Hi Andrew!
On 4/9/19 9:05 AM, Andrew Leonard wrote:
Hi Ivan,
Your micro benchmarks look good, that's something I need to learn how
to execute.
Here's how I ran them from the command line:
make test TEST="micro:java.lang.StringBuilders.from"
MICRO="FORK=3;WARMUP_ITER=4;ITER=6;WARMUP_TIME=4;TIME=4"
Do we think this is a good resolution now?
Yes. I'll go ahead and push it shortly.
With kind regards,
Ivan
Thanks
Andrew
Andrew Leonard
Java Runtimes Development
IBM Hursley
IBM United Kingdom Ltd
Phone internal: 245913, external: 01962 815913
internet email: [email protected]
From: Ivan Gerasimov <[email protected]>
To: Roger Riggs <[email protected]>, Andrew Leonard
<[email protected]>
Cc: [email protected]
Date: 06/04/2019 06:44
Subject: Re: Request for sponsor: JDK-8221430:
StringBuffer(CharSequence) constructor truncates when
-XX:-CompactStrings specified
------------------------------------------------------------------------
Hi Roger!
On 4/1/19 8:06 AM, Roger Riggs wrote:
> Hi Ivan,
>
> Thanks for running the micro benchmarks.
>
> This version has more code duplication than Andrew's original
> proposal that calculated the coder only CharSequence and had
> a single AbstractStringBuilder constructor for computing the size
> and allocating the byte[]/
>
> http://cr.openjdk.java.net/~aleonard/8221430/webrev.00/
<http://cr.openjdk.java.net/%7Ealeonard/8221430/webrev.00/>
>
> I'd be curious to know the JMH tests for that version compared.
>
That variant appeared to be slightly slower, comparing to the latest
variant:
Here are fresh benchmarks for both variants
(1) cr.openjdk.java.net/~aleonard/8221430/webrev.00 :
Benchmark Mode Cnt Score Error Units
StringBuilders.fromLatin1String avgt 18 15.217 ± 0.157 ns/op
StringBuilders.fromLatin1StringBuilder avgt 18 19.169 ± 0.086 ns/op
StringBuilders.fromUtf16String avgt 18 17.593 ± 0.180 ns/op
StringBuilders.fromUtf16StringBuilder avgt 18 21.786 ± 0.158 ns/op
(2) cr.openjdk.java.net/~igerasim/8221430/02/webrev :
Benchmark Mode Cnt Score Error Units
StringBuilders.fromLatin1String avgt 18 14.655 ± 0.133 ns/op
StringBuilders.fromLatin1StringBuilder avgt 18 18.059 ± 0.161 ns/op
StringBuilders.fromUtf16String avgt 18 16.675 ± 0.124 ns/op
StringBuilders.fromUtf16StringBuilder avgt 18 20.761 ± 0.116 ns/op
One reason might be that (2) avoids a redundant check for negative
length of the String argument.
> Another comment is whether the 'instanceof' code is the
> best performer for checking if the argument is a String.
> I might think that 'seq.getClass().equals(String.class)' is faster.
>
Interesting. I don't see examples of such pattern in JDK.
Anyhow, I think that the case when a StringBuilder is constructed from a
String down-cast to CharSequence should be rare in practice, so it is
sensible to keep the code more ideomatic, i.e. use instanceof.
> And in this most recent webrev that has separated the
> AbstractStringBuilder
> constructors for String from CharSequence, is it more likely that the
> argument
> will be an AbstractStringBuilder than a String so that comparison
> should be done first.
>
Yes, it's a good point! I reordered the branches in the latest webrev.
With kind regards,
Ivan
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With kind regards,
Ivan Gerasimov
