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Class L{Elliptic} transcoded from I{Charles Karney}'s C++ class U{EllipticFunction <https://GeographicLib.SourceForge.io/C++/doc/classGeographicLib_1_1EllipticFunction.html>} to pure Python, including symmetric integrals L{Elliptic.fRC}, L{Elliptic.fRD}, L{Elliptic.fRF}, L{Elliptic.fRG} and L{Elliptic.fRJ} as C{static methods}. Python method names follow the C++ member functions, I{except}: - member functions I{without arguments} are mapped to Python properties prefixed with C{"c"}, for example C{E()} is property C{cE}, - member functions with 1 or 3 arguments are renamed to Python methods starting with an C{"f"}, example C{E(psi)} to C{fE(psi)} and C{E(sn, cn, dn)} to C{fE(sn, cn, dn)}, - other Python method names conventionally start with a lower-case letter or an underscore if private. Following is a copy of I{Karney}'s U{EllipticFunction.hpp <https://GeographicLib.SourceForge.io/C++/doc/EllipticFunction_8hpp_source.html>} file C{Header}. Copyright (C) U{Charles Karney<mailto:Charles@Karney.com>} (2008-2022) and licensed under the MIT/X11 License. For more information, see the U{GeographicLib<https://GeographicLib.SourceForge.io>} documentation. B{Elliptic integrals and functions.} This provides the elliptic functions and integrals needed for C{Ellipsoid}, C{GeodesicExact}, and C{TransverseMercatorExact}. Two categories of function are provided: - functions to compute U{symmetric elliptic integrals <https://DLMF.NIST.gov/19.16.i>} - methods to compute U{Legrendre's elliptic integrals <https://DLMF.NIST.gov/19.2.ii>} and U{Jacobi elliptic functions<https://DLMF.NIST.gov/22.2>}. In the latter case, an object is constructed giving the modulus C{k} (and optionally the parameter C{alpha}). The modulus (and parameter) are always passed as squares which allows C{k} to be pure imaginary. (Confusingly, Abramowitz and Stegun call C{m = k**2} the "parameter" and C{n = alpha**2} the "characteristic".) In geodesic applications, it is convenient to separate the incomplete integrals into secular and periodic components, e.g. I{C{E(phi, k) = (2 E(k) / pi) [ phi + delta E(phi, k) ]}} where I{C{delta E(phi, k)}} is an odd periodic function with period I{C{pi}}. The computation of the elliptic integrals uses the algorithms given in U{B. C. Carlson, Computation of real or complex elliptic integrals <https://DOI.org/10.1007/BF02198293>} (also available U{here <https://ArXiv.org/pdf/math/9409227.pdf>}), Numerical Algorithms 10, 13--26 (1995) with the additional optimizations given U{here <https://DLMF.NIST.gov/19.36.i>}. The computation of the Jacobi elliptic functions uses the algorithm given in U{R. Bulirsch, Numerical Calculation of Elliptic Integrals and Elliptic Functions<https://DOI.org/10.1007/BF01397975>}, Numerische Mathematik 7, 78--90 (1965). The notation follows U{NIST Digital Library of Mathematical Functions <https://DLMF.NIST.gov>} chapters U{19<https://DLMF.NIST.gov/19>} and U{22<https://DLMF.NIST.gov/22>}. ''' # make sure int/int division yields float quotient, see .basics from __future__ import division as _; del _ # PYCHOK semicolon from pygeodesy.basics import copysign0, map2, neg # from pygeodesy.errors import _ValueError # from .fmath from pygeodesy.fmath import fdot, Fsum, hypot1, _ValueError # from pygeodesy.fsums import Fsum # from .fmath from pygeodesy.interns import EPS, INF, NN, PI, PI_2, PI_4, \ _DOT_, _EPStol as _TolJAC, _convergence_, \ _f_, _no_, _SPACE_, _0_0, _0_125, _0_25, \ _0_5, _1_0, _2_0, _N_2_0, _3_0, _4_0, \ _5_0, _6_0, _8_0, _180_0, _360_0 from pygeodesy.karney import _ALL_LAZY, _signBit # from pygeodesy.lazily import _ALL_LAZY # from .karney from pygeodesy.named import _Named, _NamedTuple, unstr from pygeodesy.props import Property_RO, _update_all # from pygeodesy.streprs import unstr # from .named from pygeodesy.units import Scalar, Scalar_ from pygeodesy.utily import sincos2, sincos2d from math import asinh, atan, atan2, ceil, cosh, floor, sin, \ sqrt, tanh __all__ = _ALL_LAZY.elliptic __version__ = '22.07.08' _delta_ = 'delta' _invokation_ = 'invokation' _1_64th = _1_0 / 64 # pow(2.0, -6) _TolRD = pow(EPS * 0.002, _0_125) # 8th root: quadquadratic?, octic?, ocrt? _TolRF = pow(EPS * 0.030, _0_125) # 4th root: biquadratic, quartic, qurt? _TolRG0 = _TolJAC * 2.7 _TRIPS = 31 # Max depth, 7 might be sufficient class _Complete(object): '''(INTERAL) Hold complete integrals. ''' def __init__(self, **kwds): self.__dict__ = kwds class Elliptic(_Named): '''Elliptic integrals and functions. @see: I{Karney}'s U{Detailed Description<https://GeographicLib.SourceForge.io/ html/classGeographicLib_1_1EllipticFunction.html#details>}. ''' _alpha2 = 0 _alphap2 = 0 _eps = EPS _k2 = 0 _kp2 = 0 def __init__(self, k2=0, alpha2=0, kp2=None, alphap2=None): '''Constructor, specifying the C{modulus} and C{parameter}. @see: Method L{Elliptic.reset} for further details. @note: If only elliptic integrals of the first and second kinds are needed, use C{B{alpha2}=0}, the default value. In that case, we have C{Π(φ, 0, k) = F(φ, k), G(φ, 0, k) = E(φ, k)} and C{H(φ, 0, k) = F(φ, k) - D(φ, k)}. ''' self.reset(k2=k2, alpha2=alpha2, kp2=kp2, alphap2=alphap2) @Property_RO def alpha2(self): '''Get α^2, the square of the parameter (C{float}). ''' return self._alpha2 @Property_RO def alphap2(self): '''Get α'^2, the square of the complementary parameter (C{float}). ''' return self._alphap2 @Property_RO def cD(self): '''Get Jahnke's complete integral C{D(k)} (C{float}), U{defined<https://DLMF.NIST.gov/19.2.E6>}. ''' return self._reset4integrals.cD @Property_RO def cE(self): '''Get the complete integral of the second kind C{E(k)} (C{float}), U{defined<https://DLMF.NIST.gov/19.2.E5>}. ''' return self._reset4integrals.cE @Property_RO def cG(self): '''Get Legendre's complete geodesic longitude integral C{G(α^2, k)} (C{float}). ''' return self._reset3integrals.cG @Property_RO def cH(self): '''Get Cayley's complete geodesic longitude difference integral C{H(α^2, k)} (C{float}). ''' return self._reset3integrals.cH @Property_RO def cK(self): '''Get the complete integral of the first kind C{K(k)} (C{float}), U{defined<https://DLMF.NIST.gov/19.2.E4>}. ''' return self._reset4integrals.cK @Property_RO def cKE(self): '''Get the difference between the complete integrals of the first and second kinds, C{K(k) − E(k)} (C{float}). ''' return self._reset4integrals.cKE @Property_RO def cPi(self): '''Get the complete integral of the third kind C{Pi(α^2, k)} (C{float}), U{defined<https://DLMF.NIST.gov/19.2.E7>}. ''' return self._reset3integrals.cPi def deltaD(self, sn, cn, dn): '''The periodic Jahnke's incomplete elliptic integral. @arg sn: sin(φ). @arg cn: cos(φ). @arg dn: sqrt(1 − k2 sin(2φ)). @return: Periodic function π D(φ, k) / (2 D(k)) - φ (C{float}). @raise EllipticError: Invalid invokation or no convergence. ''' return self._deltaX(sn, cn, dn, self.cD, self.fD) def deltaE(self, sn, cn, dn): '''The periodic incomplete integral of the second kind. @arg sn: sin(φ). @arg cn: cos(φ). @arg dn: sqrt(1 − k2 sin(2φ)). @return: Periodic function π E(φ, k) / (2 E(k)) - φ (C{float}). @raise EllipticError: Invalid invokation or no convergence. ''' return self._deltaX(sn, cn, dn, self.cE, self.fE) def deltaEinv(self, stau, ctau): '''The periodic inverse of the incomplete integral of the second kind. @arg stau: sin(τ) @arg ctau: cos(τ) @return: Periodic function E^−1(τ (2 E(k)/π), k) - τ (C{float}). @raise EllipticError: No convergence. ''' # Function is periodic with period pi t = atan2(-stau, -ctau) if _signBit(ctau) else atan2(stau, ctau) return self.fEinv(t * self.cE / PI_2) - t def deltaF(self, sn, cn, dn): '''The periodic incomplete integral of the first kind. @arg sn: sin(φ). @arg cn: cos(φ). @arg dn: sqrt(1 − k2 sin(2φ)). @return: Periodic function π F(φ, k) / (2 K(k)) - φ (C{float}). @raise EllipticError: Invalid invokation or no convergence. ''' return self._deltaX(sn, cn, dn, self.cK, self.fF) def deltaG(self, sn, cn, dn): '''Legendre's periodic geodesic longitude integral. @arg sn: sin(φ). @arg cn: cos(φ). @arg dn: sqrt(1 − k2 sin(2φ)). @return: Periodic function π G(φ, k) / (2 G(k)) - φ (C{float}). @raise EllipticError: Invalid invokation or no convergence. ''' return self._deltaX(sn, cn, dn, self.cG, self.fG) def deltaH(self, sn, cn, dn): '''Cayley's periodic geodesic longitude difference integral. @arg sn: sin(φ). @arg cn: cos(φ). @arg dn: sqrt(1 − k2 sin(2φ)). @return: Periodic function π H(φ, k) / (2 H(k)) - φ (C{float}). @raise EllipticError: Invalid invokation or no convergence. ''' return self._deltaX(sn, cn, dn, self.cH, self.fH) def deltaPi(self, sn, cn, dn): '''The periodic incomplete integral of the third kind. @arg sn: sin(φ). @arg cn: cos(φ). @arg dn: sqrt(1 − k2 sin(2φ)). @return: Periodic function π Π(φ, α2, k) / (2 Π(α2, k)) - φ (C{float}). @raise EllipticError: Invalid invokation or no convergence. ''' return self._deltaX(sn, cn, dn, self.cPi, self.fPi) def _deltaX(self, sn, cn, dn, cX, fX): '''(INTERNAL) Helper for C{.deltaD} thru C{.deltaPi}. ''' if cn is None or dn is None: n = NN(_delta_, fX.__name__[1:]) raise _callError(n, sn, cn, dn) if _signBit(cn): cn, sn = -cn, -sn return fX(sn, cn, dn) * PI_2 / cX - atan2(sn, cn) @Property_RO def eps(self): '''Get epsilon (C{float}). ''' return self._reset4integrals.eps def fD(self, phi_or_sn, cn=None, dn=None): '''Jahnke's incomplete elliptic integral in terms of Jacobi elliptic functions. @arg phi_or_sn: φ or sin(φ). @kwarg cn: C{None} or cos(φ). @kwarg dn: C{None} or sqrt(1 − k2 sin(2φ)). @return: D(φ, k) as though φ ∈ (−π, π] (C{float}), U{defined<https://DLMF.NIST.gov/19.2.E4>}. @raise EllipticError: Invalid invokation or no convergence. ''' def _fD(sn, cn, dn): r = abs(sn)**3 if r: r = _RD(self, cn**2, dn**2, _1_0, _3_0 / r) return r return self._fXf(phi_or_sn, cn, dn, self.cD, self.deltaD, _fD) def fDelta(self, sn, cn): '''The C{Delta} amplitude function. @arg sn: sin(φ). @arg cn: cos(φ). @return: sqrt(1 − k2 sin(2φ)) (C{float}). ''' k2, kp2 = self.k2, self.kp2 s = (_1_0 - k2 * sn**2) if k2 < 0 else ( (kp2 + k2 * cn**2) if k2 > 0 else kp2) return sqrt(s) if s else _0_0 def fE(self, phi_or_sn, cn=None, dn=None): '''The incomplete integral of the second kind in terms of Jacobi elliptic functions. @arg phi_or_sn: φ or sin(φ). @kwarg cn: C{None} or cos(φ). @kwarg dn: C{None} or sqrt(1 − k2 sin(2φ)). @return: E(φ, k) as though φ ∈ (−π, π] (C{float}), U{defined<https://DLMF.NIST.gov/19.2.E5>}. @raise EllipticError: Invalid invokation or no convergence. ''' def _fE(sn, cn, dn): '''(INTERNAL) Core of C{.fE}. ''' if sn: sn2, cn2, dn2 = sn**2, cn**2, dn**2 kp2, k2 = self.kp2, self.k2 if k2 <= 0: # Carlson, eq. 4.6, <https://DLMF.NIST.gov/19.25.E9> ei = _RF3(self, cn2, dn2, _1_0) if k2: ei -= _RD(self, cn2, dn2, _1_0, _3rd(k2, sn2)) elif kp2 >= 0: # <https://DLMF.NIST.gov/19.25.E10> ei = k2 * abs(cn) / dn if kp2: ei += (_RD(self, cn2, _1_0, dn2, _3rd(k2, sn2)) + _RF3(self, cn2, dn2, _1_0)) * kp2 else: # <https://DLMF.NIST.gov/19.25.E11> ei = dn / abs(cn) - _RD(self, dn2, _1_0, cn2, _3rd(kp2, sn2)) ei *= abs(sn) else: # PYCHOK no cover ei = _0_0 return ei return self._fXf(phi_or_sn, cn, dn, self.cE, self.deltaE, _fE) def fEd(self, deg): '''The incomplete integral of the second kind with the argument given in degrees. @arg deg: Angle (C{degrees}). @return: E(π B{C{deg}}/180, k) (C{float}). @raise EllipticError: No convergence. ''' if abs(deg) < _180_0: e = _0_0 else: # PYCHOK no cover e = ceil(deg / _360_0 - _0_5) deg -= e * _360_0 e *= self.cE * _4_0 sn, cn = sincos2d(deg) return self.fE(sn, cn, self.fDelta(sn, cn)) + e def fEinv(self, x): '''The inverse of the incomplete integral of the second kind. @arg x: Argument (C{float}). @return: φ = 1 / E(B{C{x}}, k), such that E(φ, k) = B{C{x}} (C{float}). @raise EllipticError: No convergence. ''' E2 = self.cE * _2_0 n = floor(x / E2 + _0_5) y = x - E2 * n # y now in [-ec, ec) # linear approximation phi = PI * y / E2 # phi in [-pi/2, pi/2) Phi = Fsum(phi) # first order correction phi = Phi.fsum_(self.eps * sin(phi * _2_0) / _N_2_0) # For kp2 close to zero use asin(x/.cE) or J. P. Boyd, # Applied Math. and Computation 218, 7005-7013 (2012) # <https://DOI.org/10.1016/j.amc.2011.12.021> Phi_fsum2_ = Phi.fsum2_ fE = self.fE _sncndnPhi = self._sncndnPhi self._iteration = 0 # aggregate for i in range(1, _TRIPS): # GEOGRAPHICLIB_PANIC sn, cn, dn = _sncndnPhi(phi) phi, e = Phi_fsum2_((y - fE(sn, cn, dn)) / dn) if abs(e) < _TolJAC: self._iteration += i break else: # PYCHOK no cover raise _convergenceError(_TolJAC, self.fEinv, x) return Phi.fsum_(n * PI) if n else phi def fF(self, phi_or_sn, cn=None, dn=None): '''The incomplete integral of the first kind in terms of Jacobi elliptic functions. @arg phi_or_sn: φ or sin(φ). @kwarg cn: C{None} or cos(φ). @kwarg dn: C{None} or sqrt(1 − k2 sin(2φ)). @return: F(φ, k) as though φ ∈ (−π, π] (C{float}), U{defined<https://DLMF.NIST.gov/19.2.E4>}. @raise EllipticError: Invalid invokation or no convergence. ''' def _fF(sn, cn, dn): r = abs(sn) if r: r *= _RF3(self, cn**2, dn**2, _1_0) return r return self._fXf(phi_or_sn, cn, dn, self.cK, self.deltaF, _fF) def fG(self, phi_or_sn, cn=None, dn=None): '''Legendre's geodesic longitude integral in terms of Jacobi elliptic functions. @arg phi_or_sn: φ or sin(φ). @kwarg cn: C{None} or cos(φ). @kwarg dn: C{None} or sqrt(1 − k2 sin(2φ)). @return: G(φ, k) as though φ ∈ (−π, π] (C{float}). @raise EllipticError: Invalid invokation or no convergence. @note: Legendre expresses the longitude of a point on the geodesic in terms of this combination of elliptic integrals in U{Exercices de Calcul Intégral, Vol 1 (1811), p 181<https://Books.Google.com/books?id= riIOAAAAQAAJ&pg=PA181>}. @see: U{Geodesics in terms of elliptic integrals<https:// GeographicLib.SourceForge.io/html/geodesic.html#geodellip>} for the expression for the longitude in terms of this function. ''' return self._fXa(phi_or_sn, cn, dn, self.alpha2 - self.k2, self.cG, self.deltaG) def fH(self, phi_or_sn, cn=None, dn=None): '''Cayley's geodesic longitude difference integral in terms of Jacobi elliptic functions. @arg phi_or_sn: φ or sin(φ). @kwarg cn: C{None} or cos(φ). @kwarg dn: C{None} or sqrt(1 − k2 sin(2φ)). @return: H(φ, k) as though φ ∈ (−π, π] (C{float}). @raise EllipticError: Invalid invokation or no convergence. @note: Cayley expresses the longitude difference of a point on the geodesic in terms of this combination of elliptic integrals in U{Phil. Mag. B{40} (1870), p 333 <https://Books.Google.com/books?id=Zk0wAAAAIAAJ&pg=PA333>}. @see: U{Geodesics in terms of elliptic integrals<https:// GeographicLib.SourceForge.io/html/geodesic.html#geodellip>} for the expression for the longitude in terms of this function. ''' return self._fXa(phi_or_sn, cn, dn, -self.alphap2, self.cH, self.deltaH) def fPi(self, phi_or_sn, cn=None, dn=None): '''The incomplete integral of the third kind in terms of Jacobi elliptic functions. @arg phi_or_sn: φ or sin(φ). @kwarg cn: C{None} or cos(φ). @kwarg dn: C{None} or sqrt(1 − k2 sin(2φ)). @return: Π(φ, α2, k) as though φ ∈ (−π, π] (C{float}). @raise EllipticError: Invalid invokation or no convergence. ''' return self._fXa(phi_or_sn, cn, dn, self.alpha2, self.cPi, self.deltaPi) def _fXa(self, phi_or_sn, cn, dn, aX, cX, deltaX): '''(INTERNAL) Helper for C{.fG}, C{.fH} and C{.fPi}. ''' def _fX(sn, cn, dn): if sn: cn2, sn2, dn2 = cn**2, sn**2, dn**2 r = _RF3(self, cn2, dn2, _1_0) if aX: z = cn2 + sn2 * self.alphap2 r += _RJ(self, cn2, dn2, _1_0, z, _3rd(aX, sn2)) r *= abs(sn) else: # PYCHOK no cover r = _0_0 return r return self._fXf(phi_or_sn, cn, dn, cX, deltaX, _fX) def _fXf(self, phi_or_sn, cn, dn, cX, deltaX, fX): '''(INTERNAL) Helper for C{f.D}, C{.fE}, C{.fF} and C{._fXa}. ''' self._iteration = 0 # aggregate phi = sn = phi_or_sn if cn is dn is None: # fX(phi) call sn, cn, dn = self._sncndnPhi(phi) if abs(phi) >= PI: # PYCHOK no cover return (deltaX(sn, cn, dn) + phi) * cX / PI_2 # fall through elif cn is None or dn is None: n = NN(_f_, deltaX.__name__[5:]) raise _callError(n, sn, cn, dn) if _signBit(cn): # enforce usual trig-like symmetries xi = _2_0 * cX - fX(sn, cn, dn) elif cn > 0: xi = fX(sn, cn, dn) else: xi = cX return copysign0(xi, sn) @Property_RO def k2(self): '''Get k^2, the square of the modulus (C{float}). ''' return self._k2 @Property_RO def kp2(self): '''Get k'^2, the square of the complementary modulus (C{float}). ''' return self._kp2 def reset(self, k2=0, alpha2=0, kp2=None, alphap2=None): # MCCABE 13 '''Reset the modulus, parameter and the complementaries. @kwarg k2: Modulus squared (C{float}, NINF <= k^2 <= 1). @kwarg alpha2: Parameter squared (C{float}, NINF <= α^2 <= 1). @kwarg kp2: Complementary modulus squared (C{float}, k'^2 >= 0). @kwarg alphap2: Complementary parameter squared (C{float}, α'^2 >= 0). @raise EllipticError: Invalid B{C{k2}}, B{C{alpha2}}, B{C{kp2}} or B{C{alphap2}}. @note: The arguments must satisfy C{B{k2} + B{kp2} = 1} and C{B{alpha2} + B{alphap2} = 1}. No checking is done that these conditions are met to enable accuracy to be maintained, e.g., when C{k} is very close to unity. ''' _update_all(self, _Named.iteration._uname) self._k2 = Scalar_(k2=k2, Error=EllipticError, low=None, high=_1_0) self._kp2 = Scalar_(kp2=((_1_0 - k2) if kp2 is None else kp2), Error=EllipticError) self._alpha2 = Scalar_(alpha2=alpha2, Error=EllipticError, low=None, high=_1_0) self._alphap2 = Scalar_(alphap2=((_1_0 - alpha2) if alphap2 is None else alphap2), Error=EllipticError) # Values of complete elliptic integrals for k = 0,1 and alpha = 0,1 # K E D # k = 0: pi/2 pi/2 pi/4 # k = 1: inf 1 inf # Pi G H # k = 0, alpha = 0: pi/2 pi/2 pi/4 # k = 1, alpha = 0: inf 1 1 # k = 0, alpha = 1: inf inf pi/2 # k = 1, alpha = 1: inf inf inf # # G(0, k) = Pi(0, k) = H(1, k) = E(k) # H(0, k) = K(k) - D(k) # Pi(alpha2, 0) = G(alpha2, 0) = pi / (2 * sqrt(1 - alpha2)) # H( alpha2, 0) = pi / (2 * (sqrt(1 - alpha2) + 1)) # Pi(alpha2, 1) = inf # G( alpha2, 1) = H(alpha2, 1) = RC(1, alphap2) @Property_RO def _reset3integrals(self): '''(INTERNAL) Get the complete integrals G, H and Pi. ''' self._iteration = 0 alpha2 = self.alpha2 if alpha2: alphap2 = self.alphap2 if alphap2: kp2 = self.kp2 if kp2: # <https://DLMF.NIST.gov/19.25.E2> rj = _RJ(self, _0_0, kp2, _1_0, alphap2, _3_0) cPi = cH = cG = self.cK cG += (alpha2 - self.k2) * rj # G(alpha2, k) cH -= alphap2 * rj # H(alpha2, k) cPi += alpha2 * rj # Pi(alpha2, k) else: # PYCHOK no cover cG = cH = _RC(self, _1_0, alphap2) cPi = INF # XXX or NAN? else: # PYCHOK no cover cG = cH = cPi = INF # XXX or NAN? else: cG, cPi, kp2 = self.cE, self.cK, self.kp2 # H = K - D but this involves large cancellations if k2 is near 1. # So write (for alpha2 = 0) # H = int(cos(phi)**2/sqrt(1-k2*sin(phi)**2),phi,0,pi/2) # = 1/sqrt(1-k2) * int(sin(phi)**2/sqrt(1-k2/kp2*sin(phi)**2,...) # = 1/kp * D(i*k/kp) # and use D(k) = RD(0, kp2, 1) / 3 # so H = 1/kp * RD(0, 1/kp2, 1) / 3 # = kp2 * RD(0, 1, kp2) / 3 # using <https://DLMF.NIST.gov/19.20.E18>. Equivalently # RF(x, 1) - RD(0, x, 1)/3 = x * RD(0, 1, x)/3 for x > 0 # For k2 = 1 and alpha2 = 0, we have # H = int(cos(phi),...) = 1 cH = _RD(self, _0_0, _1_0, kp2, _3_0 / kp2) if kp2 else _1_0 return _Complete(cG=cG, cH=cH, cPi=cPi) @Property_RO def _reset4integrals(self): '''(INTERNAL) Get the complete integrals D, E, K and KE plus C{eps}. ''' k2 = self.k2 if k2: kp2 = self.kp2 if kp2: self._iteration = 0 # D(k) = (K(k) - E(k))/k2, Carlson eq.4.3 # <https://DLMF.NIST.gov/19.25.E1> cD = _RD(self, _0_0, kp2, _1_0, _3_0) # Complete elliptic integral E(k), Carlson eq. 4.2 # <https://DLMF.NIST.gov/19.25.E1> cE = _RG2(self, kp2, _1_0) # Complete elliptic integral K(k), Carlson eq. 4.1 # <https://DLMF.NIST.gov/19.25.E1> cK = _RF2(self, kp2, _1_0) cKE = k2 * cD eps = k2 / (sqrt(kp2) + _1_0)**2 else: # PYCHOK no cover cD = cK = cKE = INF cE = _1_0 eps = k2 else: # PYCHOK no cover cD = PI_4 cE = cK = PI_2 cKE = _0_0 # k2 * cD eps = EPS return _Complete(cD=cD, cE=cE, cK=cK, cKE=cKE, eps=eps) def sncndn(self, x): '''The Jacobi elliptic function. @arg x: The argument (C{float}). @return: An L{Elliptic3Tuple}C{(sn, cn, dn)} with C{*n(B{x}, k)}. @raise EllipticError: No convergence. ''' self._iteration = 0 # reset # Bulirsch's sncndn routine, p 89. if self.kp2: c, d, mn_ = self._sncndnBulirsch3 dn = _1_0 x *= (c * d) if d else c sn, cn = sincos2(x) if sn: a = cn / sn c *= a for m, n in mn_: a *= c c *= dn dn = (n + a) / (m + a) a = c / m sn = copysign0(_1_0 / hypot1(c), sn) # _signBit(sn) cn = c * sn if d and _signBit(self.kp2): # PYCHOK no cover cn, dn = dn, cn sn = sn / d # /= d chokes PyChecker else: sn = tanh(x) cn = dn = _1_0 / cosh(x) return Elliptic3Tuple(sn, cn, dn, iteration=self._iteration) @Property_RO def _sncndnBulirsch3(self): '''(INTERNAL) Get and cache Bulirsch' 3-tuple C{(c, d, mn_)}. ''' # Bulirsch's sncndn routine, p 89. d, mc = 0, self.kp2 if _signBit(mc): # PYCHOK no cover d = _1_0 - mc mc = neg(mc / d) d = sqrt(d) a, mn, t = _1_0, [], _TolJAC for i in range(1, _TRIPS): # GEOGRAPHICLIB_PANIC # This converges quadratically, max 6 trips mc = sqrt(mc) mn.append((a, mc)) c = (a + mc) * _0_5 if abs(a - mc) <= t: self._iteration += i # accumulate break mc *= a a = c t = a * _TolJAC else: # PYCHOK no cover raise _convergenceError(t, None, kp=self.kp, kp2=self.kp2) return c, d, tuple(reversed(mn)) # mn reversed! def _sncndnPhi(self, phi): '''(INTERNAL) Helper for C{.fEinv} and C{._fXf}. ''' sn, cn = sincos2(phi) return Elliptic3Tuple(sn, cn, self.fDelta(sn, cn)) @staticmethod def fRC(x, y): '''Degenerate symmetric integral of the first kind C{RC(x, y)}. @return: C{RC(x, y)}, equivalent to C{RF(x, y, y)}. @see: U{C{RC} definition<https://DLMF.NIST.gov/19.2.E17>} and U{Carlson<https://ArXiv.org/pdf/math/9409227.pdf>}. ''' return _RC(None, x, y) @staticmethod def fRD(x, y, z): '''Degenerate symmetric integral of the third kind C{RD(x, y, z)}. @return: C{RD(x, y, z)}, equivalent to C{RJ(x, y, z, z)}. @see: U{C{RD} definition<https://DLMF.NIST.gov/19.16.E5>} and U{Carlson<https://ArXiv.org/pdf/math/9409227.pdf>}. ''' return _RD(None, x, y, z) @staticmethod def fRF(x, y, *z): '''Symmetric or complete symmetric integral of the first kind C{RF(x, y, z)} respectively C{RF(x, y)}. @return: C{RF(x, y, z)} or C{RF(x, y)} for missing or zero B{C{z}}. @see: U{C{RF} definition<https://DLMF.NIST.gov/19.16.E1>} and U{Carlson<https://ArXiv.org/pdf/math/9409227.pdf>}. ''' return _RF3(None, x, y, *z) if z and z[0] else _RF2(None, x, y) @staticmethod def fRG(x, y, *z): '''Symmetric or complete symmetric integral of the second kind C{RG(x, y, z)} respectively C{RG(x, y)}. @return: C{RG(x, y, z)} or C{RG(x, y)} for missing or zero B{C{z}}. @see: U{C{RG} definition<https://DLMF.NIST.gov/19.16.E3>} and U{Carlson<https://ArXiv.org/pdf/math/9409227.pdf>}. ''' return _RG3(None, x, y, *z) if z and z[0] else (_RG2(None,x, y) * _0_5) @staticmethod def fRJ(x, y, z, p): '''Symmetric integral of the third kind C{RJ(x, y, z, p)}. @return: C{RJ(x, y, z, p)}. @see: U{C{RJ} definition<https://DLMF.NIST.gov/19.16.E2>} and U{Carlson<https://ArXiv.org/pdf/math/9409227.pdf>}. ''' return _RJ(None, x, y, z, p) class EllipticError(_ValueError): '''Elliptic integral, function, convergence or other L{Elliptic} issue. ''' pass class Elliptic3Tuple(_NamedTuple): '''3-Tuple C{(sn, cn, dn)} all C{scalar}. ''' _Names_ = ('sn', 'cn', 'dn') _Units_ = ( Scalar, Scalar, Scalar) def _callError(name, *args): # PYCHOK no cover '''(INTERNAL) Return an L{EllipticError}. ''' n = _DOT_(Elliptic.__name__, name) n = _SPACE_(_invokation_, n) return EllipticError(NN(n, repr(args))) # unstr def _convergenceError(tol, where, *args, **kwds): # PYCHOK no cover '''(INTERNAL) Return an L{EllipticError}. ''' n = Elliptic.__name__ if where: n = _DOT_(n, where.__name__) t = unstr(n, *args, **kwds) return EllipticError(_no_(_convergence_), tol, txt=t) def _horner(S, e1, E2, E3, E4, E5, *over): '''(INTERNAL) Horner form for C{_RD} and C{_RJ} below. ''' E22 = E2**2 # Polynomial is <https://DLMF.NIST.gov/19.36.E2> # (1 - 3*E2/14 + E3/6 + 9*E2**2/88 - 3*E4/22 - 9*E2*E3/52 # + 3*E5/26 - E2**3/16 + 3*E3**2/40 + 3*E2*E4/20 # + 45*E2**2*E3/272 - 9*(E3*E4+E2*E5)/68) # converted to Horner form ... e = e1 * 4084080 S *= e S += Fsum( E2 * -540540, 471240).fmul(E5) S += Fsum( E3 * -540540, E2 * 612612, -556920).fmul(E4) S += Fsum(E22 * 675675, E3 * 306306, E2 * -706860, 680680).fmul(E3) S += Fsum(E22 * -255255, E2 * 417690, -875160).fmul(E2) return S.fadd_(4084080).fover((e * over[0]) if over else e) def _iterations(inst, i): '''(INTERNAL) Aggregate iterations B{C{i}}. ''' if inst: inst._iteration += i def _Q(_Tol, A0, *ts): '''(INTERNAL) Helper for C{_RD}, C{_RF3} and C{_RJ}. ''' return max(abs(A0 - t) for t in ts) / _Tol def _RC(unused, x, y): '''(INTERNAL) Defined only for y != 0 and x >= 0. ''' d = x - y if d < 0: # catch _NaN # <https://DLMF.NIST.gov/19.2.E18> d = -d r = atan(sqrt(d / x)) if x > 0 else PI_2 elif d == _0_0: # XXX d < EPS0? or EPS02 or _EPSmin d, r = y, _1_0 elif y > 0: # <https://DLMF.NIST.gov/19.2.E19> r = asinh(sqrt(d / y)) # atanh(sqrt((x - y) / x)) elif y < 0: # <https://DLMF.NIST.gov/19.2.E20> r = asinh(sqrt(-x / y)) # atanh(sqrt(x / (x - y))) else: raise _callError(Elliptic.fRC.__name__, x, y) return r / sqrt(d) def _RD(inst, x, y, z, *over): '''(INTERNAL) Carlson, eqs 2.28 - 2.34. ''' A0 = Fsum(x, y, _3_0 * z).fover(_5_0) T = (A0, x, y, z) Q = _Q(_TolRF, *T) S = Fsum() m = 1 for i in range(_TRIPS): An = T[0] Am = An * m if Q < abs(Am): # max 7 trips _iterations(inst, i) break t = T[3] # z0...n T, s, r = _Tsr3(T) S += _1_0 / ((t + r) * s[2] * m) m *= 4 else: # PYCHOK no cover raise _convergenceError(Q, Elliptic.fRD, x, y, z) x, y = _xyz(A0, -Am, x, y) z = (x + y) / _3_0 z2 = z**2 xy = x * y S *= _3_0 return _horner(S, Am * sqrt(An), xy - _6_0 * z2, (xy * _3_0 - _8_0 * z2) * z, (xy - z2) * _3_0 * z2, xy * z2 * z, *over) def _3rd(a, b): '''(INTERNAL) Return _horner C{over} value. ''' return _3_0 / (a * b) def _RF2(inst, x, y): # 2-arg version, z=0 '''(INTERNAL) Carlson, eqs 2.36 - 2.38. ''' a, b = sqrt(x), sqrt(y) if a < b: a, b = b, a for i in range(_TRIPS): t = _TolRG0 * a if abs(a - b) <= t: # max 4 trips _iterations(inst, i) return (PI / (a + b)) b, a = sqrt(a * b), (a + b) * _0_5 else: # PYCHOK no cover raise _convergenceError(t, Elliptic.fRF, x, y) def _RF3(inst, x, y, z): # 3-arg version '''(INTERNAL) Carlson, eqs 2.2 - 2.7. ''' A0 = Fsum(x, y, z).fover(_3_0) T = (A0, x, y, z) Q = _Q(_TolRF, *T) m = 1 for i in range(_TRIPS): An = T[0] Am = An * m if Q < abs(Am): # max 6 trips _iterations(inst, i) break T, _, _ = _Tsr3(T) m *= 4 else: # PYCHOK no cover raise _convergenceError(Q, Elliptic.fRF, x, y, z) x, y = _xyz(A0, Am, x, y) z = neg(x + y) e2 = x * y - z**2 e3 = x * y * z e4 = e2**2 # Polynomial is <https://DLMF.NIST.gov/19.36.E1> # (1 - E2/10 + E3/14 + E2**2/24 - 3*E2*E3/44 # - 5*E2**3/208 + 3*E3**2/104 + E2**2*E3/16) # converted to Horner form ... S = Fsum(e4 * 15015, e3 * 6930, e2 * -16380, 17160).fmul(e3) S += Fsum(e4 * -5775, e2 * 10010, -24024).fmul(e2) return S.fadd_(240240).fover(sqrt(An) * 240240) def _RG2(inst, x, y): # 2-args and I{doubled} '''(INTERNAL) Carlson, eqs 2.36 - 2.39. ''' a, b = sqrt(x), sqrt(y) if a < b: a, b = b, a ab = a - b # abs(a - b) S = Fsum(_0_5 * (a + b)**2) m = -1 for i in range(_TRIPS): # max 4 trips t = _TolRG0 * a if ab <= t: _iterations(inst, i) return S.fover((a + b) / PI_2) a, b = ((a + b) * _0_5), sqrt(a * b) ab = abs(a - b) S += ab**2 * m m *= 2 else: # PYCHOK no cover raise _convergenceError(t, Elliptic.fRG, x, y) def _RG3(inst, x, y, z): # 3-arg version '''(INTERNAL) Never called with zero B{C{z}}, see C{.fRG}. ''' # if not z: # y, z = z, y rd = (x - z) * (z - y) # - (y - z) if rd: # Carlson, eq 1.7 rd = _RD(inst, x, y, z, _3_0 * z / rd) xyz = x * y if xyz: xyz = sqrt(xyz / z**3) return Fsum(_RF3(inst, x, y, z), rd, xyz).fover(_2_0 / z) def _RJ(inst, x, y, z, p, *over): '''(INTERNAL) Carlson, eqs 2.17 - 2.25. ''' def _xyzp(x, y, z, p): return (x + p) * (y + p) * (z + p) A0 = Fsum(x, y, z, _2_0 * p).fover(_5_0) T = (A0, x, y, z, p) Q = _Q(_TolRD, *T) S = Fsum() m = 1 Dn = neg(_xyzp(x, y, z, -p)) for i in range(_TRIPS): An = T[0] Am = An * m if Q < abs(Am): # max 7 trips _iterations(inst, i) break T, s, _ = _Tsr3(T) d = _xyzp(*s) if Dn: rc = _RC(inst, _1_0, Dn / d**2 + _1_0) Dn *= _1_64th else: rc = _1_0 # == _RC(None, _1_0, _1_0) S += rc / (d * m) m *= 4 else: # PYCHOK no cover raise _convergenceError(Q, Elliptic.fRJ, x, y, z, p) x, y, z = _xyz(A0, Am, x, y, z) xyz = x * y * z p = -Fsum(x, y, z).fover(_2_0) p2 = p**2 p3 = p**3 E2 = Fsum(x * y, x * z, y * z, -p2 * _3_0) E2p = E2 * p S *= _6_0 return _horner(S, Am * sqrt(An), E2, Fsum(p3 * _4_0, xyz, E2p * _2_0), Fsum(p3 * _3_0, E2p, xyz * _2_0).fmul(p), xyz * p2, *over) def _Tsr3(T): '''(INTERNAL) Helper for C{_RD}, C{_RF3} and C{_RJ}. ''' s = map2(sqrt, T[1:]) # sqrt(x), srqt(y), sqrt(z) [, sqrt(p)] r = fdot(s[:3], s[1], s[2], s[0]) # sqrt(x) * sqrt(y) + ... T = tuple((t + r) * _0_25 for t in T) # T[:] = ... return T, s, r def _xyz(A0, Am, *xyz): '''(INTERNAL) Rescale any C{xys}. ''' return tuple((A0 - x) / Am for x in xyz) # **) MIT License # # Copyright (C) 2016-2022 -- mrJean1 at Gmail -- All Rights Reserved. # # Permission is hereby granted, free of charge, to any person obtaining a # copy of this software and associated documentation files (the "Software"), # to deal in the Software without restriction, including without limitation # the rights to use, copy, modify, merge, publish, distribute, sublicense, # and/or sell copies of the Software, and to permit persons to whom the # Software is furnished to do so, subject to the following conditions: # # The above copyright notice and this permission notice shall be included # in all copies or substantial portions of the Software. # # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS # OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, # FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL # THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR # OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, # ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR # OTHER DEALINGS IN THE SOFTWARE.