Function test_stack1

tests/python/test_docexamples.py:204–246

()

def test_stack1():
    # Define the two parts of the message and their respective entropy models:
    message_part1 = np.array([1, 2, 0, 3, 2, 3, 0], dtype=np.int32)
    probabilities_part1 = np.array([0.2, 0.4, 0.1, 0.3], dtype=np.float64)
    model_part1 = constriction.stream.model.Categorical(probabilities_part1, perfect=False)
    # `model_part1` is a categorical distribution over the (implied) alphabet
    # {0,1,2,3} with P(X=0) = 0.2, P(X=1) = 0.4, P(X=2) = 0.1, and P(X=3) = 0.3;
    # we will use it below to encode each of the 7 symbols in `message_part1`.

    message_part2 = np.array([6,   10,   -4,    2], dtype=np.int32)
    means_part2 = np.array([2.5, 13.1, -1.1, -3.0], dtype=np.float64)
    stds_part2 = np.array([4.1,  8.7,  6.2,  5.4], dtype=np.float64)
    model_family_part2 = constriction.stream.model.QuantizedGaussian(-100, 100)
    # `model_family_part2` is a *family* of Gaussian distributions, quantized to
    # bins of width 1 centered at the integers -100, -99, ..., 100. We could
    # have provided a fixed mean and standard deviation to the constructor of
    # `QuantizedGaussian` but we'll instead provide individual means and standard
    # deviations for each symbol when we encode and decode `message_part2` below.

    print(
        f"Original message: {np.concatenate([message_part1, message_part2])}")

    # Encode both parts of the message in sequence (in reverse order):
    coder = constriction.stream.stack.AnsCoder()
    coder.encode_reverse(
        message_part2, model_family_part2, means_part2, stds_part2)
    coder.encode_reverse(message_part1, model_part1)

    # Get and print the compressed representation:
    compressed = coder.get_compressed()
    print(f"compressed representation: {compressed}")
    print(f"(in binary: {[bin(word) for word in compressed]})")

    # You could save `compressed` to a file using `compressed.tofile("filename")`,
    # read it back in: `compressed = np.fromfile("filename", dtype=np.uint32) and
    # then re-create `coder = constriction.stream.stack.AnsCoder(compressed)`.

    # Decode the message:
    decoded_part1 = coder.decode(model_part1, 7)  # (decodes 7 symbols)
    decoded_part2 = coder.decode(model_family_part2, means_part2, stds_part2)
    print(f"Decoded message: {np.concatenate([decoded_part1, decoded_part2])}")
    assert np.all(decoded_part1 == message_part1)
    assert np.all(decoded_part2 == message_part2)


def test_stack2():