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Re: Easy exhaustive search with Java 8 Streams

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Am 28.04.2015 12:35, schrieb Jan Burse:
> Hi,
>
> How fast is this? Any figures?
>
> Bye
>

I did a simple micro-benchmark with JMH 1.9.1 (available from Maven 
Central) on my laptop computer, which is a quad-core machine with an 
Intel i7 processor.

Here are the measurement parameters:

# JMH 1.9.1 (released 5 days ago)
# VM invoker: C:\Program Files\Java\jdk1.8.0_25\jre\bin\java.exe
# VM options: -Dfile.encoding=UTF-8
# Warmup: 5 iterations, 1 s each
# Measurement: 25 iterations, 1 s each
# Timeout: 10 min per iteration
# Threads: 1 thread, will synchronize iterations
# Benchmark mode: Average time, time/op

I measured the flatMap solution against the equivalent formulation with 
eight nested for-loops. The flatMap solution is about half as fast. 
Here's a representative measurement:


Benchmark                        Mode  Cnt    Score   Error  Units
measureFlatMpSearchPerformance   avgt   25  662.377 ± 3.747  ms/op
measureForLoopSearchPerformance  avgt   25  316.105 ± 3.823  ms/op


The nice thing abbout Streams is they are so easily parallelizable.
Just throw in a ".parallel()" in the first line like this:

    remove(DIGITS, 0).stream().parallel().flatMap( s ->

leaving everything else unchanged, and the (parallel) flatMap version 
becomes twice as fast as the (serial) for-loop version:


Benchmark                        Mode  Cnt    Score   Error  Units
measureFlatMpSearchPerformance   avgt   25  168.278 ± 1.700  ms/op
measureForLoopSearchPerformance  avgt   25  315.806 ± 2.878  ms/op


The effectiveness of parallelization of course depends on the 
problem-specific properties of your search space.

-- Sebastian

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Thread

Easy exhaustive search with Java 8 Streams Sebastian <news@seyweiler.dyndns.org> - 2015-04-27 20:32 +0200
  Re: Easy exhaustive search with Java 8 Streams Jan Burse <janburse@fastmail.fm> - 2015-04-28 12:35 +0200
    Re: Easy exhaustive search with Java 8 Streams Sebastian <news@seyweiler.dyndns.org> - 2015-04-29 11:12 +0200
      Re: Easy exhaustive search with Java 8 Streams j4n bur53 <janburse@fastmail.fm> - 2015-04-30 09:02 +0200
  Re: Easy exhaustive search with Java 8 Streams Sebastian <news@seyweiler.dyndns.org> - 2015-04-29 09:45 +0200

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