def test_tanh_forward():
A = Tanh()
x = np.linspace(-10, 10, 100)
y = np.tanh(x)
assert np.allclose(A.forward(x), y)
def test_tanh_backward():
A = Tanh()
x = np.linspace(-10, 10, 100)
dy = 1.0 - np.tanh(x)**2
grad = np.ones(x.size)
# The forward pass is needed to store the inputs used by the backward pass
A.forward(x)
assert np.allclose(A.backward(grad), dy)
def test_backpropagation_tanh_tanh_grad2():
"""
f(x) = tanh( tanh(x) )
f'(x) = tanh'( tanh(x) ) * tanh(x)
"""
nn: NeuralNetwork = NeuralNetwork([Tanh(), Tanh()])
input: Tensor = 0.5 * np.ones(1)
assert nn(input)[0] == pytest.approx(np.tanh(np.tanh(0.5)))
grad: float = 2
assert nn.backward(grad)[0] == pytest.approx(
grad * (1 - np.tanh(np.tanh(0.5)) ** 2) * (1 - np.tanh(0.5) ** 2)
)
def test_backpropagation_linear_tanh():
"""
f(x) = tanh( w * x + b )
f'(x) = tanh'(w * x + b) * w
"""
nn: NeuralNetwork = NeuralNetwork([Linear(1, 1), Tanh()])
nn.layers[0].params["w"] = np.array([[0.5]])
nn.layers[0].params["b"] = np.array([-0.5])
input: Tensor = 2 * np.ones(1)
assert nn(input) == pytest.approx(np.tanh(0.5))
grad: float = 1
assert nn.backward(grad)[0] == pytest.approx((1 - np.tanh(0.5) ** 2) * 0.5)
"""
Train neural network to learn the non-linear XOR function.
"""
from pynn.train import train
from pynn.nn import NeuralNetwork
from pynn.layer import Linear, Tanh
import numpy as np
inputs = np.array([[0, 0], [1, 0], [0, 1], [1, 1]])
targets = np.array([[1, 0], [0, 1], [0, 1], [1, 0]])
nn = NeuralNetwork([
Linear(input_size=2, output_size=2),
Tanh(),
Linear(input_size=2, output_size=2)
])
train(nn, inputs, targets)
for i, t in zip(inputs, targets):
predicted = nn(i)
print(i, np.around(predicted).astype(int), t)
def test_repr():
nn: NeuralNetwork = NeuralNetwork([Linear(10, 5), Tanh(), Linear(5, 2)])
assert (
repr(nn) == "NeuralNetwork([\n\tLinear(10, 5),\n\tTanh(),\n\tLinear(5, 2),\n])"
)
def test_linear_tanh_linear():
"""
import torch
import torch.nn as nn
torch.manual_seed(1234)
torch.set_printoptions(precision=10)
net = nn.Sequential(
nn.Linear(10, 5),
nn.Tanh(),
nn.Linear(5,2),
)
x = torch.rand(10)
print(f"x = {x}")
y = net(x)
print(f"y = {y}")
print(f"net[0].weight = {net[0].weight.data}")
print(f"net[0].bias = {net[0].bias.data}")
print(f"net[2].weight = {net[2].weight.data}")
print(f"net[2].bias = {net[2].bias.data}")
L = nn.MSELoss()
loss = L(y, torch.tensor([0.123, 0.234]))
print(loss.item())
loss.backward()
print(f"net[0].weight.grad = {net[0].weight.grad}")
print(f"net[0].bias.grad = {net[0].bias.grad}")
print(f"net[2].weight.grad = {net[2].weight.grad}")
print(f"net[2].bias.grad = {net[2].bias.grad}")
"""
# Define neural network
nn: NeuralNetwork = NeuralNetwork([Linear(10, 5), Tanh(), Linear(5, 2)])
# Define weight for first linear layer
nn.layers[0].params["w"] = np.array(
[
[
-0.2978996933,
-0.0620447993,
-0.1518878788,
-0.0843434185,
-0.2793551385,
0.1268988550,
-0.2834682167,
-0.0201505125,
0.1099246442,
-0.1065928042,
],
[
0.1794327199,
0.0398846865,
0.1738307178,
0.2028933465,
-0.1395977736,
0.1149241626,
-0.1368159652,
0.0991250277,
-0.1652253270,
0.1462771595,
],
[
0.0640188158,
-0.1237535626,
-0.1551083475,
0.0818156302,
0.2950474918,
0.1517572105,
-0.0305362642,
-0.0153491795,
0.1797402799,
-0.2197806835,
],
[
0.1051295400,
-0.1047832966,
0.1829633415,
-0.1128049493,
0.0156366825,
0.1067842245,
0.2173210084,
-0.0464802384,
0.2884919941,
-0.2675432563,
],
[
-0.0564081371,
-0.3153346777,
0.0261963010,
0.0897391737,
-0.1280111223,
0.1313367486,
-0.0512633622,
-0.2747980654,
0.2427785099,
0.1949744523,
],
]
).transpose()
# Define bias for first linear layer
nn.layers[0].params["b"] = np.array(
[0.1598871946, 0.2522428930, 0.1162832677, 0.1681351364, 0.2624163330]
)
# Define weight for second linear layer
nn.layers[2].params["w"] = np.array(
[
[-0.0901057720, -0.3487843573, -0.2199362069, -0.0596988499, -0.0491428077],
[-0.0030310154, 0.2562854886, 0.1434621215, -0.3306660652, -0.1343453825],
]
).transpose()
# Define bias for second
nn.layers[2].params["b"] = np.array([-0.1052068472, 0.2721802592])
# Input (batch_size=1)
x: Tensor = np.array(
[
[
0.3186104298,
0.2908077240,
0.4196097851,
0.3728144765,
0.3768919110,
0.0107794404,
0.9454936385,
0.7661116719,
0.2634066939,
0.1880336404,
]
]
)
# Compute prediction
y = nn(x)
# Check prediction value
assert np.allclose(y, [-0.2401246876, 0.2529487908])
# Loss function
L = MSE()
# Check loss value
assert L.loss(y, np.array([0.123, 0.234])) == pytest.approx(0.066109299659729)
# Compute loss gradient
grad = L.grad(y, np.array([0.123, 0.234]))
# Check there are no gradients before backpropagation
assert nn.layers[0].grads.get("w", None) is None
assert nn.layers[0].grads.get("b", None) is None
assert nn.layers[2].grads.get("w", None) is None
assert nn.layers[2].grads.get("b", None) is None
# Backpropagation
nn.backward(grad)
t = np.array(
[
[
0.0087200264,
0.0079590958,
0.0114842709,
0.0102035329,
0.0103151277,
0.0002950217,
0.0258771479,
0.0209676567,
0.0072091590,
0.0051462795,
],
[
0.0371894054,
0.0339441709,
0.0489784293,
0.0435163043,
0.0439922400,
0.0012582168,
0.1103615686,
0.0894234329,
0.0307458173,
0.0219479930,
],
[
0.0257711057,
0.0235222578,
0.0339405350,
0.0301554520,
0.0304852594,
0.0008719052,
0.0764771476,
0.0619676672,
0.0213059001,
0.0152092790,
],
[
0.0041744434,
0.0038101713,
0.0054977397,
0.0048846263,
0.0049380488,
0.0001412326,
0.0123878857,
0.0100376178,
0.0034511623,
0.0024636223,
],
[
0.0048741978,
0.0044488637,
0.0064193159,
0.0057034274,
0.0057658055,
0.0001649071,
0.0144644445,
0.0117202057,
0.0040296745,
0.0028765949,
],
]
).transpose()
assert np.allclose(nn.layers[0].grads["w"], t)
t = np.array(
[0.0273689292, 0.1167237535, 0.0808859468, 0.0131020295, 0.0152982995]
).transpose()
assert np.allclose(nn.layers[0].grads["b"], t)
t = np.array(
[
[0.1461823881, -0.1217547730, -0.0520500802, -0.1405923814, 0.0029136201],
[-0.0076281782, 0.0063534812, 0.0027161089, 0.0073364768, -0.0001520403],
]
).transpose()
assert np.allclose(nn.layers[2].grads["w"], t)
t = np.array([-0.3631246984, 0.0189487934]).transpose()
assert np.allclose(nn.layers[2].grads["b"], t)
def test_tanh_repr():
A = Tanh()
assert repr(A) == "Tanh()"