Python wrapper with test for Legendre transform

python/libsharp/tests/__init__.py

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+# empty

python/libsharp/tests/test_legendre.py

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+import numpy as np
+from scipy.special import legendre
+import libsharp
+
+
+def test_legendre_transform():
+    lmax = 20
+    ntheta = 19
+
+    l = np.arange(lmax + 1)
+    bl = np.exp(-l*(l+1))
+    bl *= (2 * l + 1)
+
+    theta = np.linspace(0, np.pi, ntheta, endpoint=True)
+    x = np.cos(theta)
+
+    # Compute truth using scipy.special.legendre
+    P = np.zeros((ntheta, lmax + 1))
+    for l in range(lmax + 1):
+        P[:, l] = legendre(l)(x)
+    y0 = np.dot(P, bl)
+
+    # double-precision
+    y = libsharp.legendre_transform(x, bl)
+    assert np.max(np.abs(y - y) / np.abs(y)) < 1e-12
+
+    # single-precision
+    y32 = libsharp.legendre_transform(x.astype(np.float32), bl)
+    assert np.max(np.abs(y32 - y) / np.abs(y32)) < 1e-4