename(int), number=number) 

798 for i in range(number): 

799 yield start + (step * i) 

800 

801 

802try: 

803 from functools import reduce as freduce 

804except ImportError: 

805 try: 

806 freduce = reduce # PYCHOK expected 

807 except NameError: # Python 3+ 

808 

809 def freduce(f, xs, *start): 

810 '''For missing C{functools.reduce}. 

811 ''' 

812 if start: 

813 r = v = start[0] 

814 else: 

815 r, v = 0, MISSING 

816 for v in xs: 

817 r = f(r, v) 

818 if v is MISSING: 

819 raise _TypeError(xs=(), start=MISSING) 

820 return r 

821 

822 

823def fremainder(x, y): 

824 '''Remainder in range C{[-B{y / 2}, B{y / 2}]}. 

825 

826 @arg x: Numerator (C{scalar}). 

827 @arg y: Modulus, denominator (C{scalar}). 

828 

829 @return: Remainder (C{scalar}, preserving signed 

830 0.0) or C{NAN} for any non-finite B{C{x}}. 

831 

832 @raise ValueError: Infinite or near-zero B{C{y}}. 

833 

834 @see: I{Karney}'s U{Math.remainder<https://PyPI.org/ 

835 project/geographiclib/>} and Python 3.7+ 

836 U{math.remainder<https://docs.Python.org/3/ 

837 library/math.html#math.remainder>}. 

838 ''' 

839 # with Python 2.7.16 and 3.7.3 on macOS 10.13.6 and 

840 # with Python 3.10.2 on macOS 12.2.1 M1 arm64 native 

841 # fmod( 0, 360) == 0.0 

842 # fmod( 360, 360) == 0.0 

843 # fmod(-0, 360) == 0.0 

844 # fmod(-0.0, 360) == -0.0 

845 # fmod(-360, 360) == -0.0 

846 # however, using the % operator ... 

847 # 0 % 360 == 0 

848 # 360 % 360 == 0 

849 # 360.0 % 360 == 0.0 

850 # -0 % 360 == 0 

851 # -360 % 360 == 0 == (-360) % 360 

852 # -0.0 % 360 == 0.0 == (-0.0) % 360 

853 # -360.0 % 360 == 0.0 == (-360.0) % 360 

854 

855 # On Windows 32-bit with python 2.7, math.fmod(-0.0, 360) 

856 # == +0.0. This fixes this bug. See also Math::AngNormalize 

857 # in the C++ library, Math.sincosd has a similar fix. 

858 if isfinite(x): 

859 try: 

860 r = remainder(x, y) if x else x 

861 except Exception as e: 

862 raise _xError(e, unstr(fremainder, x, y)) 

863 else: # handle x INF and NINF as NAN 

864 r = NAN 

865 return r 

866 

867 

868def _half(half=False): 

869 return _0_5 if half else _0_4142 

870 

871 

872if _MODS.sys_version_info2 < (3, 8): # PYCHOK no cover 

873 from math import hypot # OK in Python 3.7- 

874 

875 def hypot_(*xs): 

876 '''Compute the norm M{sqrt(sum(x**2 for x in xs))}. 

877 

878 Similar to Python 3.8+ n-dimension U{math.hypot 

879 <https://docs.Python.org/3.8/library/math.html#math.hypot>}, 

880 but exceptions, C{nan} and C{infinite} values are 

881 handled differently. 

882 

883 @arg xs: X arguments (C{scalar}s), all positional. 

884 

885 @return: Norm (C{float}). 

886 

887 @raise OverflowError: Partial C{2sum} overflow. 

888 

889 @raise ValueError: Invalid or no B{C{xs}} values. 

890 

891 @note: The Python 3.8+ Euclidian distance U{math.dist 

892 <https://docs.Python.org/3.8/library/math.html#math.dist>} 

893 between 2 I{n}-dimensional points I{p1} and I{p2} can be 

894 computed as M{hypot_(*((c1 - c2) for c1, c2 in zip(p1, p2)))}, 

895 provided I{p1} and I{p2} have the same, non-zero length I{n}. 

896 ''' 

897 return float(_Hypot(*xs)) 

898 

899elif _MODS.sys_version_info2 < (3, 10): # PYCHOK no cover 

900 # In Python 3.8 and 3.9 C{math.hypot} is inaccurate, see 

901 # U{agdhruv<https://GitHub.com/geopy/geopy/issues/466>}, 

902 # U{cffk<https://Bugs.Python.org/issue43088>} and module 

903 # U{geomath.py<https://PyPI.org/project/geographiclib/1.52>} 

904 

905 def hypot(x, y): 

906 '''Compute the norm M{sqrt(x**2 + y**2)}. 

907 

908 @arg x: X argument (C{scalar}). 

909 @arg y: Y argument (C{scalar}). 

910 

911 @return: C{sqrt(B{x}**2 + B{y}**2)} (C{float}). 

912 ''' 

913 return float(_Hypot(x, y)) 

914 

915 from math import hypot as hypot_ # PYCHOK in Python 3.8 and 3.9 

916else: 

917 from math import hypot # PYCHOK in Python 3.10+ 

918 hypot_ = hypot 

919 

920 

921def _Hypot(*xs): 

922 '''(INTERNAL) Substitute for inaccurate C{math.hypot}. 

923 ''' 

924 return Fhypot(*xs, nonfinites=True, raiser=False) # f2product=True 

925 

926 

927def hypot1(x): 

928 '''Compute the norm M{sqrt(1 + x**2)}. 

929 

930 @arg x: Argument (C{scalar} or L{Fsum} or L{Fsum2Tuple}). 

931 

932 @return: Norm (C{float} or L{Fhypot}). 

933 ''' 

934 h = _1_0 

935 if x: 

936 if _isFsum_2Tuple(x): 

937 h = _Hypot(h, x) 

938 h = float(h) 

939 else: 

940 h = hypot(h, x) 

941 return h 

942 

943 

944def hypot2(x, y, *x0_y0): 

945 '''Compute the I{squared} norm M{x**2 + y**2}. 

946 

947 @arg x: X (C{scalar}, an L{Fsum} or L{Fsum2Tuple}). 

948 @arg y: Y (C{scalar}, an L{Fsum} or L{Fsum2Tuple}). 

949 @arg x0_y0: Optional reference C{(x0, y0)} (each C{scalar}, 

950 an L{Fsum} or L{Fsum2Tuple}). 

951 

952 @return: C{B{x}**2 + B{y}**2} (C{float}). 

953 ''' 

954 x, y = _map0(abs, x, y, *x0_y0) # NOT fabs! 

955 if x < y: 

956 x, y = y, x 

957 h2 = x**2 

958 if h2 and y: 

959 h2 *= (y / x)**2 + _1_0 

960 return float(h2) 

961 

962 

963def hypot2_(*xs): 

964 '''Compute the I{squared} norm C{fsum(x**2 for x in B{xs})}. 

965 

966 @arg xs: Components (each C{scalar}, an L{Fsum} or 

967 L{Fsum2Tuple}), all positional. 

968 

969 @return: Squared norm (C{float}). 

970 

971 @see: Class L{Fpowers} for further details. 

972 ''' 

973 h2 = float(max(map(abs, xs))) if xs else _0_0 

974 if h2: # and isfinite(h2) 

975 _h = _1_0 / h2 

976 xs = ((x * _h) for x in xs) 

977 H2 = Fpowers(2, *xs, nonfinites=True) # f2product=True 

978 h2 = H2.fover(_h**2) 

979 return h2 

980 

981 

982def _map0(_f, x, y, x0=_0_0, y0=_0_0, *unused): # PYLINT W1113 

983 return _f(x - x0), _f(y - y0) 

984 

985 

986def norm2(x, y, *x0_y0): 

987 '''Normalize a 2-dimensional vector. 

988 

989 @arg x: X component (C{scalar}, an L{Fsum} or L{Fsum2Tuple}). 

990 @arg y: Y component (C{scalar}, an L{Fsum} or L{Fsum2Tuple}). 

991 @arg x0_y0: Optional reference C{(x0, y0)} (each C{scalar}, 

992 an L{Fsum} or L{Fsum2Tuple}). 

993 

994 @return: 2-Tuple C{(x, y)}, normalized. 

995 

996 @raise ValueError: Invalid B{C{x}} or B{C{y}}. 

997 ''' 

998 try: 

999 h = None 

1000 x, y = _map0(float, x, y, *x0_y0) 

1001 h = hypot(x, y) 

1002 if h: 

1003 t = (x / h), (y / h) 

1004 else: 

1005 t = (_copysign_0_0(x), # pass? 

1006 _copysign_0_0(y)) 

1007 except Exception as X: 

1008 raise _xError(X, x=x, y=y, h=h) 

1009 return t 

1010 

1011 

1012def norm_(*xs): 

1013 '''Normalize the components of an n-dimensional vector. 

1014 

1015 @arg xs: Components (each C{scalar}, an L{Fsum} or 

1016 L{Fsum2Tuple}), all positional. 

1017 

1018 @return: Yield each component, normalized. 

1019 

1020 @raise ValueError: Invalid or insufficent B{C{xs}} 

1021 or zero norm. 

1022 ''' 

1023 try: 

1024 i = h = None 

1025 x = xs 

1026 h = hypot_(*xs) 

1027 _h = (_1_0 / h) if h else _0_0 

1028 for i, x in enumerate(xs): 

1029 yield x * _h 

1030 except Exception as X: 

1031 raise _xsError(X, xs, i, x, h=h) # PYLINT E0601 

1032 

1033 

1034def polar2(x, y, *x0_y0): 

1035 '''Return 2-tuple C{(length, angle)} with C{angle} in radians M{[0..+PI2)}. 

1036 

1037 @arg x: X (C{scalar}, an L{Fsum} or L{Fsum2Tuple}). 

1038 @arg y: Y (C{scalar}, an L{Fsum} or L{Fsum2Tuple}). 

1039 @arg x0_y0: Optional reference C{(x0, y0)} (each C{scalar}, an L{Fsum} or L{Fsum2Tuple}). 

1040 

1041 @note: Use C{polar(B{y}, B{x}, *B{yx0})} to get the angle as C{bearing} from North. 

1042 ''' 

1043 x, y = _map0(float, x, y, *x0_y0) 

1044 return hypot(x, y), _MODS.utily.atan2p(y, x) 

1045 

1046 

1047def polar2d(x, y, *x0_y0): 

1048 '''Return 2-tuple C{(length, angle)} with C{angle} in degrees M{[0..+360)}. 

1049 

1050 @arg x: X (C{scalar}, an L{Fsum} or L{Fsum2Tuple}). 

1051 @arg y: Y (C{scalar}, an L{Fsum} or L{Fsum2Tuple}). 

1052 @arg x0_y0: Optional reference C{(x0, y0)} (each C{scalar}, an L{Fsum} or L{Fsum2Tuple}). 

1053 

1054 @note: Use C{polar2d(B{y}, B{x}, *B{yx0})} to get the angle as C{bearing} from North. 

1055 ''' 

1056 x, y = _map0(float, x, y, *x0_y0) 

1057 return hypot(x, y), _MODS.utily.atan2b(y, x) 

1058 

1059 

1060def _powers(x, n): 

1061 '''(INTERNAL) Yield C{x**i for i=1..n}. 

1062 ''' 

1063 p = 1 # type(p) == type(x) 

1064 for _ in range(n): 

1065 p *= x 

1066 yield p 

1067 

1068 

1069def _root(x, p, where): 

1070 '''(INTERNAL) Raise C{x} to power C{0 <= p < 1}. 

1071 ''' 

1072 try: 

1073 if x > 0: 

1074 r = Fsum(f2product=True, nonfinites=True)(x) 

1075 return r.fpow(p).as_iscalar 

1076 elif x < 0: 

1077 raise ValueError(_negative_) 

1078 except Exception as X: 

1079 raise _xError(X, unstr(where, x)) 

1080 return _0_0 if p else _1_0 # x == 0 

1081 

1082 

1083def sqrt0(x, Error=None): 

1084 '''Return the square root C{sqrt(B{x})} iff C{B{x} > }L{EPS02}, 

1085 preserving C{type(B{x})}. 

1086 

1087 @arg x: Value (C{scalar}, an L{Fsum} or L{Fsum2Tuple}). 

1088 @kwarg Error: Error to raise for negative B{C{x}}. 

1089 

1090 @return: Square root (C{float} or L{Fsum}) or C{0.0}. 

1091 

1092 @raise TypeeError: Invalid B{C{x}}. 

1093 

1094 @note: Any C{B{x} < }L{EPS02} I{including} C{B{x} < 0} 

1095 returns C{0.0}. 

1096 ''' 

1097 if Error and x < 0: 

1098 raise Error(unstr(sqrt0, x)) 

1099 return _root(x, _0_5, sqrt0) if x > EPS02 else ( 

1100 _0_0 if x < EPS02 else EPS0) 

1101 

1102 

1103def sqrt3(x): 

1104 '''Return the square root, I{cubed} M{sqrt(x)**3} or M{sqrt(x**3)}, 

1105 preserving C{type(B{x})}. 

1106 

1107 @arg x: Value (C{scalar}, an L{Fsum} or L{Fsum2Tuple}). 

1108 

1109 @return: Square root I{cubed} (C{float} or L{Fsum}). 

1110 

1111 @raise TypeeError: Invalid B{C{x}}. 

1112 

1113 @raise ValueError: Negative B{C{x}}. 

1114 

1115 @see: Functions L{cbrt} and L{cbrt2}. 

1116 ''' 

1117 return _root(x, _1_5, sqrt3) 

1118 

1119 

1120def sqrt_a(h, b): 

1121 '''Compute the C{I{a}} side of a right-angled triangle from 

1122 C{sqrt(B{h}**2 - B{b}**2)}. 

1123 

1124 @arg h: Hypotenuse or outer annulus radius (C{scalar}). 

1125 @arg b: Triangle side or inner annulus radius (C{scalar}). 

1126 

1127 @return: C{copysign(I{a}, B{h})} or C{unsigned 0.0} (C{float}). 

1128 

1129 @raise TypeError: Non-scalar B{C{h}} or B{C{b}}. 

1130 

1131 @raise ValueError: If C{abs(B{h}) < abs(B{b})}. 

1132 

1133 @see: Inner tangent chord B{I{d}} of an U{annulus 

1134 <https://WikiPedia.org/wiki/Annulus_(mathematics)>} 

1135 and function U{annulus_area<https://People.SC.FSU.edu/ 

1136 ~jburkardt/py_src/geometry/geometry.py>}. 

1137 ''' 

1138 try: 

1139 if not (_isHeight(h) and _isRadius(b)): 

1140 raise TypeError(_not_scalar_) 

1141 c = fabs(h) 

1142 if c > EPS0: 

1143 s = _1_0 - (b / c)**2 

1144 if s < 0: 

1145 raise ValueError(_h_lt_b_) 

1146 a = (sqrt(s) * c) if 0 < s < 1 else (c if s else _0_0) 

1147 else: # PYCHOK no cover 

1148 b = fabs(b) 

1149 d = c - b 

1150 if d < 0: 

1151 raise ValueError(_h_lt_b_) 

1152 d *= c + b 

1153 a = sqrt(d) if d else _0_0 

1154 except Exception as x: 

1155 raise _xError(x, h=h, b=b) 

1156 return copysign0(a, h) 

1157 

1158 

1159def zcrt(x): 

1160 '''Return the 6-th, I{zenzi-cubic} root, M{x**(1 / 6)}, 

1161 preserving C{type(B{x})}. 

1162 

1163 @arg x: Value (C{scalar}, an L{Fsum} or L{Fsum2Tuple}). 

1164 

1165 @return: I{Zenzi-cubic} root (C{float} or L{Fsum}). 

1166 

1167 @see: Functions L{bqrt} and L{zqrt}. 

1168 

1169 @raise TypeeError: Invalid B{C{x}}. 

1170 

1171 @raise ValueError: Negative B{C{x}}. 

1172 ''' 

1173 return _root(x, _1_6th, zcrt) 

1174 

1175 

1176def zqrt(x): 

1177 '''Return the 8-th, I{zenzi-quartic} or I{squared-quartic} root, 

1178 M{x**(1 / 8)}, preserving C{type(B{x})}. 

1179 

1180 @arg x: Value (C{scalar}, an L{Fsum} or L{Fsum2Tuple}). 

1181 

1182 @return: I{Zenzi-quartic} root (C{float} or L{Fsum}). 

1183 

1184 @see: Functions L{bqrt} and L{zcrt}. 

1185 

1186 @raise TypeeError: Invalid B{C{x}}. 

1187 

1188 @raise ValueError: Negative B{C{x}}. 

1189 ''' 

1190 return _root(x, _0_125, zqrt) 

1191 

1192# **) MIT License 

1193# 

1194# Copyright (C) 2016-2026 -- mrJean1 at Gmail -- All Rights Reserved. 

1195# 

1196# Permission is hereby granted, free of charge, to any person obtaining a 

1197# copy of this software and associated documentation files (the "Software"), 

1198# to deal in the Software without restriction, including without limitation 

1199# the rights to use, copy, modify, merge, publish, distribute, sublicense, 

1200# and/or sell copies of the Software, and to permit persons to whom the 

1201# Software is furnished to do so, subject to the following conditions: 

1202# 

1203# The above copyright notice and this permission notice shall be included 

1204# in all copies or substantial portions of the Software. 

1205# 

1206# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS 

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