RFR 8196740 : Character.digit(int,int) returns wrong value for out of range radix
Ivan Gerasimov
ivan.gerasimov at oracle.com
Sat Feb 3 06:51:29 UTC 2018
After some experimentation, I couldn't find anything faster than the
variant with the check (value >= 0), so let's go ahead with it.
Here's the updated webrev:
http://cr.openjdk.java.net/~igerasim/8196740/01/webrev/
With kind regards,
Ivan
On 2/2/18 5:47 PM, Claes Redestad wrote:
> Hi Ivan,
>
> On 2018-02-03 02:14, Ivan Gerasimov wrote:
>> Would you please help review the fix?
>>
>> BUGURL: https://bugs.openjdk.java.net/browse/JDK-8196740
>> WEBREV: http://cr.openjdk.java.net/~igerasim/8196740/00/webrev/
>
> yes, an obvious error in hindsight!
>
>>
>>
>> I suspect that this version may even work a tiny bit faster, as we
>> perform less comparisons in a common case.
>
> Counter-intuitively it actually seems the compiler generates faster
> code in the end when keeping the
> value >= 0 test around.
>
> Your version:
>
> Benchmark Mode Cnt Score Error Units
> UUIDBenchmark.benchmarkUUIDFromString avgt 4 0.326 ± 0.017 us/op
> UUIDBenchmark.benchmarkUUIDFromString:branches avgt 289.750
> #/op
> UUIDBenchmark.benchmarkUUIDFromString:cycles avgt 1044.087 #/op
>
> With:
> int value = DIGITS[ch];
> return (value >= 0 && value < radix && radix >=
> Character.MIN_RADIX
> && radix <= Character.MAX_RADIX) ? value : -1;
>
> Benchmark Mode Cnt Score Error Units
> UUIDBenchmark.benchmarkUUIDFromString avgt 4 0.310 ± 0.018 us/op
> UUIDBenchmark.benchmarkUUIDFromString:branches avgt 256.489
> #/op
> UUIDBenchmark.benchmarkUUIDFromString:cycles avgt 988.998 #/op
>
> /Claes
>
--
With kind regards,
Ivan Gerasimov
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