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From "Shapira, Yoav" <Yoav.Shap...@mpi.com>
Subject RE: [COLLECTIONS] FastHashMap performance
Date Tue, 03 Jun 2003 19:05:40 GMT

Howdy,
I've had tests with both a normal hashmap (just new HashMap() used) and
a synchronized wrapper (Collections.synchronizedMap(new HashMap()).  I
would expect the normal HashMap to be faster than both the FastHashMap
and the synchronized HashMap.  Is my expectation wrong?

However, here are the results:
[MapTest: FastHashMap: false / Synchronized wrapper: false / Insert
time: 1592 / Read time: 30]
[MapTest: FastHashMap: true / Synchronized wrapper: false / Insert time:
1265 / Read time: 6]
[MapTest: FastHashMap: false / Synchronized wrapper: true / Insert time:
983 / Read time: 7]
[MapTest: FastHashMap: false / Synchronized wrapper: false / Insert
time: 1158 / Read time: 2]
[MapTest: FastHashMap: true / Synchronized wrapper: false / Insert time:
1194 / Read time: 2]
[MapTest: FastHashMap: false / Synchronized wrapper: true / Insert time:
827 / Read time: 2]
[MapTest: FastHashMap: false / Synchronized wrapper: false / Insert
time: 990 / Read time: 2]
[MapTest: FastHashMap: true / Synchronized wrapper: false / Insert time:
1006 / Read time: 2]
[MapTest: FastHashMap: false / Synchronized wrapper: true / Insert time:
732 / Read time: 2]
[MapTest: FastHashMap: false / Synchronized wrapper: false / Insert
time: 949 / Read time: 3]
[MapTest: FastHashMap: true / Synchronized wrapper: false / Insert time:
1003 / Read time: 2]
[MapTest: FastHashMap: false / Synchronized wrapper: true / Insert time:
1579 / Read time: 2]
[MapTest: FastHashMap: false / Synchronized wrapper: false / Insert
time: 888 / Read time: 2]
[MapTest: FastHashMap: true / Synchronized wrapper: false / Insert time:
1045 / Read time: 2]
[MapTest: FastHashMap: false / Synchronized wrapper: true / Insert time:
793 / Read time: 2]
[MapTest: FastHashMap: false / Synchronized wrapper: false / Insert
time: 1151 / Read time: 2]
[MapTest: FastHashMap: true / Synchronized wrapper: false / Insert time:
855 / Read time: 2]
[MapTest: FastHashMap: false / Synchronized wrapper: true / Insert time:
905 / Read time: 3]
[MapTest: FastHashMap: false / Synchronized wrapper: false / Insert
time: 1217 / Read time: 1]
[MapTest: FastHashMap: true / Synchronized wrapper: false / Insert time:
1269 / Read time: 2]
[MapTest: FastHashMap: false / Synchronized wrapper: true / Insert time:
1107 / Read time: 2]
[MapTest: FastHashMap: false / Synchronized wrapper: false / Insert
time: 1062 / Read time: 2]
[MapTest: FastHashMap: true / Synchronized wrapper: false / Insert time:
1252 / Read time: 2]
[MapTest: FastHashMap: false / Synchronized wrapper: true / Insert time:
971 / Read time: 2]
[MapTest: FastHashMap: false / Synchronized wrapper: false / Insert
time: 1460 / Read time: 2]
[MapTest: FastHashMap: true / Synchronized wrapper: false / Insert time:
1404 / Read time: 2]
[MapTest: FastHashMap: false / Synchronized wrapper: true / Insert time:
1110 / Read time: 2]
[MapTest: FastHashMap: false / Synchronized wrapper: false / Insert
time: 1278 / Read time: 2]
[MapTest: FastHashMap: true / Synchronized wrapper: false / Insert time:
1193 / Read time: 2]
[MapTest: FastHashMap: false / Synchronized wrapper: true / Insert time:
1096 / Read time: 2]

Yoav Shapira
Millennium ChemInformatics


>-----Original Message-----
>From: ericpabst@discoverfinancial.com
>[mailto:ericpabst@discoverfinancial.com]
>Sent: Tuesday, June 03, 2003 2:58 PM
>To: Jakarta Commons Developers List
>Subject: RE: [COLLECTIONS] FastHashMap performance
>
>
>In your test, are you synchronizing the HashMap?  FastHashMap
implements
>smart synchronization.  It should not be compared with an
unsynchronized
>version of HashMap.
>
>P.S.  In fact, it might be nice to allow doing this smart
synchronization
>on *any* Map.  i.e. alternative to Collections.synchronizeMap(Map).
>
>Eric Pabst
>Discover Financial Services
>2500 Lake Park Blvd., 3N
>West Valley City, UT 84120
>Ph: 801.902.4636
>Fax: 801.902.4123
>
>
>
>|---------+--------------------------->
>|         |           "Shapira, Yoav" |
>|         |           <Yoav.Shapira@mp|
>|         |           i.com>          |
>|         |                           |
>|         |           06/03/03 12:54  |
>|         |           PM              |
>|         |           Please respond  |
>|         |           to "Jakarta     |
>|         |           Commons         |
>|         |           Developers List"|
>|         |                           |
>|---------+--------------------------->
>
>-----------------------------------------------------------------------
-
>---------------------------------------|
>  |
>|
>  |        To:      "Jakarta Commons Developers List" <commons-
>dev@jakarta.apache.org>                            |
>  |        cc:
>|
>  |        Subject: RE: [COLLECTIONS] FastHashMap performance
>|
>
>-----------------------------------------------------------------------
-
>---------------------------------------|
>
>
>
>
>
>Howdy,
>I understand it's just a wrapper, and that the
>reading cannot be any faster.  I'm curious why the
>writing is so much faster, even in the default (not fast)
>mode of FastHashMap.
>
>Yoav Shapira
>Millennium ChemInformatics
>
>
>>-----Original Message-----
>>From: Juozas Baliuka [mailto:baliuka@centras.lt]
>>Sent: Tuesday, June 03, 2003 2:36 PM
>>To: Jakarta Commons Developers List
>>Subject: Re: [COLLECTIONS] FastHashMap performance
>>
>>FastHashMap can not be faster than HasMap in single thread just
because
>it
>>uses HasMap to implement mappings:
>>
>> public Object get(Object key) {
>>        if (fast) {
>>            return (map.get(key));
>>        } else {
>>            synchronized (map) {
>>                return (map.get(key));
>>            }
>>        }
>>    }
>>
>>
>>/**
>>     * Construct an empty map.
>>     */
>>    public FastHashMap() {
>>        super();
>>        this.map = new HashMap();
>>    }
>>
>>----- Original Message -----
>>From: "Shapira, Yoav" <Yoav.Shapira@mpi.com>
>>To: "Jakarta Commons Developers List" <commons-dev@jakarta.apache.org>
>>Sent: Tuesday, June 03, 2003 8:00 PM
>>Subject: RE: [COLLECTIONS] FastHashMap performance
>>
>>
>>Howdy,
>>Neither did I, but I just ran the attached benchmark and got
surprising
>>results.  I hope the attachement comes through OK: if not I'll re-post
>>inline.  This benchmark has just one thread writing, one thread
>reading,
>>which I expected to be the case where FastHashMap is not as efficient
>as
>>HashMap.
>>
>>The benchmark inserts 100000 records in the map, then reads 1000 of
>>those at random.  I run this 10 times for each map implemention.  I'm
>>ignoring the first run read times as there's overhead in initializing
>>the Random generator.
>>
>>I'm running this test on JDK 1.4.1, no special java switches, just
java
>>MapTest on the command line, on Solaris 8.
>>
>>I'm very curious to hear comments, ideas.  I was expecting to have to
>>write another test with multiple writing threads, but if FastHashMap
is
>>faster even for the simple case, why ever use the regular HashMap?
>>
>>The results are:
>>[MapTest: Map class: java.util.HashMap / Insert time: 1616 / Read
time:
>>30]
>>[MapTest: Map class: org.apache.commons.collections.FastHashMap /
>Insert
>>time: 1252 / Read time: 6]
>>[MapTest: Map class: java.util.HashMap / Insert time: 958 / Read time:
>>2]
>>[MapTest: Map class: org.apache.commons.collections.FastHashMap /
>Insert
>>time: 1203 / Read time: 2]
>>[MapTest: Map class: java.util.HashMap / Insert time: 820 / Read time:
>>2]
>>[MapTest: Map class: org.apache.commons.collections.FastHashMap /
>Insert
>>time: 988 / Read time: 2]
>>[MapTest: Map class: java.util.HashMap / Insert time: 781 / Read time:
>>2]
>>[MapTest: Map class: org.apache.commons.collections.FastHashMap /
>Insert
>>time: 1033 / Read time: 3]
>>[MapTest: Map class: java.util.HashMap / Insert time: 720 / Read time:
>>2]
>>[MapTest: Map class: org.apache.commons.collections.FastHashMap /
>Insert
>>time: 1067 / Read time: 2]
>>[MapTest: Map class: java.util.HashMap / Insert time: 1454 / Read
time:
>>2]
>>[MapTest: Map class: org.apache.commons.collections.FastHashMap /
>Insert
>>time: 1267 / Read time: 2]
>>[MapTest: Map class: java.util.HashMap / Insert time: 1534 / Read
time:
>>2]
>>[MapTest: Map class: org.apache.commons.collections.FastHashMap /
>Insert
>>time: 862 / Read time: 2]
>>[MapTest: Map class: java.util.HashMap / Insert time: 1433 / Read
time:
>>2]
>>[MapTest: Map class: org.apache.commons.collections.FastHashMap /
>Insert
>>time: 844 / Read time: 2]
>>[MapTest: Map class: java.util.HashMap / Insert time: 1578 / Read
time:
>>2]
>>[MapTest: Map class: org.apache.commons.collections.FastHashMap /
>Insert
>>time: 1488 / Read time: 2]
>>[MapTest: Map class: java.util.HashMap / Insert time: 1450 / Read
time:
>>2]
>>[MapTest: Map class: org.apache.commons.collections.FastHashMap /
>Insert
>>time: 859 / Read time: 2]
>>
>>Yoav Shapira
>>Millennium ChemInformatics
>>
>>
>>>-----Original Message-----
>>>From: Juozas Baliuka [mailto:baliuka@centras.lt]
>>>Sent: Tuesday, June 03, 2003 1:53 PM
>>>To: Jakarta Commons Developers List
>>>Subject: Re: [COLLECTIONS] FastHashMap performance
>>>
>>>I do not think it is faster than java.util.HashMap, it is just pseudo
>>>thread
>>>safe wrapper.
>>>
>>>----- Original Message -----
>>>From: "Shapira, Yoav" <Yoav.Shapira@mpi.com>
>>>To: <commons-dev@jakarta.apache.org>
>>>Sent: Tuesday, June 03, 2003 7:17 PM
>>>Subject: [COLLECTIONS] FastHashMap performance
>>>
>>>
>>>
>>>Howdy,
>>>Has anyone benchmarked the performance of the FastHashMap and how it
>>>compares to the java.util.HashMap implementation?  If so, are the
>>>benchmarks available online somewhere?
>>>
>>>I don't doubt its quality nor its performance, just curious...
Thanks,
>>>
>>>Yoav Shapira
>>>Millennium ChemInformatics
>>>
>>>
>>>
>>>
>>>
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>>
>>
>>
>>This e-mail, including any attachments, is a confidential business
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>>and/or privileged.  This e-mail is intended only for the individual(s)
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>
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intended
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This e-mail, including any attachments, is a confidential business communication, and may
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