1 files changed, 91 insertions, 0 deletions
diff --git a/plots.py b/plots.py
new file mode 100644
index 0000000..dd4706b
--- /dev/null
+++ b/plots.py
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+import matplotlib.pyplot as plt
+from matplotlib.gridspec import GridSpec
+import numpy as np
+from torchvision import datasets
+
+
+def q_xt_x0(x0, t):
+    alpha_bar = ALPHA_BAR[t]
+    mean = np.sqrt(alpha_bar) * x0
+    std = np.sqrt(1 - alpha_bar)
+
+    eps = np.random.normal(0, 1, x0.shape)
+    xt = mean + std * eps
+
+    return xt, eps
+
+def q_xt_xt_1(xt_1, t):
+    alpha = ALPHA[t]
+    mean = np.sqrt(alpha) * xt_1
+    std = np.sqrt(1 - alpha)
+
+    eps = np.random.normal(0, 1, xt_1.shape)
+    xt = mean + std * eps
+
+    return xt, eps
+
+
+DIFFU_STEPS = 1000
+BETA = np.linspace(1e-4, 2e-2, DIFFU_STEPS)
+ALPHA = 1 - BETA
+ALPHA_BAR = np.cumprod(ALPHA)
+
+NB_BINS = 50
+BIN_MIN = -4
+BIN_MAX = 4
+
+
+plt.figure()
+plt.plot(BETA, label='beta')
+plt.plot(ALPHA, label='alpha')
+plt.plot(ALPHA_BAR, label='alpha_bar')
+plt.legend()
+plt.title('Alpha, Beta and Alpha_bar schedules')
+plt.savefig('plots/alpha_beta.tmp.png')
+
+
+mnist = datasets.MNIST('data', train=True, download=True)
+img = mnist.data[np.random.randint(0, len(mnist))].numpy() / 255
+
+plt.figure()
+plt.imshow(img, cmap='gray')
+plt.title('Image')
+plt.axis('off')
+plt.savefig('plots/img.tmp.png')
+
+
+plt.figure()
+plt.hist(img.flatten(), bins=NB_BINS, range=(BIN_MIN, BIN_MAX))
+plt.yscale('log')
+plt.title('Image histogram')
+plt.savefig('plots/img_hist.tmp.png')
+
+
+def norm_dist(x, mean, std):
+    return np.exp(-0.5 * ((x - mean) / std) ** 2) / (std * np.sqrt(2 * np.pi))
+
+x_norm = np.linspace(BIN_MIN, BIN_MAX, 100)
+y_norm = norm_dist(x_norm, 0, 1) * 28**2 / NB_BINS * (BIN_MAX - BIN_MIN)
+
+fig = plt.figure(figsize=(10, 5))
+gs = GridSpec(1, 3, figure=fig)
+ax1 = fig.add_subplot(gs[0, 0])
+ax2 = fig.add_subplot(gs[0, 1:])
+
+xt = img
+for t in range(DIFFU_STEPS):
+    xt, eps = q_xt_xt_1(xt, t)
+
+    ax1.clear()
+    ax1.imshow(xt, cmap='gray')
+    ax1.set_title(f'xt at t={t}')
+    ax1.axis('off')
+
+    ax2.clear()
+    ax2.hist(xt.flatten(), bins=NB_BINS, range=(BIN_MIN, BIN_MAX))
+    ax2.plot(x_norm, y_norm, color='red', label='N(0, 1)')
+    ax2.set_yscale('log')
+    ax2.set_ylim(y_norm.min(), 1e3)
+    ax2.set_title(f'xt histogram')
+
+    fig.savefig(f'plots/diffusion/{t:04d}.tmp.png')