Vehicle-cpp/hkpc/software/scipy/integrate/_ivp/tests/test_rk.py

import pytest
from numpy.testing import assert_allclose, assert_
import numpy as np
from scipy.integrate import RK23, RK45, DOP853
from scipy.integrate._ivp import dop853_coefficients


@pytest.mark.parametrize("solver", [RK23, RK45, DOP853])
def test_coefficient_properties(solver):
    assert_allclose(np.sum(solver.B), 1, rtol=1e-15)
    assert_allclose(np.sum(solver.A, axis=1), solver.C, rtol=1e-14)


def test_coefficient_properties_dop853():
    assert_allclose(np.sum(dop853_coefficients.B), 1, rtol=1e-15)
    assert_allclose(np.sum(dop853_coefficients.A, axis=1),
                    dop853_coefficients.C,
                    rtol=1e-14)


@pytest.mark.parametrize("solver_class", [RK23, RK45, DOP853])
def test_error_estimation(solver_class):
    step = 0.2
    solver = solver_class(lambda t, y: y, 0, [1], 1, first_step=step)
    solver.step()
    error_estimate = solver._estimate_error(solver.K, step)
    error = solver.y - np.exp([step])
    assert_(np.abs(error) < np.abs(error_estimate))


@pytest.mark.parametrize("solver_class", [RK23, RK45, DOP853])
def test_error_estimation_complex(solver_class):
    h = 0.2
    solver = solver_class(lambda t, y: 1j * y, 0, [1j], 1, first_step=h)
    solver.step()
    err_norm = solver._estimate_error_norm(solver.K, h, scale=[1])
    assert np.isrealobj(err_norm)