[jira] [Commented] (CODEC-166) Base64 could be faster

["Emmanuel Bourg (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CODEC-166?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13644118#comment-13644118 ] 

Emmanuel Bourg commented on CODEC-166:
--------------------------------------

An observation regarding the benchmark, each implementation should be tested independently in a different run. When benchmarking the performance for Commons CSV I noticed that I got very different figures depending on the execution order of the tests. The only reliable way to measure the performance was to run the tests independently. Also the performance was quite different if I ran just the benchmark, or something else before (like the unit tests) and then the benchmark. And make sure you are running the server VM!
                
> Base64 could be faster
> ----------------------
>
>                 Key: CODEC-166
>                 URL: https://issues.apache.org/jira/browse/CODEC-166
>             Project: Commons Codec
>          Issue Type: Bug
>    Affects Versions: 1.7
>            Reporter: Julius Davies
>            Assignee: Julius Davies
>             Fix For: 2.0
>
>         Attachments: base64bench.zip, CODEC-166.patch, CODEC-166_speed.patch
>
>
> Our Base64 consistently performs 3 times slower compared to MiGBase64 and iHarder in the byte[] and String encode() methods.
> We are pretty good on decode(), though a little slower (approx. 33% slower) than MiGBase64.
> We always win in the Streaming methods (MiGBase64 doesn't do streaming).  Yay!  :-) :-) :-)
> I put together a benchmark.  Here's a typical run:
> {noformat}
>   LARGE DATA new byte[12345]
> iHarder...
> encode 486.0 MB/s    decode 158.0 MB/s
> encode 491.0 MB/s    decode 148.0 MB/s
> MiGBase64...
> encode 499.0 MB/s    decode 222.0 MB/s
> encode 493.0 MB/s    decode 226.0 MB/s
> Apache Commons Codec...
> encode 142.0 MB/s    decode 146.0 MB/s
> encode 138.0 MB/s    decode 150.0 MB/s
> {noformat}
> I believe the main approach we can consider to improve performance is to avoid array copies at all costs.   MiGBase64 even counts the number of valid Base64 characters ahead of time on decode() to precalculate the result's size and avoid any array copying!
> I suspect this will mean writing out separate execution paths for the String and byte[] methods, and keeping them out of the streaming logic, since the streaming logic is founded on array copy.
> Unfortunately this means we will diminish internal reuse of the streaming implementation, but I think it's the only way to improve performance, if we want to.

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