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/*
* Copyright 2017 Anton Khirnov <anton@khirnov.net>
*
* 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 <http://www.gnu.org/licenses/>.
*/
#ifndef TEUKOLSKY_DATA_H
#define TEUKOLSKY_DATA_H
#include <stdarg.h>
#include <stddef.h>
#include <stdint.h>
/**
* API usage:
*
* First, allocate the solver context with td_context_alloc(). All interaction
* with the solver is done through this context.
*
* Fill any fields in the context that are described as settable by the caller.
* Call td_solve() to solve the equation determined by the option values.
*
* The metric/extrinsic curvature can be evaluated with td_eval_metric()/td_eval_curv().
*
* Finally, free the solver context with td_context_free().
*/
/**
* Identifies the specific initial data family to use.
*/
enum TDFamily {
/**
* Time-antisymmetric initial data with a cubic radial term multiplied by an
* exponential and a quadrupole angular term.
* Similar to that used in Abrahams&Evans PhysRevD v49,n8 (1994).
* Conformally flat spatial metric.
* r / x x 3 \ / x 2 \
* K = a | 3 --- - 2 (---) | * exp| - (---) | sin(2θ)
* θ \ L L / \ L /
*/
TD_FAMILY_TIME_ANTISYM_CUBIC = 0,
/**
* Time-antisymmetric initial data with a linear radial term multiplied by
* an exponential and a quadrupole angular term.
* Conformally flat spatial metric.
* r x / x 2 \
* K = a --- exp| - (---) | sin(2θ)
* θ L \ L /
*/
TD_FAMILY_TIME_ANTISYM_LINEAR,
};
typedef struct TDContext {
/**
* Solver internals, not to be accessed by the caller
*/
void *priv;
/********************************
* options, set by the caller *
********************************/
/**
* A callback that will be used to print diagnostic messages.
*
* Defaults to fprintf(stderr, ...)
*/
void (*log_callback)(const struct TDContext *td, int level,
const char *fmt, va_list);
/**
* Arbitrary user data, e.g. to be used by the log callback.
*/
void *opaque;
/********************************
* initial data parameters *
********************************/
/**
* The amplitude in the I function.
* Defaults to 1.
*/
double amplitude;
/********************************
* solver options *
********************************/
/**
* The number of basis functions in each direction.
* [0] - radial, [1] - angular
*/
unsigned int nb_coeffs[2];
/**
* The scaling factor used in the basis functions.
* [0] - radial, [1] - angular
*/
double basis_scale_factor[2];
/**
* Maximum number of Newton iterations.
*/
unsigned int max_iter;
/**
* Absolute tolerance. The solver is deemed to have converged
* after maximum difference between iterations is below this bound.
*/
double atol;
/**
* Number of threads to use for parallelization. Set to 0 to automatically
* detect according to the number of CPU cores.
*/
unsigned int nb_threads;
double *coeffs[3];
unsigned int solution_branch;
enum TDFamily family;
} TDContext;
/**
* Allocate and initialize the solver.
*/
TDContext *td_context_alloc(void);
/**
* Free the solver and everything associated with it.
*/
void td_context_free(TDContext **td);
/**
* Solve the equation for the conformal factor ψ and export the expansion coefficients in the
* context.
*
* @return >= 0 on success, a negative error code on failure
*/
int td_solve(TDContext *td, double *coeffs_init[3]);
/**
* Evaluate the conformal factor ψ at the specified points in spherical
* coordinates { r, θ, φ } (since the spacetime is axially symmetric, φ is
* disregarded).
*
* @param td the solver context
* @param nb_coords number of elements in the r and theta arrays
* @param r values of r coordinates
* @param theta values of θ coordinates
* @param diff_order order of the derivatives of the metric to evaluate. The
* first element specifies the derivative wrt r, the second
* wrt θ. I.e. diff_order[i] = { 0, 0 } evaluates ψ itself,
* diff_order = { 0, 1 } evaluates ∂ψ/∂θ etc.
* @param out a nb_coords-sized array into which the values of the ψ will be
* written. out[i] is the value of ψ at the spacetime point { r[i], θ[i], 0 }
*
* @return >= 0 on success, a negative error code on failure.
*/
int td_eval_psi(const TDContext *td,
size_t nb_coords, const double *r, const double *theta,
const unsigned int diff_order[2],
double *out);
/**
* Same as td_eval_psi(), except K_{r}^r ('rr' component of the mixed-index
* extrinsic curvature tensor) is evaluated.
*/
int td_eval_krr(const TDContext *td,
size_t nb_coords, const double *r, const double *theta,
const unsigned int diff_order[2],
double *out);
/**
* Same as td_eval_psi(), except K_{φ}^φ ('φφ' component of the mixed-index
* extrinsic curvature tensor) is evaluated.
*/
int td_eval_kpp(const TDContext *td,
size_t nb_coords, const double *r, const double *theta,
const unsigned int diff_order[2],
double *out);
/**
* Same as td_eval_psi(), except K_{r}^θ ('rθ' component of the mixed-index
* extrinsic curvature tensor) is evaluated.
*/
int td_eval_krt(const TDContext *td,
size_t nb_coords, const double *r, const double *theta,
const unsigned int diff_order[2],
double *out);
/**
* Compute the values of lapse that would make the spacetime slice maximal.
* Parameters are the same as for td_eval_psi().
*/
int td_eval_lapse(const TDContext *td,
size_t nb_coords, const double *r, const double *theta,
const unsigned int diff_order[2],
double *out);
#endif /* TEUKOLSKY_DATA_H */
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