Fix GpuArrayType.values_eq_approx(). It wasn't checking the signe correctly.

theano/sandbox/gpuarray/tests/test_type.py

 import operator
 
+import numpy
+
 import theano
 from theano.compile import DeepCopyOp
 
@@ -18,3 +20,15 @@ def test_deep_copy():
     res = f(a)
 
     assert GpuArrayType.values_eq(res, a)
+
+
+def test_values_eq_approx():
+    a = rand_gpuarray(20, dtype='float32')
+    g = GpuArrayType(dtype='float32', broadcastable=(False,))('g')
+    assert GpuArrayType.values_eq_approx(a, a)
+    b = a.copy()
+    b[0] = numpy.asarray(b[0]) + 1.
+    assert not GpuArrayType.values_eq_approx(a, b)
+    b = a.copy()
+    b[0] = -numpy.asarray(b[0])
+    assert not GpuArrayType.values_eq_approx(a, b)

theano/sandbox/gpuarray/type.py

@@ -107,7 +107,7 @@ class GpuArrayType(Type):
             return GpuArrayType.values_eq(a, b)
         else:
             res = elemwise2(a, '', b, a, odtype=numpy.dtype('bool'),
-                            op_tmpl="res[i] = ((%(a)s - %(b)s) <"
+                            op_tmpl="res[i] = (fabs(%(a)s - %(b)s) <"
                             "(1e-8 + 1e-5 * fabs(%(b)s)))")
             return numpy.asarray(res).all()