typed_list – Typed List

Note

This has been added in release 0.7.

Note

This works, but is not well integrated with the rest of Theano. If speed is important, it is probably better to pad to a dense tensor.

This is a type that represents a list in Theano. All elements must have the same Theano type. Here is an example:

import theano.typed_list

tl = theano.typed_list.TypedListType(theano.tensor.fvector)()
v = theano.tensor.fvector()
o = theano.typed_list.append(tl, v)
f = theano.function([tl, v], o)
print f([[1, 2, 3], [4, 5]], [2])
#[array([ 1.,  2.,  3.], dtype=float32), array([ 4.,  5.], dtype=float32), array([ 2.], dtype=float32)]

A second example with Scan. Scan doesn’t yet have direct support of TypedList, so you can only use it as non_sequences (not in sequences or as outputs):

import theano.typed_list

a = theano.typed_list.TypedListType(theano.tensor.fvector)()
l = theano.typed_list.length(a)
s, _ = theano.scan(fn=lambda i, tl: tl[i].sum(),
                   non_sequences=[a],
                   sequences=[theano.tensor.arange(l, dtype='int64')])

f = theano.function([a], s)
f([[1, 2, 3], [4, 5]])
#array([ 6.,  9.], dtype=float32)