Performance of PER codec

[dudycz]

Hi. I have been playing with two most popular PER codecs: rasn and asn1-codecs and made some benchmark comparing their performance. One thing I have noticed is that rasn can be ~10x slower in encoding in some complex cases:

Codec	Encoding (µs)	Decoding (µs)
rasn	1916.7	826.8
asn1-codecs	208	145.5

I looked into flamegraphs and callgrinds but I couldn't figure out what contributes to this big difference. If you're interested I could try to collect some and attach here.

Link to repo with benchmark: https://github.com/dudycz/asn1_codecs_bench

[XAMPPRocky]

Thank you for your issue! Would you be able to attach the flamegraphs? That would be very helpful. In general the initial version I made prioritised correctness over performance so there's likely a lot of places where it could be more efficient. I already know that I haven't added the empty struct optimisation that was added to BER to PER.

[dudycz]

I had to encode sample.asn 256 times to get something recorded in flamegraph. Here it is:

[Nicceboy]

Seems like your test bench uses mostly integers. asn1-codecs crate seems to use i128 internally for Integer type while rasn uses BigInts. I would guess that this plays big factor at least.

I think there was a plan to make inner implementation of integer types as feature, so that it would be possible to select different internal type for performance reasons if very big numbers are not required.

[XAMPPRocky]

Yeah, that's still a todo, I should write up an issue giving details in case someone else who has more time is interested.

[Nicceboy]

Yeah, that's still a todo, I should write up an issue giving details in case someone else who has more time is interested.

I think this is rather important optimisation in general and should not take too much work to implement, if we have, for example, just the i128 and BigInts as initial options. If you have time to write what you had on your mind, maybe I can try to do it.