Merge pull request #583 from acq4/function-updates

Function updates

pyqtgraph/functions.py

@@ -15,7 +15,7 @@ from .python2_3 import asUnicode, basestring
 from .Qt import QtGui, QtCore, USE_PYSIDE
 from . import getConfigOption, setConfigOptions
 from . import debug
-
+from .metaarray import MetaArray
 
 
 Colors = {
@@ -417,7 +417,21 @@ def eq(a, b):
     """
     if a is b:
         return True
-        
+
+    # Avoid comparing large arrays against scalars; this is expensive and we know it should return False.
+    aIsArr = isinstance(a, (np.ndarray, MetaArray))
+    bIsArr = isinstance(b, (np.ndarray, MetaArray))
+    if (aIsArr or bIsArr) and type(a) != type(b):
+        return False
+
+    # If both inputs are arrays, we can speeed up comparison if shapes / dtypes don't match
+    # NOTE: arrays of dissimilar type should be considered unequal even if they are numerically
+    # equal because they may behave differently when computed on.
+    if aIsArr and bIsArr and (a.shape != b.shape or a.dtype != b.dtype):
+        return False
+
+    # Test for equivalence. 
+    # If the test raises a recognized exception, then return Falase
     try:
         try:
             # Sometimes running catch_warnings(module=np) generates AttributeError ???
@@ -733,26 +747,17 @@ def subArray(data, offset, shape, stride):
     the input in the example above to have shape (10, 7) would cause the
     output to have shape (2, 3, 7).
     """
-    #data = data.flatten()
-    data = data[offset:]
+    data = np.ascontiguousarray(data)[offset:]
     shape = tuple(shape)
-    stride = tuple(stride)
     extraShape = data.shape[1:]
-    #print data.shape, offset, shape, stride
-    for i in range(len(shape)):
-        mask = (slice(None),) * i + (slice(None, shape[i] * stride[i]),)
-        newShape = shape[:i+1]
-        if i < len(shape)-1:
-            newShape += (stride[i],)
-        newShape += extraShape 
-        #print i, mask, newShape
-        #print "start:\n", data.shape, data
-        data = data[mask]
-        #print "mask:\n", data.shape, data
-        data = data.reshape(newShape)
-        #print "reshape:\n", data.shape, data
+
+    strides = list(data.strides[::-1])
+    itemsize = strides[-1]
+    for s in stride[1::-1]:
+        strides.append(itemsize * s)
+    strides = tuple(strides[::-1])
     
-    return data
+    return np.ndarray(buffer=data, shape=shape+extraShape, strides=strides, dtype=data.dtype)
 
 
 def transformToArray(tr):

pyqtgraph/tests/test_functions.py

@@ -344,14 +344,14 @@ def test_eq():
     a2 = a1 + 1
     a3 = a2.astype('int')
     a4 = np.empty((0, 20))
-    assert not eq(a1, a2)
-    assert not eq(a1, a3)
-    assert not eq(a1, a4)
+    assert not eq(a1, a2)  # same shape/dtype, different values
+    assert not eq(a1, a3)  # same shape, different dtype and values
+    assert not eq(a1, a4)  # different shape (note: np.all gives True if one array has size 0)
 
-    assert eq(a2, a3)
-    assert not eq(a2, a4)
+    assert not eq(a2, a3)  # same values, but different dtype
+    assert not eq(a2, a4)  # different shape
     
-    assert not eq(a3, a4)
+    assert not eq(a3, a4)  # different shape and dtype
     
     assert eq(a4, a4.copy())
     assert not eq(a4, a4.T)