Speed up Decode and Encode timing

[xRowe]

I see there is a old thread on this topic, check if this topic can be carried on.

362

Is there any new solution to speed up decoding and encoding timing?

Online receving Messages by python-can and decoding: canmatrix v.s cantools

Example Test Code

def on_message_received(msg):
        start = time.perf_counter_ns()

        dbc_msg = _database.frame_by_id(msg.arbitration_id)

        # start = time.perf_counter_ns()
        decoded = dbc_msg.decode(msg.data)
        end = time.perf_counter_ns()

       timings.append(end-start)

canmatrix decode Mean +- std dev: 49.1 us +- 36.5 us (2207 values) Mean +- std dev: 97.4 us +- 182.5 us (12201 values) received_message + decode Mean +- std dev: 147.1 us +- 157.3 us (12201 values)

cantools decode Mean +- std dev: 30.0 us +- 29.9 us (2200 values) Mean +- std dev: 34.8 us +- 35.9 us (12201 values) received_message + decode Mean +- std dev: 64.9 us +- 57.7 us (12201 values)

After looking at cantools solution, after database is parsed, it will generate a _codec info which allowed to more quickly encode/decode a message, and generate two dicts which allow quick search message by name or id.

But canmatrix, everytime when receive a raw message, I need to found it in database by using for test in self.frames:, when call decode() method, it try to upack the data by bytes_to_bitstrings() and bitstring_to_signal_list(), which also using for loop.

I do not if bitsruct may help better, and refer to cantools

[ebroecker]

Hi @xRowe

thanks for doing the measurements!

It would be easy to implement some dictionary to allow quick search message by name or id. Thus I'm gonna implement such a hash-table which I think is a good idea.

Bitstruct on the other hand is (or at least was) not able to handle multiplexed messages. Multiplexer enables messages(=frames/pdus) to have different layouts depending on the content of some bits.

[xRowe]

Thanks for your reply.

There are commits along with implementing the DICTs already,

https://github.com/ebroecker/canmatrix/blob/e7ce2aa5e48d1d1bdb6226f35154e05c947dbf50/src/canmatrix/canmatrix.py#L1994-L2002 https://github.com/ebroecker/canmatrix/blob/e7ce2aa5e48d1d1bdb6226f35154e05c947dbf50/src/canmatrix/canmatrix.py#L2029-L2036

And I create/add the data here, but I think the way is not good enough, and not cover all the cases. https://github.com/ebroecker/canmatrix/blob/e7ce2aa5e48d1d1bdb6226f35154e05c947dbf50/src/canmatrix/canmatrix.py#L2075-L2089

Though my project is running these code, I did not run the benchmark then.

If you have better idea, please improve it.

Thanks, Rowe