| /* interpolation/akima.c |
| * |
| * Copyright (C) 1996, 1997, 1998, 1999, 2000 Gerard Jungman |
| * |
| * 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 2 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, write to the Free Software |
| * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. |
| */ |
| |
| /* Author: G. Jungman |
| */ |
| #include <config.h> |
| #include <stdlib.h> |
| #include <math.h> |
| #include <gsl/gsl_errno.h> |
| #include "integ_eval.h" |
| #include <gsl/gsl_interp.h> |
| |
| typedef struct |
| { |
| double * b; |
| double * c; |
| double * d; |
| double * _m; |
| } akima_state_t; |
| |
| |
| /* common creation */ |
| static void * |
| akima_alloc (size_t size) |
| { |
| akima_state_t *state = (akima_state_t *) malloc (sizeof (akima_state_t)); |
| |
| if (state == NULL) |
| { |
| GSL_ERROR_NULL("failed to allocate space for state", GSL_ENOMEM); |
| } |
| |
| state->b = (double *) malloc (size * sizeof (double)); |
| |
| if (state->b == NULL) |
| { |
| free (state); |
| GSL_ERROR_NULL("failed to allocate space for b", GSL_ENOMEM); |
| } |
| |
| state->c = (double *) malloc (size * sizeof (double)); |
| |
| if (state->c == NULL) |
| { |
| free (state->b); |
| free (state); |
| GSL_ERROR_NULL("failed to allocate space for c", GSL_ENOMEM); |
| } |
| |
| state->d = (double *) malloc (size * sizeof (double)); |
| |
| if (state->d == NULL) |
| { |
| free (state->c); |
| free (state->b); |
| free (state); |
| GSL_ERROR_NULL("failed to allocate space for d", GSL_ENOMEM); |
| } |
| |
| state->_m = (double *) malloc ((size + 4) * sizeof (double)); |
| |
| if (state->_m == NULL) |
| { |
| free (state->d); |
| free (state->c); |
| free (state->b); |
| free (state); |
| GSL_ERROR_NULL("failed to allocate space for _m", GSL_ENOMEM); |
| } |
| |
| return state; |
| } |
| |
| |
| /* common calculation */ |
| static void |
| akima_calc (const double x_array[], double b[], double c[], double d[], size_t size, double m[]) |
| { |
| size_t i; |
| |
| for (i = 0; i < (size - 1); i++) |
| { |
| const double NE = fabs (m[i + 1] - m[i]) + fabs (m[i - 1] - m[i - 2]); |
| if (NE == 0.0) |
| { |
| b[i] = m[i]; |
| c[i] = 0.0; |
| d[i] = 0.0; |
| } |
| else |
| { |
| const double h_i = x_array[i + 1] - x_array[i]; |
| const double NE_next = fabs (m[i + 2] - m[i + 1]) + fabs (m[i] - m[i - 1]); |
| const double alpha_i = fabs (m[i - 1] - m[i - 2]) / NE; |
| double alpha_ip1; |
| double tL_ip1; |
| if (NE_next == 0.0) |
| { |
| tL_ip1 = m[i]; |
| } |
| else |
| { |
| alpha_ip1 = fabs (m[i] - m[i - 1]) / NE_next; |
| tL_ip1 = (1.0 - alpha_ip1) * m[i] + alpha_ip1 * m[i + 1]; |
| } |
| b[i] = (1.0 - alpha_i) * m[i - 1] + alpha_i * m[i]; |
| c[i] = (3.0 * m[i] - 2.0 * b[i] - tL_ip1) / h_i; |
| d[i] = (b[i] + tL_ip1 - 2.0 * m[i]) / (h_i * h_i); |
| } |
| } |
| } |
| |
| |
| static int |
| akima_init (void * vstate, const double x_array[], const double y_array[], |
| size_t size) |
| { |
| akima_state_t *state = (akima_state_t *) vstate; |
| |
| double * m = state->_m + 2; /* offset so we can address the -1,-2 |
| components */ |
| |
| size_t i; |
| for (i = 0; i <= size - 2; i++) |
| { |
| m[i] = (y_array[i + 1] - y_array[i]) / (x_array[i + 1] - x_array[i]); |
| } |
| |
| /* non-periodic boundary conditions */ |
| m[-2] = 3.0 * m[0] - 2.0 * m[1]; |
| m[-1] = 2.0 * m[0] - m[1]; |
| m[size - 1] = 2.0 * m[size - 2] - m[size - 3]; |
| m[size] = 3.0 * m[size - 2] - 2.0 * m[size - 3]; |
| |
| akima_calc (x_array, state->b, state->c, state->d, size, m); |
| |
| return GSL_SUCCESS; |
| } |
| |
| |
| static int |
| akima_init_periodic (void * vstate, |
| const double x_array[], |
| const double y_array[], |
| size_t size) |
| { |
| akima_state_t *state = (akima_state_t *) vstate; |
| |
| double * m = state->_m + 2; /* offset so we can address the -1,-2 |
| components */ |
| |
| size_t i; |
| for (i = 0; i <= size - 2; i++) |
| { |
| m[i] = (y_array[i + 1] - y_array[i]) / (x_array[i + 1] - x_array[i]); |
| } |
| |
| /* periodic boundary conditions */ |
| m[-2] = m[size - 1 - 2]; |
| m[-1] = m[size - 1 - 1]; |
| m[size - 1] = m[0]; |
| m[size] = m[1]; |
| |
| akima_calc (x_array, state->b, state->c, state->d, size, m); |
| |
| return GSL_SUCCESS; |
| } |
| |
| static void |
| akima_free (void * vstate) |
| { |
| akima_state_t *state = (akima_state_t *) vstate; |
| |
| free (state->b); |
| free (state->c); |
| free (state->d); |
| free (state->_m); |
| free (state); |
| } |
| |
| |
| static |
| int |
| akima_eval (const void * vstate, |
| const double x_array[], const double y_array[], size_t size, |
| double x, |
| gsl_interp_accel * a, |
| double *y) |
| { |
| const akima_state_t *state = (const akima_state_t *) vstate; |
| |
| size_t index; |
| |
| if (a != 0) |
| { |
| index = gsl_interp_accel_find (a, x_array, size, x); |
| } |
| else |
| { |
| index = gsl_interp_bsearch (x_array, x, 0, size - 1); |
| } |
| |
| /* evaluate */ |
| { |
| const double x_lo = x_array[index]; |
| const double delx = x - x_lo; |
| const double b = state->b[index]; |
| const double c = state->c[index]; |
| const double d = state->d[index]; |
| *y = y_array[index] + delx * (b + delx * (c + d * delx)); |
| return GSL_SUCCESS; |
| } |
| } |
| |
| |
| static int |
| akima_eval_deriv (const void * vstate, |
| const double x_array[], const double y_array[], size_t size, |
| double x, |
| gsl_interp_accel * a, |
| double *dydx) |
| { |
| const akima_state_t *state = (const akima_state_t *) vstate; |
| |
| size_t index; |
| |
| DISCARD_POINTER(y_array); /* prevent warning about unused parameter */ |
| |
| if (a != 0) |
| { |
| index = gsl_interp_accel_find (a, x_array, size, x); |
| } |
| else |
| { |
| index = gsl_interp_bsearch (x_array, x, 0, size - 1); |
| } |
| |
| /* evaluate */ |
| { |
| double x_lo = x_array[index]; |
| double delx = x - x_lo; |
| double b = state->b[index]; |
| double c = state->c[index]; |
| double d = state->d[index]; |
| *dydx = b + delx * (2.0 * c + 3.0 * d * delx); |
| return GSL_SUCCESS; |
| } |
| } |
| |
| |
| static |
| int |
| akima_eval_deriv2 (const void * vstate, |
| const double x_array[], const double y_array[], size_t size, |
| double x, |
| gsl_interp_accel * a, |
| double *y_pp) |
| { |
| const akima_state_t *state = (const akima_state_t *) vstate; |
| |
| size_t index; |
| |
| DISCARD_POINTER(y_array); /* prevent warning about unused parameter */ |
| |
| if (a != 0) |
| { |
| index = gsl_interp_accel_find (a, x_array, size, x); |
| } |
| else |
| { |
| index = gsl_interp_bsearch (x_array, x, 0, size - 1); |
| } |
| |
| /* evaluate */ |
| { |
| const double x_lo = x_array[index]; |
| const double delx = x - x_lo; |
| const double c = state->c[index]; |
| const double d = state->d[index]; |
| *y_pp = 2.0 * c + 6.0 * d * delx; |
| return GSL_SUCCESS; |
| } |
| } |
| |
| |
| static |
| int |
| akima_eval_integ (const void * vstate, |
| const double x_array[], const double y_array[], size_t size, |
| gsl_interp_accel * acc, |
| double a, double b, |
| double * result) |
| { |
| const akima_state_t *state = (const akima_state_t *) vstate; |
| |
| size_t i, index_a, index_b; |
| |
| if (acc != 0) |
| { |
| index_a = gsl_interp_accel_find (acc, x_array, size, a); |
| index_b = gsl_interp_accel_find (acc, x_array, size, b); |
| } |
| else |
| { |
| index_a = gsl_interp_bsearch (x_array, a, 0, size - 1); |
| index_b = gsl_interp_bsearch (x_array, b, 0, size - 1); |
| } |
| |
| *result = 0.0; |
| |
| /* interior intervals */ |
| |
| for(i=index_a; i<=index_b; i++) { |
| const double x_hi = x_array[i + 1]; |
| const double x_lo = x_array[i]; |
| const double y_lo = y_array[i]; |
| const double dx = x_hi - x_lo; |
| if(dx != 0.0) { |
| |
| if (i == index_a || i == index_b) |
| { |
| double x1 = (i == index_a) ? a : x_lo; |
| double x2 = (i == index_b) ? b : x_hi; |
| *result += integ_eval (y_lo, state->b[i], state->c[i], state->d[i], |
| x_lo, x1, x2); |
| } |
| else |
| { |
| *result += dx * (y_lo |
| + dx*(0.5*state->b[i] |
| + dx*(state->c[i]/3.0 |
| + 0.25*state->d[i]*dx))); |
| } |
| } |
| else { |
| *result = 0.0; |
| return GSL_FAILURE; |
| } |
| } |
| |
| return GSL_SUCCESS; |
| } |
| |
| |
| static const gsl_interp_type akima_type = |
| { |
| "akima", |
| 5, |
| &akima_alloc, |
| &akima_init, |
| &akima_eval, |
| &akima_eval_deriv, |
| &akima_eval_deriv2, |
| &akima_eval_integ, |
| &akima_free |
| }; |
| |
| const gsl_interp_type * gsl_interp_akima = &akima_type; |
| |
| static const gsl_interp_type akima_periodic_type = |
| { |
| "akima-periodic", |
| 5, |
| &akima_alloc, |
| &akima_init_periodic, |
| &akima_eval, |
| &akima_eval_deriv, |
| &akima_eval_deriv2, |
| &akima_eval_integ, |
| &akima_free |
| }; |
| |
| const gsl_interp_type * gsl_interp_akima_periodic = &akima_periodic_type; |