def backward_pass(g, end_node):
outgrads = {end_node: g}
for node in toposort(end_node):
outgrad = outgrads.pop(node)
fun, value, args, kwargs, argnums = node.recipe
for argnum, parent in zip(argnums, node.parents):
vjp = primitive_vjps[fun][argnum]
parent_grad = vjp(outgrad, value, *args, **kwargs)
outgrads[parent] = add_outgrads(outgrads.get(parent), parent_grad)
return outgrad
def test_large_example():
"""Taken from http://code.activestate.com/recipes/577413-topological-sort/"""
data = {
'des_system_lib': set('std synopsys std_cell_lib des_system_lib dw02 dw01 ramlib ieee'.split()),
'dw01': set('ieee dw01 dware gtech'.split()),
'dw02': set('ieee dw02 dware'.split()),
'dw03': set('std synopsys dware dw03 dw02 dw01 ieee gtech'.split()),
'dw04': set('dw04 ieee dw01 dware gtech'.split()),
'dw05': set('dw05 ieee dware'.split()),
'dw06': set('dw06 ieee dware'.split()),
'dw07': set('ieee dware'.split()),
'dware': set('ieee dware'.split()),
'gtech': set('ieee gtech'.split()),
'ramlib': set('std ieee'.split()),
'std_cell_lib': set('ieee std_cell_lib'.split()),
'synopsys': set(),
}
result = toposort(data)
answer = ('ieee std synopsys dware gtech ramlib std_cell_lib '
'dw01 dw02 dw05 dw06 dw07 des_system_lib dw03 dw04').split()
assert result == answer
def test_toposort_adds_orphan_vertices():
data = {'a' : set('b')}
assert toposort(data) == ['b', 'a']
def test_empty_dependency():
assert toposort({'a':set()}) == ['a']
def test_empty_data():
assert toposort({}) == []
def test_not_dict():
""" Error raised if data not a dist """
with pytest.raises(TypeError) as exc:
toposort('3')
assert exc.value.args[0] == 'Data must be a dictionary of sets'
def test_not_set():
"""Error raised if values not sets"""
data = {'a' : ['a', 'b']}
with pytest.raises(TypeError) as exc:
toposort(data)
assert exc.value.args[0] == 'All values must be sets'
def test_toposort_simple():
data = {'a' : set('b'),
'b' : set()}
assert toposort(data) == ['b', 'a']
def test_ignore_self_dependencies():
data = {'a' : set('ab')}
assert toposort(data) == ['b', 'a']
def test_error_on_cycle():
data = {'a' : set('b'),
'b' : set('a')}
with pytest.raises(TypeError) as exc:
toposort(data)
assert exc.value.args[0].startswith('A cyclic dependency')
def test_toposort_subsorts():
"""After dependency sorting, normal sorting used"""
data = {'a' : set('cbfjq')}
assert toposort(data) == ['b', 'c', 'f', 'j', 'q', 'a']
def toposort(self):
""" Order computations in an executable order """
return toposort(self.dict_io())
def ordered_expressions(self):
return toposort(self.dependency_graph())