Merge pull request #12 from danielballan/remove-unneeded-copy

Remove unneeded copying.

autocorr/multitau.py

@@ -25,14 +25,14 @@ def even(x):
         return x if x % 2 == 0 else x - 1
 
     # 1-D data hack
-    if len(signal.shape) == 1:
+    if signal.ndim == 1:
         N = even(signal.shape[0])
-        a = np.array(signal[np.newaxis, :N], copy=True)
-    elif len(signal.shape) == 2:
+        a = signal[np.newaxis, :N]
+    elif signal.ndim == 2:
         # copy data a local array
         N = even(signal.shape[1])
-        a = np.array(signal[:, :N], copy=True)
-    elif len(signal.shape) > 2:
+        a = signal[:, :N]
+    elif signal.ndim > 2:
         raise ValueError('Flatten the [2,3,..] dimensions before passing to autocorrelate.')
 
     if N < lags_per_level:

autocorr/tests/test_multitau.py

@@ -1,36 +1,46 @@
 import numpy as np
+from numpy.testing import assert_array_equal
 import autocorr
 import time
 
 N = 10240
 np.random.seed(0)
 t = np.arange(N)
 A = np.exp(-0.05 * t)[:, np.newaxis] + np.random.rand(N, 24) * 0.1
+original = A.copy()
 
 
 def test_multitau():
     t0 = time.time()
     g1, tau = autocorr.multitau(A.T, 16)
     t1 = time.time()
+    # Check that the input array has not been mutated.
+    assert_array_equal(A, original)
     print('pure python time = %f' % (t1 - t0))
 
 
 def test_multitau_mt():
     t0 = time.time()
     g1, tau = autocorr.multitau_mt(A.T, 16)
     t1 = time.time()
+    # Check that the input array has not been mutated.
+    assert_array_equal(A, original)
     print('accelerated version = %f' % (t1 - t0))
 
 
 def test_fftautocorr():
     t0 = time.time()
     g2, tau = autocorr.fftautocorr(A.T)
     t1 = time.time()
+    # Check that the input array has not been mutated.
+    assert_array_equal(A, original)
     print('fft version = %f' % (t1 - t0))
 
 
 def test_cfftautocorr():
     t0 = time.time()
     g2, tau = autocorr.fftautocorr_mt(A.T)
     t1 = time.time()
+    # Check that the input array has not been mutated.
+    assert_array_equal(A, original)
     print('fft version = %f' % (t1 - t0))