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From "Vladimir Strigun" <vstri...@gmail.com>
Subject Re: [classlib][java.math]performance improvement for java.math package
Date Tue, 20 Jun 2006 08:21:31 GMT
Hi Daniel,

Thank you for your response and sorry for delay with my answer. Please
find my comments inside.

On 6/15/06, Daniel Fridlender <dfridlender@gmail.com> wrote:
> Hi Vladimir,
>
> thank you very much for this new optimization of math from, as you
> said, enterprise-level applications point of view.  Of course we are
> considering this optimization (H551) as well for the combination of
> the different math implementations into a new and more efficient one.
>
> In fact we are already working on a new version combining H39+380 with
> H199 and are introducing some of H551 optimizations as well.  On the
> other hand, we are for the moment postponing some other of your
> optimizations for a future version since introducing them now would
> break, in my opinion prematurely, a nice design property we have so
> far: BigDecimal depends only on public features of BigInteger.

Thanks for doing this. What kind of optimization you planned to add first?
I can agree that it's good to have such design, but nevertheless since
BigDecimal internally represented though BigInteger, possibly it
should be also good to use some non public features of BigInteger.

> So, we are following this plan:
>
> 1) integration of H39+H380 with H199 and with part of H551
> 2) optimization of this with more advanced algorithms
> 3) introducing remaining optimization from H551
>
> For the point 2) above I would still like to have independence between
> BigDecimal and BigInteger.
>
> I hope you agree with this plan.

Yes, this plan sounds good for me. Let's follow it and compare
implementations after 1st integration. We can use microbench that
attached to the issue, or, possibly we should find another benchmark
for it. What benchmarks you have used for performance measurement?

> I would also be grateful if you could be more specific when you
> mention enterprise-level applications.  We are looking for realistic
> applications of math in order to be able to get an idea of how the
> implementations will work in practice.  So far we had only found a few
> applications in cryptography and in number factorization (actually,
> they are applications of BigInteger only).  Could you point me to the
> applications you had in mind so that we can add them to our (so far)
> small collection of applications?  Are those applications for which
> float or double are not enough?

I have in mind some banking software, online payment processing, etc.
Within these type of application values usually fit to 32 bit, that's
why we have special case for small numbers. Also, these optimizations
do not degrade in common.

Thanks,
Vladimir.

> Thanks again,
>
> Daniel
>
>
> On 6/2/06, Vladimir Strigun <vstrigun@gmail.com> wrote:
> > Our team has done some analysis of current Harmony implementation of
> > java.math package. The implementation was considered from the
> > performance point of view and I'd like to share results of our work
> > with you.
> >
> > The analysis and tuning was made from the enterprise-level
> > applications point of view which are known to use BigInteger and
> > BigDecimal for storing numeric information. In most cases the numbers
> > there fit well within 32 bits. So coming from the BigDecimal
> > perspective which is really important for these applications and
> > taking into account some specifics (small numbers) we made some
> > optimizations in both BigDecimal and BigInteger. The latter was tuned
> > specifically for BigDecimal:
> >
> > - Special handling for small numbers (fit within 32 bit) was added to
> > all methods
> > - Frequently used constants (0..10) were cached and reused by valueOf
> > method (no need to create a new instance of BigInteger)
> > - as well as were powers of 10 (0..10)
> > - methods add(), divide(), divideAndRemainer() in BigInteger were
> > optimized for short values if both arguments can fit in 32 bits the
> > resulting BigInteger is created  by valueOf method.
> >
> >
> > If we consider enterprise level applications, we can imagine that
> > toString() method is also frequently used. The method was analyzed and
> > as a result we combined toString() methods in BigDecimal and
> > BigInteger to one unified method in BigInteger. Method
> > BigInteger.toDecimalScaledString(int scale) now  is used from  both
> > BigInteger and BigDecimal.  This way allows reducing amount of created
> > objects and data copying. In addition, size calculation was modified
> > for resulting array. In the new implementation the size is calculated
> > with less precision. Because allocated char array will be copied into
> > String and collected by GC after toString() then it is not a problem
> > if the allocated char array will be slightly bigger then necessary.
> >
> > I've attached the changes we made for BigInteger and BigDecimal to Harmony-551
> >
> > We also have created a set of micro benchmarks (which I'll to attach
> > to JIRA as well) which shows that our special-case handling doesn't
> > break the performance for other cases and we do not degrade in common,
> > and, of course, all unit tests pass with new version. Below you can
> > find several comparisons in performance between current version and
> > the fixed one.
> >
> > ===
> >
> > Ops/sec for toString() method of BigDecimal
> >
> > Number     Current       fixed one
> > of digits     version
> > 2       1121    5354
> > 4       774     7514
> > 8       615     6748
> > 12      743     5543
> > 16      623     4494
> > 24      389     4895
> > 32      306     3496
> > 48      232     5815
> > 64      224     3761
> > 128     91      87
> >
> > Ops/sec for divide method of BigInteger
> >
> > Number     Current       fixed one
> > of digits     version
> >
> > 2       5247    6315
> > 4       4623    6497
> > 8       5560    7491
> > 12      838     838
> > 16      2533    2063
> > 24      1689    1717
> > 32      2397    2494
> > 48      2143    2131
> > 64      613     525
> > 128     1399    1418
> >
> > Ops/sec for subtract method of BigInteger
> >
> > Number     Current       fixed one
> > of digits     version
> >
> > 2       3920    4394
> > 4       3300    3302
> > 8       5178    5640
> > 12      957     913
> > 16      3794    2904
> > 24      2057    1962
> > 32      3421    3241
> > 48      3469    2828
> > 64      652     610
> > 128     2318    2246
> >
> > ===
> >
> > Unfortunately we haven't look thoroughly to ITC contribution, so it
> > may happen that some of the optimizations described in this letter
> > were already implemented there. Daniel, could you please consider our
> > new implementation when you start to merge implementations math
> > packages. If optimization methods described above already have been
> > implemented in ITC contribution it will be great to compare internal
> > representation of BigInteger and try to measure affect of different
> > approaches.
> >
> >
> >
> >
> > On 6/2/06, Vladimir Strigun (JIRA) <jira@apache.org> wrote:
> > >     [ http://issues.apache.org/jira/browse/HARMONY-551?page=all ]
> > >
> > > Vladimir Strigun updated HARMONY-551:
> > > -------------------------------------
> > >
> > >    Attachment: Harmony-551.diffs
> > >
> > > Please try my patch.
> > > Several features were added:
> > > - special handling for small value
> > > - frequently used constans were cached
> > > - several methods were modified and optimized for small value.
> > > etc.
> > >
> > > > [classlib][java.math] performance improvement for java.math package
> > > > -------------------------------------------------------------------
> > > >
> > > >          Key: HARMONY-551
> > > >          URL: http://issues.apache.org/jira/browse/HARMONY-551
> > > >      Project: Harmony
> > > >         Type: Improvement
> > >
> > > >   Components: Classlib
> > > >     Reporter: Vladimir Strigun
> > > >  Attachments: Harmony-551.diffs
> > > >
> > > > Performance improvement for BigDecimal and BigInteger classes.
> > > > I will attach patch soon.
> > >
> > > --
> > > This message is automatically generated by JIRA.
> > > -
> > > If you think it was sent incorrectly contact one of the administrators:
> > >   http://issues.apache.org/jira/secure/Administrators.jspa
> > > -
> > > For more information on JIRA, see:
> > >   http://www.atlassian.com/software/jira
> > >
> > >
> >
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