# MeepMeep: fast orbit calculations for exoplanet modelling
# Copyright (C) 2022-2026 Hannu Parviainen
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <https://www.gnu.org/licenses/>.
"""Single-expansion-point 3D line-of-sight (z) velocity evaluators with parameter derivatives."""
from numba import njit, prange, types
from numba.extending import overload
from numpy import floor, zeros, ndarray
from numpy.typing import NDArray
from ._common import _is_1d_array
@njit(fastmath=True, inline='always')
def _zvel_cd_w(time, c, dc, dvz):
"""Write-into kernel shared by the scalar and vector evaluators.
Writes the seven-parameter gradient into the caller-provided ``(7,)``
buffer ``dvz`` and returns the z velocity, so the hot vector loops
reuse preallocated rows instead of allocating per sample.
"""
vz = c[2, 1] + time * (2.0 * c[2, 2] + time * (3.0 * c[2, 3] + time * 4.0 * c[2, 4]))
for k in range(7):
dvz[k] = dc[k, 2, 1] + time * (2.0 * dc[k, 2, 2] + time * (3.0 * dc[k, 2, 3] + time * 4.0 * dc[k, 2, 4]))
return vz
@njit(fastmath=True)
def _zvel_cd_s(time, c, dc):
"""Scalar kernel for :func:`zvel_cd`. See that function for documentation."""
dvz = zeros(7)
vz = _zvel_cd_w(time, c, dc, dvz)
return vz, dvz
def _zvel_cd_v_body(time, c, dc):
"""Vector-kernel body for :func:`zvel_cd`; see that function for documentation.
Compiled twice: ``zvel_cd_v`` is the serial kernel (``prange`` compiles
as a plain ``range`` without ``parallel=True``) and ``zvel_cd_vp`` the
parallel twin. The loop writes only into per-sample output elements,
so no per-thread scratch is needed.
"""
n = time.size
vz = zeros(n)
dvz = zeros((n, 7))
for j in prange(n):
vz[j] = _zvel_cd_w(time[j], c, dc, dvz[j])
return vz, dvz
zvel_cd_v = njit(fastmath=True)(_zvel_cd_v_body)
zvel_cd_vp = njit(fastmath=True, parallel=True)(_zvel_cd_v_body)
[docs]
def zvel_cd(time: float | NDArray, c: NDArray, dc: NDArray):
"""
Evaluate the line-of-sight velocity and its parameter derivatives at an expansion-point-centered time.
Centered companion to `velocity.zvel_c` that additionally
returns the partial derivatives of the line-of-sight velocity
with respect to each of the seven orbital parameters. Only the
z-direction polynomials are evaluated; the x and y rows of `c`
and `dc` are not read.
Accepts a scalar time or a 1-D array of times and dispatches to the
appropriate kernel at compile time (inside ``@njit``) or at call time
(pure Python), mirroring the value-only `velocity.zvel_c`.
Parameters
----------
time : float or ndarray
Time(s) relative to the Taylor series expansion point.
c : NDArray
A (3, 5) coefficient matrix produced by `solve3d`. Only row 2
(the z-direction coefficients) is read.
dc : NDArray
A (7, 3, 5) parameter-derivative tensor produced by
`solve3d_d`, with the leading axis ordered as
`(tc, p, a, i, e, w, lan)`. Only the slice `dc[:, 2, :]` is read.
Returns
-------
vz : float or ndarray
Line-of-sight z velocity in stellar radii per unit time.
Positive values indicate motion toward the observer. Shape (N,)
for an array `time`.
dvz : NDArray
Partial derivatives of `vz` with respect to `(tc, p, a, i, e, w, lan)`.
Shape (7,) for a scalar `time`, (N, 7) for an array `time`.
"""
if isinstance(time, ndarray):
return zvel_cd_v(time, c, dc)
return _zvel_cd_s(time, c, dc)
@overload(zvel_cd, jit_options={'fastmath': True})
def _zvel_cd_overload(time, c, dc):
if _is_1d_array(time):
def impl(time, c, dc):
return zvel_cd_v(time, c, dc)
return impl
if isinstance(time, types.Float):
def impl(time, c, dc):
return _zvel_cd_s(time, c, dc)
return impl
return None
@njit(fastmath=True)
def _zvel_d_s(time, tc, p, c, dc, te):
"""Scalar kernel for :func:`zvel_d`. See that function for documentation."""
epoch = floor((time - tc - te + 0.5 * p) / p)
return _zvel_cd_s(time - (tc + te + epoch * p), c, dc)
def _zvel_d_v_body(time, tc, p, c, dc, te):
"""Vector-kernel body for :func:`zvel_d`; see that function for documentation.
Compiled twice: ``zvel_d_v`` is the serial kernel (``prange`` compiles
as a plain ``range`` without ``parallel=True``) and ``zvel_d_vp`` the
parallel twin. The loop writes only into per-sample output elements,
so no per-thread scratch is needed.
"""
n = time.size
vz = zeros(n)
dvz = zeros((n, 7))
for j in prange(n):
epoch = floor((time[j] - tc - te + 0.5 * p) / p)
vz[j] = _zvel_cd_w(time[j] - (tc + te + epoch * p), c, dc, dvz[j])
return vz, dvz
zvel_d_v = njit(fastmath=True)(_zvel_d_v_body)
zvel_d_vp = njit(fastmath=True, parallel=True)(_zvel_d_v_body)
[docs]
def zvel_d(time: float | NDArray, tc: float, p: float, c: NDArray, dc: NDArray, te: float = 0.0):
"""
Evaluate the line-of-sight velocity and its parameter derivatives at an absolute time.
Direct counterpart of `zvel_cd`: epoch-folds the absolute time
`time` around the expansion point and delegates to
`zvel_cd`.
Accepts a scalar time or a 1-D array of times and dispatches to the
appropriate kernel at compile time (inside ``@njit``) or at call time
(pure Python), mirroring the value-only `velocity.zvel`.
Parameters
----------
time : float or ndarray
Absolute observation time(s) in the same units as `tc` and `p`.
tc : float
Transit-centre time (time of inferior conjunction), on the same
time axis as `time`.
p : float
Orbital period, used for epoch folding.
c : NDArray
A (3, 5) coefficient matrix produced by `solve3d`. Only row 2
is read.
dc : NDArray
A (7, 3, 5) parameter-derivative tensor produced by
`solve3d_d`. Only the slice `dc[:, 2, :]` is read.
te : float, optional
Expansion-point offset from the transit centre [days] - the same value that
was passed to `solve3d_d`. Defaults to 0.0, the expansion point at the
transit centre.
Returns
-------
vz : float or ndarray
Line-of-sight z velocity in stellar radii per unit time.
Positive values indicate motion toward the observer. Shape (N,)
for an array `time`.
dvz : NDArray
Partial derivatives of `vz` with respect to `(tc, p, a, i, e, w, lan)`.
Shape (7,) for a scalar `time`, (N, 7) for an array `time`.
"""
if isinstance(time, ndarray):
return zvel_d_v(time, tc, p, c, dc, te)
return _zvel_d_s(time, tc, p, c, dc, te)
@overload(zvel_d, jit_options={'fastmath': True})
def _zvel_d_overload(time, tc, p, c, dc, te=0.0):
if _is_1d_array(time):
def impl(time, tc, p, c, dc, te=0.0):
return zvel_d_v(time, tc, p, c, dc, te)
return impl
if isinstance(time, types.Float):
def impl(time, tc, p, c, dc, te=0.0):
return _zvel_d_s(time, tc, p, c, dc, te)
return impl
return None