ode_common.c

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#include "internal.h"
#include "lmmc/ode.h"
 
const char* lmmc_ode_failure_string(lmmc_ode_failure_t reason) {
    switch (reason) {
        case LMMC_ODE_FAILURE_NONE: {
            return "none";
        }
        case LMMC_ODE_FAILURE_INVALID_DIMENSION: {
            return "invalid dimension";
        }
        case LMMC_ODE_FAILURE_INVALID_STEP: {
            return "invalid step";
        }
        case LMMC_ODE_FAILURE_MAX_STEPS: {
            return "max steps reached";
        }
        case LMMC_ODE_FAILURE_NUMERICAL_ISSUE: {
            return "numerical issue";
        }
        case LMMC_ODE_FAILURE_RHS_EVAL_FAILED: {
            return "rhs evaluation failed";
        }
        case LMMC_ODE_FAILURE_TOLERANCE_INCONSISTENT: {
            return "tolerance inconsistent";
        }
        default: {
            return "unknown";
        }
    }
}
 
static size_t ode_default_max_steps(size_t problem_dim) {
    if (problem_dim > ((size_t)-1) / 10000) {
        return 100000;
    }
    size_t max_steps = problem_dim * 10000;
    if (max_steps < 1000) {
        max_steps = 1000;
    }
    return max_steps;
}
 
lmmc_status_t lmmc_ode_default_config(
    lmmc_real_t t_start,
    lmmc_real_t t_end,
    size_t problem_dim,
    lmmc_ode_config_t* out_cfg
) {
    lmmc_real_t span = 0.0;
    lmmc_real_t initial_step = 0.0;
    lmmc_real_t min_step = 0.0;
    lmmc_real_t max_step = 0.0;
    size_t max_steps = 0;
    lmmc_real_t hundred = 100.0;
    lmmc_real_t ten = 10.0;
    lmmc_real_t span_factor = 1e-10;
    lmmc_real_t step_factor = 1e-6;
    lmmc_real_t tenth = 0.1;
 
    if (out_cfg == NULL || problem_dim == 0 || !lmmc_is_finite(&t_start) ||
        !lmmc_is_finite(&t_end) || !(t_end > t_start)) {
        return LMMC_STATUS_INVALID_ARGUMENT;
    }
 
    LMMC_REAL_SUB(&span, &t_end, &t_start);
    LMMC_REAL_DIV(&initial_step, &span, &hundred);
    if (!lmmc_is_finite(&initial_step) || initial_step <= 0.0) {
        LMMC_REAL_SET_D(&initial_step, 1e-3);
    }
 
    LMMC_REAL_MUL(&min_step, &span, &span_factor);
    if (!lmmc_is_finite(&min_step) || min_step <= 0.0) {
        LMMC_REAL_MUL(&min_step, &initial_step, &step_factor);
    }
    if (min_step > initial_step) {
        LMMC_REAL_MUL(&min_step, &initial_step, &tenth);
    }
 
    LMMC_REAL_DIV(&max_step, &span, &ten);
    if (!lmmc_is_finite(&max_step) || max_step <= 0.0) {
        LMMC_REAL_SET(&max_step, &initial_step);
    }
    if (max_step < initial_step) {
        LMMC_REAL_SET(&max_step, &initial_step);
    }
 
    max_steps = ode_default_max_steps(problem_dim);
 
    out_cfg->initial_step = initial_step;
    out_cfg->min_step = min_step;
    out_cfg->max_step = max_step;
    out_cfg->abs_tol = LMMC_DEFAULT_ABS_TOL;
    out_cfg->rel_tol = LMMC_DEFAULT_REL_TOL;
    out_cfg->max_steps = max_steps;
    out_cfg->adaptive_step_beta = 0.9;
    out_cfg->diagnostics = (lmmc_diagnostic_sink_t){0};
    out_cfg->jacobian = NULL;
    out_cfg->time_derivative = NULL;
    return LMMC_STATUS_OK;
}