Python wrapper with test for Legendre transform

python/fake_pyrex/Pyrex/Distutils/__init__.py

@@ -0,0 +1 @@
+# work around broken setuptools monkey patching

python/fake_pyrex/Pyrex/Distutils/build_ext.py

@@ -0,0 +1 @@
+build_ext = "yes, it's there!"

python/fake_pyrex/Pyrex/__init__.py

@@ -0,0 +1 @@
+# work around broken setuptools monkey patching

python/fake_pyrex/README

@@ -0,0 +1,2 @@
+This directory is here to fool setuptools into building .pyx files
+even if Pyrex is not installed. See ../setup.py.

python/libsharp/__init__.py

@@ -0,0 +1 @@
+from .libsharp import *

python/libsharp/libsharp.pyx

@@ -0,0 +1,41 @@
+import numpy as np
+
+cdef extern from "sharp.h":
+    ctypedef long ptrdiff_t
+
+    void sharp_legendre_transform_s(float *bl, float *recfac, ptrdiff_t lmax, float *x,
+                                    float *out, ptrdiff_t nx)
+    void sharp_legendre_transform(double *bl, double *recfac, ptrdiff_t lmax, double *x,
+                                  double *out, ptrdiff_t nx)
+    void sharp_legendre_transform_recfac(double *r, ptrdiff_t lmax)
+    void sharp_legendre_transform_recfac_s(float *r, ptrdiff_t lmax)
+
+
+def legendre_transform(x, bl, out=None):
+    if out is None:
+        out = np.empty_like(x)
+    if x.dtype == np.float64:
+        if bl.dtype != np.float64:
+            bl = bl.astype(np.float64)
+        return _legendre_transform(x, bl, out=out)
+    elif x.dtype == np.float32:
+        if bl.dtype != np.float32:
+            bl = bl.astype(np.float32)
+        return _legendre_transform_s(x, bl, out=out)
+    else:
+        raise ValueError("unsupported dtype")
+
+
+def _legendre_transform(double[::1] x, double[::1] bl, double[::1] out):
+    if out.shape[0] != x.shape[0]:
+        raise ValueError('x and out must have same shape')
+    sharp_legendre_transform(&bl[0], NULL, bl.shape[0] - 1, &x[0], &out[0], x.shape[0])
+    return np.asarray(out)
+
+
+def _legendre_transform_s(float[::1] x, float[::1] bl, float[::1] out):
+    if out.shape[0] != x.shape[0]:
+        raise ValueError('x and out must have same shape')
+    sharp_legendre_transform_s(&bl[0], NULL, bl.shape[0] - 1, &x[0], &out[0], x.shape[0])
+    return np.asarray(out)
+

python/libsharp/tests/__init__.py

@@ -0,0 +1 @@
+# empty

python/libsharp/tests/test_legendre.py

@@ -0,0 +1,29 @@
+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

python/setup.py

@@ -0,0 +1,76 @@
+#! /usr/bin/env python
+
+descr   = """Spherical Harmionic transforms package
+
+Python API for the libsharp spherical harmonic transforms library
+"""
+
+import os
+import sys
+
+DISTNAME            = 'libsharp'
+DESCRIPTION         = 'libsharp library for fast Spherical Harmonic Transforms'
+LONG_DESCRIPTION    = descr
+MAINTAINER          = 'Dag Sverre Seljebotn',
+MAINTAINER_EMAIL    = 'd.s.seljebotn@astro.uio.no',
+URL                 = 'http://sourceforge.net/projects/libsharp/'
+LICENSE             = 'GPL'
+DOWNLOAD_URL        = "http://sourceforge.net/projects/libsharp/"
+VERSION             = '0.1'
+
+# Add our fake Pyrex at the end of the Python search path
+# in order to fool setuptools into allowing compilation of
+# pyx files to C files. Importing Cython.Distutils then
+# makes Cython the tool of choice for this rather than
+# (the possibly nonexisting) Pyrex.
+project_path = os.path.split(__file__)[0]
+sys.path.append(os.path.join(project_path, 'fake_pyrex'))
+
+from setuptools import setup, find_packages, Extension
+from Cython.Distutils import build_ext
+import numpy as np
+
+libsharp = os.environ.get('LIBSHARP', None)
+libsharp_include = os.environ.get('LIBSHARP_INCLUDE', libsharp and os.path.join(libsharp, 'include'))
+libsharp_lib = os.environ.get('LIBSHARP_LIB', libsharp and os.path.join(libsharp, 'lib'))
+
+if libsharp_include is None or libsharp_lib is None:
+    sys.stderr.write('Please set LIBSHARP environment variable to the install directly of libsharp, '
+                     'this script will refer to the lib and include sub-directories. Alternatively '
+                     'set LIBSHARP_INCLUDE and LIBSHARP_LIB\n')
+    sys.exit(1)
+
+if __name__ == "__main__":
+    setup(install_requires = ['numpy'],
+          packages = find_packages(),
+          test_suite="nose.collector",
+          # Well, technically zipping the package will work, but since it's
+          # all compiled code it'll just get unzipped again at runtime, which
+          # is pointless:
+          zip_safe = False,
+          name = DISTNAME,
+          version = VERSION,
+          maintainer = MAINTAINER,
+          maintainer_email = MAINTAINER_EMAIL,
+          description = DESCRIPTION,
+          license = LICENSE,
+          url = URL,
+          download_url = DOWNLOAD_URL,
+          long_description = LONG_DESCRIPTION,
+          classifiers =
+            [ 'Development Status :: 3 - Alpha',
+              'Environment :: Console',
+              'Intended Audience :: Developers',
+              'Intended Audience :: Science/Research',
+              'License :: OSI Approved :: GNU General Public License (GPL)',
+              'Topic :: Scientific/Engineering'],
+          cmdclass = {"build_ext": build_ext},
+          ext_modules = [
+              Extension("libsharp.libsharp",
+                        ["libsharp/libsharp.pyx"],
+                        libraries=["sharp", "fftpack", "c_utils"],
+                        include_dirs=[libsharp_include],
+                        library_dirs=[libsharp_lib]
+                        ),
+              ],
+          )