def test_chkrebtii(self):
# LHS vector of ODE
w_mat = np.array([[0.0, 0.0, 1.0]])
# These parameters define the order of the ODE and the CAR(p) process
n_deriv = [2]
n_deriv_prior = [4]
# it is assumed that the solution is sought on the interval [tmin, tmax].
n_eval = 100
tmin = 0
tmax = 10
# IBM process scale factor
sigma = [.5]
# Initial value, x0, for the IVP
x0 = np.array([-1., 0., 1.])
x0_state = zero_pad(x0, n_deriv, n_deriv_prior)
W = zero_pad(w_mat, n_deriv, n_deriv_prior)
# Get parameters needed to run the solver
dt = (tmax - tmin) / n_eval
# All necessary parameters are in kinit, namely, T, c, R, W
kinit = ibm_init(dt, n_deriv_prior, sigma)
z_state = rand_mat(n_eval, sum(n_deriv_prior))
# Get Cython solution
kode_cy = KalmanODE_cy(W, tmin, tmax, n_eval, chkrebtii_kalman,
**kinit)
kode_cy.z_state = z_state
# Run the solver to get an approximation
ksim_cy = kode_cy.solve_sim(x0_state)
# Get Eigen solution
kode_ei = KalmanODE_ei(W, tmin, tmax, n_eval, chkrebtii_kalman,
**kinit)
kode_ei.z_state = z_state
ksim_ei = kode_ei.solve_sim(x0_state)
# Get Numba solution
kode_nb = KalmanODE_nb(W, tmin, tmax, n_eval, chkrebtii_kalman_nb,
**kinit)
kode_nb.z_state = z_state
ksim_nb = kode_nb.solve_sim(x0_state, W, None)
# Get Python solution
kalmanode_py = KalmanODE_py(W, tmin, tmax, n_eval, chkrebtii_kalman,
**kinit) # Initialize the class
kalmanode_py.z_state = z_state
ksim_py = kalmanode_py.solve_sim(x0_state, W)
self.assertLessEqual(rel_err(ksim_cy[:, 0], ksim_py[:, 0]), 0.001)
self.assertLessEqual(rel_err(ksim_cy[1:, 1], ksim_py[1:, 1]), 0.001)
self.assertLessEqual(rel_err(ksim_cy[:, 0], ksim_ei[:, 0]), 0.001)
self.assertLessEqual(rel_err(ksim_cy[1:, 1], ksim_ei[1:, 1]), 0.001)
self.assertLessEqual(rel_err(ksim_cy[:, 0], ksim_nb[:, 0]), 0.001)
self.assertLessEqual(rel_err(ksim_cy[1:, 1], ksim_nb[1:, 1]), 0.001)
def chkrebtii_example():
r"Produces the graph in Figure 1 of the paper."
# LHS vector of ODE
# 2. Define the IVP
W = np.array([[0.0, 0.0, 1.0]]) # LHS vector of ODE
x0 = np.array([-1., 0., 1.]) # initial value for the IVP
# Time interval on which a solution is sought.
tmin = 0
tmax = 10
# 3. Define the prior process
#
# (Perhaps best to describe this in text, not code comments)
#
# We're going to use a solution prior that has one more derivative than as specified in the IVP.
# To do this, we'll pad the original IVP with zeros, for which we have the convenience function
# zero_pad().
n_deriv = [2] # number of derivatives in IVP
n_deriv_prior = [4] # number of derivatives in IBM prior
# zero padding
W_pad = zero_pad(W, n_deriv, n_deriv_prior)
x0_pad = zero_pad(x0, n_deriv, n_deriv_prior)
# IBM process scale factor
sigma = [.5]
# 4. Instantiate the ODE solver object.
n_points = 80 # number of steps in which to discretize the time interval.
dt = (tmax - tmin) / n_points # step size
# generate the Kalman parameters corresponding to the prior
prior = ibm_init(dt, n_deriv_prior, sigma)
# instantiate the ODE solver
ode = KalmanODE(W=W_pad,
tmin=tmin,
tmax=tmax,
n_eval=n_points,
fun=ode_fun,
**prior)
# 5. Evaluate the ODE solution
# deterministic output: posterior mean
mut, Sigmat = ode.solve_mv(x0=x0_pad)
# probabilistic output: draw from posterior
xt = ode.solve_sim(x0=x0_pad)
# Produces the graph in Figure 1
draws = 100
readme_graph(ode_fun, n_deriv, n_deriv_prior, tmin, tmax, W, x0, draws)
return
def readme_kalman_draw(fun, n_deriv, n_deriv_prior, n_eval, tmin, tmax, sigma,
w_mat, init, draws):
dt = (tmax - tmin) / n_eval
X = np.zeros((draws, n_eval + 1, sum(n_deriv_prior)))
W = zero_pad(w_mat, n_deriv, n_deriv_prior)
x0_state = zero_pad(init, n_deriv, n_deriv_prior)
prior = ibm_init(dt, n_deriv_prior, sigma)
kalmanode = KalmanODE(W, tmin, tmax, n_eval, fun, **prior)
for i in range(draws):
X[i] = kalmanode.solve_sim(x0_state, W)
del kalmanode.z_state
return X
def test_chkrebtii(self):
# LHS vector of ODE
w_mat = np.array([[0.0, 0.0, 1.0]])
# These parameters define the order of the ODE and the CAR(p) process
n_deriv = [2]
n_deriv_prior = [4]
# it is assumed that the solution is sought on the interval [tmin, tmax].
n_eval = 300
tmin = 0
tmax = 10
# IBM process scale factor
sigma = [.5]
# Initial value, x0, for the IVP
x0 = np.array([-1., 0., 1.])
x0_state = zero_pad(x0, n_deriv, n_deriv_prior)
W = zero_pad(w_mat, n_deriv, n_deriv_prior)
# Get parameters needed to run the solver
dt = (tmax - tmin) / n_eval
# All necessary parameters are in kinit, namely, T, c, R, W
kinit = ibm_init(dt, n_deriv_prior, sigma)
# Initialize the Kalman class
kalmanode = KalmanODE(W, tmin, tmax, n_eval, chkrebtii_kalman, **kinit)
# Run the solver to get an approximation
kalman_sim = kalmanode.solve_sim(x0_state)
# Get deterministic solution from odeint
tseq = np.linspace(tmin, tmax, n_eval + 1)
detode = integrate.odeint(chkrebtii_odeint, [-1, 0], tseq)
self.assertLessEqual(rel_err(kalman_sim[:, 0], detode[:, 0]), 10.0)
self.assertLessEqual(rel_err(kalman_sim[1:, 1], detode[1:, 1]), 10.0)
def mseir_example():
"Perform parameter inference using the MSEIR function."
# These parameters define the order of the ODE and the CAR(p) process
n_deriv = [1] * 5 # Total state
n_deriv_prior = [3] * 5
state_ind = [0, 3, 6, 9, 12] # Index of 0th derivative of each state
# it is assumed that the solution is sought on the interval [tmin, tmax].
tmin = 0
tmax = 40
# The rest of the parameters can be tuned according to ODE
# For this problem, we will use
n_var = 5
sigma = [.1] * n_var
# Initial value, x0, for the IVP
theta_true = (1.1, 0.7, 0.4, 0.005, 0.02, 0.03) # True theta
x0 = np.array([1000, 100, 50, 3, 3])
v0 = mseir(x0, 0, theta_true)
X0 = np.ravel([x0, v0], 'F')
# W matrix: dimension is n_eq x sum(n_deriv)
W_mat = np.zeros((len(n_deriv), sum(n_deriv) + len(n_deriv)))
for i in range(len(n_deriv)):
W_mat[i, sum(n_deriv[:i]) + i + 1] = 1
W = zero_pad(W_mat, n_deriv, n_deriv_prior)
# logprior parameters
n_theta = len(theta_true)
phi_sd = np.ones(n_theta)
# Observation noise
gamma = 0.2
# Number of samples to draw from posterior
n_samples = 100000
# Initialize inference class and simulate observed data
inf = inference(state_ind, tmin, tmax, mseir)
Y_t = inf.simulate(mseir, x0, theta_true, gamma)
# Parameter inference using Euler's approximation
hlst = np.array([0.1, 0.05, 0.02, 0.01, 0.005])
theta_euler = np.zeros((len(hlst), n_samples, n_theta))
for i in range(len(hlst)):
phi_hat, phi_var = inf.phi_fit(Y_t, x0, hlst[i], theta_true, phi_sd,
gamma, False)
theta_euler[i] = inf.theta_sample(phi_hat, phi_var, n_samples)
# Parameter inference using Kalman solver
theta_kalman = np.zeros((len(hlst), n_samples, n_theta))
for i in range(len(hlst)):
ode_init = ibm_init(hlst[i], n_deriv_prior, sigma)
x0_state = zero_pad(X0, n_deriv, n_deriv_prior)
kinit = indep_init(ode_init, n_deriv_prior)
n_eval = int((tmax - tmin) / hlst[i])
kode = KalmanODE(W, tmin, tmax, n_eval, mseir, **kinit)
inf.kode = kode
inf.W = W
phi_hat, phi_var = inf.phi_fit(Y_t, x0_state, hlst[i], theta_true,
phi_sd, gamma, True)
theta_kalman[i] = inf.theta_sample(phi_hat, phi_var, n_samples)
# Produces the graph in Figure 4
inf.theta_plot(theta_euler, theta_kalman, theta_true, hlst)
return
# The rest of the parameters can be tuned according to ODE
# For this problem, we will use
n_var = 2
sigma = [.1] * n_var
# Initial value, x0, for the IVP
x0 = np.array([-1., 1.])
X0 = np.array([-1, 1, 1, 1 / 3])
w_mat = np.array([[0.0, 1.0, 0.0, 0.0], [0.0, 0.0, 0.0, 1.0]])
W = zero_pad(w_mat, n_deriv, n_deriv_prior)
x0_state = zero_pad(X0, n_deriv, n_deriv_prior)
theta = np.array([0.2, 0.2, 3])
# Get parameters needed to run the solver
dt = (tmax - tmin) / n_eval
ode_init = ibm_init(dt, n_deriv_prior, sigma)
kinit = indep_init(ode_init, n_deriv_prior)
z_state = rand_mat(n_eval, p)
# pick ode function with ndarray or ctuple inputs
ode_fun = ode_fun_ct if use_ctuple else ode_fun_nd
if use_ctuple:
theta = tuple(theta)
# Timings
n_loops = 100
# C++
kode_c = KalmanODE_c(W, tmin, tmax, n_eval, ode_fun, **kinit)
kode_c.z_state = z_state
time_c = timing(kode_c, x0_state, W, theta, n_loops)
def fitz_example():
"Perform parameter inference using the FitzHugh-Nagumo function."
# These parameters define the order of the ODE and the CAR(p) process
n_deriv = [1, 1] # Total state
n_deriv_prior = [3, 3]
state_ind = [0, 3] # Index of 0th derivative of each state
# it is assumed that the solution is sought on the interval [tmin, tmax].
tmin = 0
tmax = 40
# The rest of the parameters can be tuned according to ODE
# For this problem, we will use
n_var = 2
sigma = [.1] * n_var
# Initial value, x0, for the IVP
x0 = np.array([-1., 1.])
v0 = np.array([1, 1 / 3])
X0 = np.ravel([x0, v0], 'F')
# pad the inputs
w_mat = np.array([[0., 1., 0., 0.], [0., 0., 0., 1.]])
W = zero_pad(w_mat, n_deriv, n_deriv_prior)
x0_state = zero_pad(X0, n_deriv, n_deriv_prior)
# logprior parameters
theta_true = np.array([0.2, 0.2, 3]) # True theta
n_theta = len(theta_true)
phi_sd = np.ones(n_theta)
# Observation noise
gamma = 0.2
# Number of samples to draw from posterior
n_samples = 100000
# Initialize inference class and simulate observed data
inf = inference(state_ind, tmin, tmax, fitz)
Y_t = inf.simulate(fitz, x0, theta_true, gamma)
# Parameter inference using Euler's approximation
hlst = np.array([0.1, 0.05, 0.02, 0.01, 0.005])
theta_euler = np.zeros((len(hlst), n_samples, n_theta))
for i in range(len(hlst)):
phi_hat, phi_var = inf.phi_fit(Y_t, x0, hlst[i], theta_true, phi_sd,
gamma, False)
theta_euler[i] = inf.theta_sample(phi_hat, phi_var, n_samples)
# Parameter inference using Kalman solver
theta_kalman = np.zeros((len(hlst), n_samples, n_theta))
for i in range(len(hlst)):
ode_init = ibm_init(hlst[i], n_deriv_prior, sigma)
kinit = indep_init(ode_init, n_deriv_prior)
n_eval = int((tmax - tmin) / hlst[i])
kode = KalmanODE(W, tmin, tmax, n_eval, fitz, **kinit)
inf.kode = kode
inf.W = W
phi_hat, phi_var = inf.phi_fit(Y_t, x0_state, hlst[i], theta_true,
phi_sd, gamma, True)
theta_kalman[i] = inf.theta_sample(phi_hat, phi_var, n_samples)
# Produces the graph in Figure 3
inf.theta_plot(theta_euler, theta_kalman, theta_true, hlst)
return