def testWhile(self):
with NetBuilder(_use_control_ops=True) as nb:
ops.Copy(ops.Const(0), "i")
ops.Copy(ops.Const(1), "one")
ops.Copy(ops.Const(2), "two")
ops.Copy(ops.Const(2.0), "x")
ops.Copy(ops.Const(3.0), "y")
ops.Copy(ops.Const(2.0), "z")
# raises x to the power of 4 and y to the power of 2
# and z to the power of 3
with ops.WhileNet():
with ops.Condition():
ops.Add(["i", "one"], "i")
ops.LE(["i", "two"])
ops.Pow("x", "x", exponent=2.0)
with ops.IfNet(ops.LT(["i", "two"])):
ops.Pow("y", "y", exponent=2.0)
with ops.Else():
ops.Pow("z", "z", exponent=3.0)
ops.Add(["x", "y"], "x_plus_y")
ops.Add(["x_plus_y", "z"], "s")
assert len(nb.get()) == 1, "Expected a single net produced"
net = nb.get()[0]
net.AddGradientOperators(["s"])
workspace.RunNetOnce(net)
# (x^4)' = 4x^3
self.assertAlmostEqual(workspace.FetchBlob("x_grad"), 32)
self.assertAlmostEqual(workspace.FetchBlob("x"), 16)
# (y^2)' = 2y
self.assertAlmostEqual(workspace.FetchBlob("y_grad"), 6)
self.assertAlmostEqual(workspace.FetchBlob("y"), 9)
# (z^3)' = 3z^2
self.assertAlmostEqual(workspace.FetchBlob("z_grad"), 12)
self.assertAlmostEqual(workspace.FetchBlob("z"), 8)
# As a result, in order to see values computed by a block after the block is finished the corresponding blobs have to be defined outside of the block. Note, that this is one of the ways to solve the problem with uninitialized blobs (e.g. blob created by 'then' branch, but not by 'else' branch), these rules effectively force visible blobs to be always correctly initialized.
# To illustrate concepts of block semantics and provide a more sophisticated example, let's consider the following net:
# In[4]:
with NetBuilder() as nb:
ops.Const(0.0, blob_out="zero")
ops.Const(1.0, blob_out="one")
ops.Const(2.0, blob_out="two")
ops.Const(1.5, blob_out="x")
ops.Const(0.0, blob_out="y")
with ops.IfNet(ops.GT(["x", "zero"])):
ops.Copy("x", "local_blob")
with ops.IfNet(ops.LE(["local_blob", "one"])):
ops.Copy("one", "y")
with ops.Else():
ops.Copy("two", "y")
with ops.Else():
ops.Copy("zero", "y")
# ops.Copy("local_blob", "z") - fails with exception during net construction, local_blob is undefined
# In[5]:
plan = Plan('if_net_test_2')
plan.AddStep(to_execution_step(nb))
ws = workspace.C.Workspace()
ws.run(plan)
print('x = ', ws.blobs["x"].fetch())
print('y = ', ws.blobs["y"].fetch())