jdk8 : parallel programming made (too ?) easy
TRANSCRIPT
What did happen in 2005 ?
What did happen in 2005 ?
What did happen in 2005 ?
From 2005 till…
From 2005 till…
Java parallel toolbox
What is the Fork / Join about ?
Fork / Join caveats
Fork / Join caveats
Then comes the Parallel Arrays API
http://g.oswego.edu/dl/concurrency-interest/
Then comes the Parallel Arrays API
ForkJoinPool pool = new ForkJoinPool() ; // package !
ParralelLongArray a = ParralelLongArray.create(pool) ;
Then comes the Parallel Arrays API
Ops.LongOp add2 = new Ops.LongOp() {
@Override
public long op(long l1) {
return l1 + 2 ;
}
} ;
a2 = a.withMapping(add2) ;
Then comes the Parallel Arrays API
Ops.LongPredicate filter = new Ops.LongPredicate() {
@Override
public boolean op(long l1) {
return l1 > 50 ;
}
}
a2 = a.withFilter(filter) ;
a2.all() ;
Then comes the Parallel Arrays API
Ops.LongReducer reducer = new Ops.LongReducer() {
@Override
public long op(long l1, long l2) {
return l1 + l2 ;
}
}
long reducedValue = a.reduce(reducer, 0L) ;
JDK 6 & 7
2 tools available :
- Fork / Join
- Parallel Arrays
And then comes the JDK 8
Collection<Person> persons = ... ;
int maxAge = persons.stream().map(p -> p.getAge()).reduce(0, Math::max) ;
Collection<Person> oldies = new ArrayList<>() ;
persons.stream().filter(p -> p.age > 40).into(oldies) ;
And then comes the JDK 8
Collection<Person> persons = ... ;
int maxAge = persons.stream().parallel()
.map(p -> p.getAge()).reduce(0, Math::max) ;
Collection<Person> oldies = new ArrayList<>() ;
persons.stream().parallel().filter(p -> p.age > 40).into(oldies) ;
And then comes the JDK 8
public interface Spliterator<E> {
public Spliterator<E>[] splits() ;
public int getNaturalSplits() ;
}
http://www.parleys.com/#st=5&id=3125&sl=0
How to use all that ?
1st caveat : associativity
Associativity
Associativity
Associativity
2nd caveat : performance
long begin = System.nanoTime() ; List<String> hugeList = new ArrayList<>(N) ; // N = 16_000_000 for (int i = 0 ; i < N ; i++) { long l = random.nextLong() ; l = l > 0 ? l : -l ; hugeList.add(Long.toString(l, 32)) ; }
Sorting
Sorting performance
Sorting performance
Sorting performance
Sorting performance
Sorting performance
Sorting performance
Sorting performance
Sorting performance
Sorting performance
An even worse case
An even worse case
An even worse case
Arrays ? Going parallel is easy !
Arrays ? Going parallel is easy…
Arrays ? Going parallel is easy…
3rd caveat
3rd caveat
Conclusion
Conclusion
Conclusion
Conclusion
Conclusion
Thank you !
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