added tensor functions: min, argmin, smallest. Fixed scalar return-value bug in MaxAndArgMax

theano/tensor/basic.py

@@ -809,8 +809,8 @@ class MaxAndArgmax(Op):
                    tensor(axis.type.dtype, broadcastable)]
         return Apply(self, inputs, outputs)
     def perform(self, node, (x, axis), (max, max_idx)):
-        max[0] = numpy.max(x, axis)
-        max_idx[0] = numpy.argmax(x, axis)
+        max[0] = numpy.asarray(numpy.max(x, axis))
+        max_idx[0] = numpy.asarray(numpy.argmax(x, axis))
     def grad(self, (x, axis), (g_max, g_max_idx)):
         # @warning: This only works if axis is 0, else the max is
         # broadcasted wrong in the call to eq.
@@ -859,6 +859,27 @@ def argmax(x, axis=None):
     # but when Argmax.c_impl() is in place, it should be fine.
     return max_and_argmax(x,axis)[1]
 
+@constructor
+def min(x, axis=None):
+    if 'float'in str(x.dtype):
+        return -max(-x, axis=axis)
+    else:
+        #Be careful about unsigned integers, complex
+        raise NotImplementedError()
+
+@constructor
+def argmin(x, axis=None):
+    if 'float'in str(x.dtype):
+        return argmax(-x, axis=axis)
+    else:
+        #Be careful about unsigned integers, complex
+        raise NotImplementedError()
+
+@constructor
+def smallest(*args):
+    """Return the [elementwise] smallest of a variable number of arguments (like python's min)."""
+    return min(stack(*args), axis=0)
+
 
 ##########################
 # Comparison

theano/tensor/tests/test_basic.py

@@ -1767,6 +1767,27 @@ class test_tensordot(unittest.TestCase):
                                       f6(bval,aval)))
             tensor.verify_grad(None, TensorDot(axes), [bval,aval])
 
+def test_smallest_stack():
+    sx, sy = dscalar(), dscalar()
+
+    rval = function([sx,sy], stack(sx,sy))(-4.0, -2.0)
+    assert type(rval) == numpy.ndarray
+    assert [-4, -2] == list(rval)
+
+def test_smallest():
+    x = dvector()
+    y = dvector()
+    z = dvector()
+    f1 = function([x], smallest(x))
+    assert numpy.all([1,2,3] == f1([1,2,3]))
+    f3 = function([x,y,z], smallest(x,y,z))
+    assert numpy.all([1,2,3] == f3([1,3,9], [7,7,7], [8,2,3]))
+
+    sx, sy = dscalar(), dscalar()
+
+    assert -4 == function([sx,sy], smallest(sx,sy))(-4.0, -2.0)
+
+
 
 if __name__ == '__main__':
     if len(sys.argv) >= 2 and sys.argv[1] == 'OPT':