def case_8():
'''Minimize Himmelblau's function.'''
def f(variables):
x, y = variables
return (x**2 + y - 11)**2 + (x + y**2 - 7)**2
f_string = 'f(x, y) = (x^2 + y - 11)^2 + (x + y^2 - 7)^2'
for x_val, y_val in [[5, 5]]:
x0 = da.Var(x_val, [1, 0])
y0 = da.Var(y_val, [0, 1])
init_vars = [x0, y0]
solution, xy_path, f_path = opt.GradientDescent(f,
init_vars,
iters=10000,
eta=0.01)
opt.plot_results(f,
xy_path,
f_path,
f_string,
threedim=True,
hide=True)
# Ensure that loss function is weakly decreasing
_assert_decreasing(f_path)
plt.close('all')
def case_7():
'''Minimize Easom's function.'''
def f(variables):
x, y = variables
return -np.cos(x) * np.cos(y) * np.exp(-((x - np.pi)**2 +
(y - np.pi)**2))
f_string = 'f(x, y) = -\cos(x)\cos(y)\exp(-((x-\pi)^2 + (y-\pi)^2))'
for x_val, y_val in [[1.5, 1.75]]:
x0 = da.Var(x_val, [1, 0])
y0 = da.Var(y_val, [0, 1])
init_vars = [x0, y0]
solution, xy_path, f_path = opt.GradientDescent(f,
init_vars,
iters=10000,
eta=0.3)
opt.plot_results(f,
xy_path,
f_path,
f_string,
threedim=True,
hide=True)
# Ensure that loss function is weakly decreasing
_assert_decreasing(f_path)
plt.close('all')
def case_5():
'''Minimize bowl function: f(x, y) = x^2 + y^2 + 2.
The global minimum is 2 when (x, y) = (0, 0).
'''
def f(variables):
x, y = variables
return x**2 + y**2 + 2
f_string = 'f(x, y) = x^2 + y^2 + 2'
for x_val, y_val in [[2., 3.], [-2., 5.]]:
x0 = da.Var(x_val, [1, 0])
y0 = da.Var(y_val, [0, 1])
init_vars = [x0, y0]
solution, xy_path, f_path = opt.GradientDescent(f, init_vars)
xn, yn = solution.val
opt.plot_results(f,
xy_path,
f_path,
f_string,
x_lims=(-7.5, 7.5),
threedim=True,
animate=True,
hide=True)
minimum = [0, 0]
assert np.allclose([xn, yn], minimum)
der = [0, 0]
assert np.allclose(solution.der, der)
plt.close('all')
def case_1():
'''Simple quadratic function with minimum at x = 0.'''
def f(x):
return x**2
f_string = 'f(x) = x^2'
for x_val in [-4, -2, 0, 2, 4]:
x0 = da.Var(x_val)
solution, x_path, f_path = opt.GradientDescent(f, x0)
opt.plot_results(f, x_path, f_path, f_string, hide=True)
assert np.allclose(solution.val, [0])
assert np.allclose(solution.der, [0])
plt.close('all')
def case_2():
def f(x):
return (x - 1)**2 + 3
f_string = 'f(x) = (x - 1)^2 + 3'
for x_val in [-3, -1, 1, 3, 5]:
# Test initial guess without using da.Var type
solution, x_path, f_path = opt.GradientDescent(f, x_val)
opt.plot_results(f,
x_path,
f_path,
f_string,
x_lims=(-3, 5),
y_lims=(2, 10),
animate=True,
hide=True)
assert np.allclose(solution.val, [1])
assert np.allclose(solution.der, [0])
plt.close('all')
def case_4():
'''Minimize Rosenbrock function: f(x, y) = 4(y - x^2)^2 + (1 - x)^2.
The global minimum is 0 when (x, y) = (1, 1).
'''
def f(variables):
x, y = variables
return 4 * (y - (x**2))**2 + (1 - x)**2
f_string = 'f(x, y) = 4(y - x^2)^2 + (1 - x)^2'
for x_val, y_val in [[-6., -6], [2., 3.], [-2., 5.]]:
x0 = da.Var(x_val, [1, 0])
y0 = da.Var(y_val, [0, 1])
init_vars = [x0, y0]
solution, xy_path, f_path = opt.GradientDescent(f,
init_vars,
iters=25000,
eta=0.002)
xn, yn = solution.val
opt.plot_results(f,
xy_path,
f_path,
f_string,
x_lims=(-7.5, 7.5),
threedim=True,
hide=True)
minimum = [1, 1]
assert np.allclose([xn, yn], minimum)
# dfdx = 2(200x^3 - 200xy + x - 1)
# dfdy = 200(y - x^2)
der_x = 2 * (8 * (xn**3) - 8 * xn * yn + xn - 1)
der_y = 8 * (yn - (xn**2))
assert np.allclose(solution.der, [der_x, der_y])
plt.close('all')
def case_3():
def f(x):
return np.sin(x)
f_string = 'f(x) = sin(x)'
for x_val in [-3, -1, 1, 3]:
# Test case when 1D input is a list
x0 = [da.Var(x_val)]
solution, x_path, f_path = opt.GradientDescent(f, x0)
opt.plot_results(f,
x_path,
f_path,
f_string,
x_lims=(-2 * np.pi, 2 * np.pi),
y_lims=(-1.5, 1.5),
hide=True)
multiple_of_three_halves_pi = (solution.val % (2 * np.pi))
np.testing.assert_array_almost_equal(multiple_of_three_halves_pi,
1.5 * np.pi)
np.testing.assert_array_almost_equal(solution.der, [0])
plt.close('all')
def case_6():
'''Minimize cost function of ML regression demo.
Note that we hardcode the dataset, since Travis CI does not recognize .txt files in the repository.
'''
# Standardized dataset: number of bedrooms, number of bathrooms, price
dataset = [
0.1300098691, -0.2236751872, 399900.0000000000, -0.5041898382,
-0.2236751872, 329900.0000000000, 0.5024763638, -0.2236751872,
369000.0000000000, -0.7357230647, -1.5377669118, 232000.0000000000,
1.2574760154, 1.0904165374, 539900.0000000000, -0.0197317285,
1.0904165374, 299900.0000000000, -0.5872397999, -0.2236751872,
314900.0000000000, -0.7218814044, -0.2236751872, 198999.0000000000,
-0.7810230438, -0.2236751872, 212000.0000000000, -0.6375731100,
-0.2236751872, 242500.0000000000, -0.0763567023, 1.0904165374,
239999.0000000000, -0.0008567372, -0.2236751872, 347000.0000000000,
-0.1392733400, -0.2236751872, 329999.0000000000, 3.1172918237,
2.4045082621, 699900.0000000000, -0.9219563121, -0.2236751872,
259900.0000000000, 0.3766430886, 1.0904165374, 449900.0000000000,
-0.8565230089, -1.5377669118, 299900.0000000000, -0.9622229602,
-0.2236751872, 199900.0000000000, 0.7654679091, 1.0904165374,
499998.0000000000, 1.2964843307, 1.0904165374, 599000.0000000000,
-0.2940482685, -0.2236751872, 252900.0000000000, -0.1417900055,
-1.5377669118, 255000.0000000000, -0.4991565072, -0.2236751872,
242900.0000000000, -0.0486733818, 1.0904165374, 259900.0000000000,
2.3773921652, -0.2236751872, 573900.0000000000, -1.1333562145,
-0.2236751872, 249900.0000000000, -0.6828730891, -0.2236751872,
464500.0000000000, 0.6610262907, -0.2236751872, 469000.0000000000,
0.2508098133, -0.2236751872, 475000.0000000000, 0.8007012262,
-0.2236751872, 299900.0000000000, -0.2034483104, -1.5377669118,
349900.0000000000, -1.2591894898, -2.8518586364, 169900.0000000000,
0.0494765729, 1.0904165374, 314900.0000000000, 1.4298676025,
-0.2236751872, 579900.0000000000, -0.2386816274, 1.0904165374,
285900.0000000000, -0.7092980769, -0.2236751872, 249900.0000000000,
-0.9584479619, -0.2236751872, 229900.0000000000, 0.1652431861,
1.0904165374, 345000.0000000000, 2.7863503098, 1.0904165374,
549000.0000000000, 0.2029931687, 1.0904165374, 287000.0000000000,
-0.4236565421, -1.5377669118, 368500.0000000000, 0.2986264579,
-0.2236751872, 329900.0000000000, 0.7126179335, 1.0904165374,
314000.0000000000, -1.0075229393, -0.2236751872, 299000.0000000000,
-1.4454227371, -1.5377669118, 179900.0000000000, -0.1870899846,
1.0904165374, 299900.0000000000, -1.0037479410, -0.2236751872,
239500.0000000000
]
dataset = np.reshape(dataset, [-1, 3])
dataset[:, 2] = dataset[:, 2] / 1000.
f_string = 'f(w_0, w_1, w_2) = (1/2m)\sum_{i=0}^m (w_0 + w_1x_{i1} + w_2x_{i2} - y_i)^2'
solution, w_path, f_path, f = opt.GradientDescent("mse", [0, 0, 0],
data=dataset)
opt.plot_results(f,
w_path,
f_path,
f_string,
x_lims=(-7.5, 7.5),
fourdim=True,
animate=True,
hide=True)
_assert_decreasing(f_path)
plt.close('all')