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trellis/utils/random_utils.py

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+import numpy as np
+
+PRIMES = [2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53]
+
+def radical_inverse(base, n):
+    val = 0
+    inv_base = 1.0 / base
+    inv_base_n = inv_base
+    while n > 0:
+        digit = n % base
+        val += digit * inv_base_n
+        n //= base
+        inv_base_n *= inv_base
+    return val
+
+def halton_sequence(dim, n):
+    return [radical_inverse(PRIMES[dim], n) for dim in range(dim)]
+
+def hammersley_sequence(dim, n, num_samples):
+    return [n / num_samples] + halton_sequence(dim - 1, n)
+
+def sphere_hammersley_sequence(n, num_samples, offset=(0, 0), remap=False):
+    u, v = hammersley_sequence(2, n, num_samples)
+    u += offset[0] / num_samples
+    v += offset[1]
+    if remap:
+        u = 2 * u if u < 0.25 else 2 / 3 * u + 1 / 3
+    theta = np.arccos(1 - 2 * u) - np.pi / 2
+    phi = v * 2 * np.pi
+    return [phi, theta]