Philippe Marschall created LANG-1229:
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Summary: Performance regression due to cyclic hashCode guard
Key: LANG-1229
URL: https://issues.apache.org/jira/browse/LANG-1229
Project: Commons Lang
Issue Type: Bug
Components: lang.builder.*
Affects Versions: 3.5
Reporter: Philippe Marschall
We observed a severe performance regression in HashCodeBuilder in 3.5 trunk
compared to 3.4 release. We get about 20% of the throughput in 3.5 trunk for
common cases compared to 3.4 release. Previously there was no noticeable
overhead of using HashCodeBuilder. Investigating we found the performance
degradation was caused by the fix for LANG-456. It causes the method to be too
large to be inlined and escape analysis to fail (see LANG-1218 for a related
discussion).
We currently do not see a way to keep the 3.4 performance and support cyclic
graphs. The append methods have not supported cycles for so long we feel it's
de facto part of the contract by now. Since neither the JDK nor the Guava
hashCode helper methods support cyclic graphs we don't believe this is an
unreasonable assumption. In addition EqualsBuilder#append(Object,Object)
doesn't support cycles.
If supporting cycles is a requirement we propose the introduction of new
#appendRecursive (or named differently) methods to both HashCodeBuilder and
EqualsBuilder that add cycle guards. If that is an acceptable compromise we
would be willing to provide patches.
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