javolution.context.ConcurrentContext Class Reference

Inheritance diagram for javolution.context.ConcurrentContext:

Collaboration diagram for javolution.context.ConcurrentContext:

Public Member Functions
abstract void	execute (Runnable logic)
abstract void	setConcurrency (int concurrency)
abstract int	getConcurrency ()
void	exit ()

Static Public Member Functions
static ConcurrentContext	enter ()
static void	execute (Runnable... logics)
static AbstractContext	current ()
static< T extends AbstractContext > T	enter (Class< T > custom)
static void	inherit (AbstractContext ctx)

Static Public Attributes
static final Configurable< Integer >	CONCURRENCY

Protected Member Functions
	ConcurrentContext ()
AbstractContext	enterInner ()
AbstractContext	getOuter ()
abstract AbstractContext	inner ()

Static Protected Member Functions
static< T extends AbstractContext > T	current (Class< T > type)

Private Attributes
AbstractContext	outer

Static Private Attributes
static final ThreadLocal< AbstractContext >	CURRENT = new ThreadLocal<AbstractContext>()

Detailed Description

A context able to take advantage of concurrent algorithms on multi-processors systems.

When a thread enters a concurrent context, it may performs concurrent executions by calling the execute(Runnable) static method. The logic is then executed by a concurrent thread or by the current thread itself if there is no concurrent thread immediately available (the number of concurrent threads is limited, see CONCURRENCY). [code] ConcurrentContext ctx = ConcurrentContext.enter(); try { ctx.execute(new Runnable() {...}); ctx.execute(new Runnable() {...});
} finally { ctx.exit(); // Waits for all concurrent executions to complete. // Re-exports any exception raised during concurrent executions. }[/code]

or equivalent shorter notation: [code] ConcurrentContext.execute(new Runnable() {...}, new Runnable() {...});[/code]

Only after all concurrent executions are completed, is the current thread allowed to exit the scope of the concurrent context (internal synchronization).

Concurrent logics always execute within the same context as the calling thread.

Concurrent contexts ensure the same behavior whether or not the execution is performed by the current thread or a concurrent thread. Any error or runtime exception raised during the concurrent logic executions is propagated to the current thread.

Concurrent contexts are easy to use, and provide automatic load-balancing between processors with almost no overhead. Here is a concurrent/recursive quick/merge sort using anonymous inner classes. [code] static void concurrentSort(final FastTable<? extends Comparable> table) { final int size = table.size(); if (size < 100) { table.sort(); // Direct quick sort. } else { // Splits table in two and sort both part concurrently. final FastTable<? extends Comparable> t1 = new FastTable(); final FastTable<? extends Comparable> t2 = new FastTable(); ConcurrentContext ctx = ConcurrentContext.enter(); try { ctx.execute(new Runnable() { public void run() { t1.addAll(table.subList(0, size / 2)); concurrentSort(t1); // Recursive. } }); ctx.execute(new Runnable() { public void run() { t2.addAll(table.subList(size / 2, size)); concurrentSort(t2); // Recursive. } }); } finally { ctx.exit(); // Joins. } // Merges results. for (int i=0, i1=0, i2=0; i < size; i++) { if (i1 >= t1.size()) { table.set(i, t2.get(i2++)); } else if (i2 >= t2.size()) { table.set(i, t1.get(i1++)); } else { Comparable o1 = t1.get(i1); Comparable o2 = t2.get(i2); if (o1.compareTo(o2) < 0) { table.set(i, o1); i1++; } else { table.set(i, o2); i2++; } } } } }[/code]

Here is another example using execute(Runnable ...) static method (Karatsuba recursive multiplication for large integers). [code] public LargeInteger multiply(LargeInteger that) { if (that._size <= 1) { return multiply(that.longValue()); // Direct multiplication. } else { // Karatsuba multiplication in O(n^log2(3)) int bitLength = this.bitLength(); int n = (bitLength >> 1) + (bitLength & 1);

// this = a + 2^n b, that = c + 2^n d LargeInteger b = this.shiftRight(n); LargeInteger a = this.minus(b.shiftLeft(n)); LargeInteger d = that.shiftRight(n); LargeInteger c = that.minus(d.shiftLeft(n)); Multiply ac = new Multiply(a, c); Multiply bd = new Multiply(b, d); Multiply abcd = new Multiply(a.plus(b), c.plus(d)); ConcurrentContext.execute(ac, bd, abcd); // Convenience method.
// a*c + ((a+b)*(c+d)-a*c-b*d) 2^n + b*d 2^2n return ac.result.plus(abcd.result.minus(ac.result.plus(bd.result)).shiftWordLeft(n)) .plus(bd.result.shiftWordLeft(n << 1)); } } private static class Multiply implements Runnable { LargeInteger left, right, result; Multiply(LargeInteger left, LargeInteger right) { this.left = left; this.right = right; } public void run() { result = left.times(right); // Recursive. } }[/code]

Concurrency can be adjusted or disabled. The default concurrency is defined by the CONCURRENCY configurable. [code] ConcurrentContext ctx = ConcurrentContext.enter(); try { ctx.setConcurrency(0); // Disables concurrency runAnalysis(); // Performs analysis sequentially. } finally { ctx.exit(); // Back to previous concurrency settings.
}[/code]

Author

Jean-Marie Dautelle

Version

6.0 December 12, 2012

Definition at line 151 of file ConcurrentContext.java.

Constructor & Destructor Documentation

ConcurrentContext()

javolution.context.ConcurrentContext.ConcurrentContext ( )

protected

Default constructor.

Definition at line 181 of file ConcurrentContext.java.

{}

Member Function Documentation

current() [1/2]

static AbstractContext javolution.context.AbstractContext.current ( )

staticinherited

Returns the current context for the current thread or

null 

if this thread has no context (default).

Definition at line 61 of file AbstractContext.java.

                                            {
        return AbstractContext.CURRENT.get();
    }

References javolution.context.AbstractContext.CURRENT.

Referenced by javolution.context.LogContext.currentLogContext(), javolution.context.SecurityContext.currentSecurityContext(), javolution.text.TextContext.currentTextContext(), javolution.xml.XMLContext.currentXMLContext(), javolution.context.LocalContext.enter(), javolution.context.ConcurrentContext.enter(), and javolution.context.LocalContext.Parameter< T >.get().

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current() [2/2]

static <T extends AbstractContext> T javolution.context.AbstractContext.current ( Class< T >  type )

staticprotectedinherited

Returns the current context of specified type or

null 

if none.

Definition at line 69 of file AbstractContext.java.

                                                                          {
        AbstractContext ctx = AbstractContext.CURRENT.get();
        while (ctx != null) {
            if (type.isInstance(ctx))
                return (T) ctx;
            ctx = ctx.outer;
        }
        return null;
    }

References javolution.context.AbstractContext.CURRENT, and javolution.context.AbstractContext.outer.

enter() [1/2]

static ConcurrentContext javolution.context.ConcurrentContext.enter ( )

static

Enters and returns a new concurrent context instance.

Definition at line 186 of file ConcurrentContext.java.

                                            {
        ConcurrentContext ctx = current(ConcurrentContext.class);
        if (ctx == null) { // Root.
            ctx = OSGiServices.getConcurrentContext();
        }
        return (ConcurrentContext) ctx.enterInner();
    }

References javolution.context.AbstractContext.current(), javolution.context.AbstractContext.enterInner(), and javolution.osgi.internal.OSGiServices.getConcurrentContext().

Referenced by javolution.context.ConcurrentContext.execute(), javolution.util.internal.map.ParallelMapImpl< K, V >.perform(), javolution.util.internal.collection.ParallelCollectionImpl< E >.perform(), javolution.util.internal.map.ParallelMapImpl< K, V >.update(), and javolution.util.internal.collection.ParallelCollectionImpl< E >.update().

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enter() [2/2]

static <T extends AbstractContext> T javolution.context.AbstractContext.enter ( Class< T >  custom )

staticinherited

Enters the scope of a custom context. This method raises a SecurityException if the permission to enter contexts of the specified class is not granted. For example, the following disallow entering any custom context. [code] SecurityContext ctx = SecurityContext.enter(); try { ctx.revoke(new SecurityContext.Permission(AbstractContext.class, "enter")); ... // Cannot enter any custom context. } finally { ctx.exit(); // Back to previous security settings. }[/code]

Parameters

custom

the custom context to enter.

Exceptions

IllegalArgumentException	if the specified class default constructor cannot be instantiated.
SecurityException	if SecurityContext.Permission(custom, "enter") is not granted.

See also

SecurityContext.Permission

Definition at line 101 of file AbstractContext.java.

                                                                       {
        SecurityContext.check(new Permission<T>(custom, "enter"));
        try {
            return (T) custom.newInstance().enterInner();
        } catch (InstantiationException e) {
            throw new IllegalArgumentException(
                    "Cannot instantiate instance of " + custom, e);
        } catch (IllegalAccessException e) {
            throw new IllegalArgumentException("Cannot access " + custom, e);
        }
    }

References javolution.context.SecurityContext.check().

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enterInner()

AbstractContext javolution.context.AbstractContext.enterInner ( )

protectedinherited

Enters the scope of an inner context which becomes the current context; the previous current context becomes the outer of this context.

Returns

the inner context entered.

Definition at line 141 of file AbstractContext.java.

                                           {
        AbstractContext inner = inner();
        inner.outer = AbstractContext.CURRENT.get();
        AbstractContext.CURRENT.set(inner);
        return inner;
    }

References javolution.context.AbstractContext.CURRENT, and javolution.context.AbstractContext.outer.

Referenced by javolution.xml.XMLContext.enter(), javolution.text.TextContext.enter(), javolution.context.LogContext.enter(), javolution.context.LocalContext.enter(), javolution.context.SecurityContext.enter(), and javolution.context.ConcurrentContext.enter().

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execute() [1/2]

abstract void javolution.context.ConcurrentContext.execute ( Runnable  logic )

abstract

Executes the specified logic by a concurrent thread if one available; otherwise the logic is executed by the current thread. Any exception or error occurring during the concurrent execution is propagated to the current thread upon exit of the concurrent context.

Parameters

logic

the logic to be executed concurrently when possible.

Reimplemented in javolution.context.internal.ConcurrentContextImpl.

execute() [2/2]

static void javolution.context.ConcurrentContext.execute ( Runnable...  logics )

static

Convenience method to executes the specified logics concurrently. This method is equivalent to: [code] ConcurrentContext ctx = ConcurrentContext.enter(); try { ctx.execute(logics[0]); ctx.execute(logics[1]); ... } finally { ctx.exit(); }[/code]

Parameters

logics

the logics to execute concurrently if possible.

Definition at line 209 of file ConcurrentContext.java.

                                                   {
        ConcurrentContext ctx = ConcurrentContext.enter();
        try {
            for (Runnable logic : logics) {
                ctx.execute(logic);
            }
        } finally {
            ctx.exit();
        }
    }

References javolution.context.ConcurrentContext.enter(), javolution.context.ConcurrentContext.execute(), and javolution.context.ConcurrentContext.exit().

Referenced by javolution.context.ConcurrentContext.execute(), javolution.util.internal.map.ParallelMapImpl< K, V >.perform(), javolution.util.internal.collection.ParallelCollectionImpl< E >.perform(), javolution.util.internal.map.ParallelMapImpl< K, V >.update(), and javolution.util.internal.collection.ParallelCollectionImpl< E >.update().

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exit()

void javolution.context.ConcurrentContext.exit

(

)

Exits the scope of this concurrent context; this method blocks until all the concurrent executions are completed.

Exceptions

RuntimeException	re-exports any exception raised during concurrent executions.
Error	re-exports any error raised during concurrent executions.
IllegalStateException	if this context is not the current context.

Reimplemented from javolution.context.AbstractContext.

Reimplemented in javolution.context.internal.ConcurrentContextImpl.

Definition at line 255 of file ConcurrentContext.java.

                       { // Redefine here for documentation purpose.
        super.exit();
    }

Referenced by javolution.context.ConcurrentContext.execute(), javolution.util.internal.map.ParallelMapImpl< K, V >.perform(), javolution.util.internal.collection.ParallelCollectionImpl< E >.perform(), javolution.util.internal.map.ParallelMapImpl< K, V >.update(), and javolution.util.internal.collection.ParallelCollectionImpl< E >.update().

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getConcurrency()

abstract int javolution.context.ConcurrentContext.getConcurrency ( )

abstract

Returns the current concurrency which is basically the number of concurrent threads authorized to do concurrent work (on top of all others threads of course).

Reimplemented in javolution.context.internal.ConcurrentContextImpl.

Referenced by javolution.util.internal.map.ParallelMapImpl< K, V >.perform(), javolution.util.internal.collection.ParallelCollectionImpl< E >.perform(), javolution.util.internal.map.ParallelMapImpl< K, V >.update(), and javolution.util.internal.collection.ParallelCollectionImpl< E >.update().

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getOuter()

AbstractContext javolution.context.AbstractContext.getOuter ( )

protectedinherited

Returns the outer context of this context or

null 

if this context has no outer context.

Definition at line 167 of file AbstractContext.java.

                                         {
        return outer;
    }

inherit()

static void javolution.context.AbstractContext.inherit ( AbstractContext  ctx )

staticinherited

Inherits the specified context which becomes the context of the current thread. This method is particularly useful when creating new threads to make them inherits from the context stack of the parent thread. [code] //Spawns a new thread inheriting the context of the current thread. MyThread myThread = new MyThread(); myThread.inherited = AbstractContext.current(); myThread.start(); ... class MyThread extends Thread { AbstractContext inherited; public void run() { AbstractContext.inherit(inherited); // Sets current context. ... } }[/code]

Definition at line 131 of file AbstractContext.java.

                                                    {
        CURRENT.set(ctx);
    }

Referenced by javolution.context.internal.ConcurrentThreadImpl.run().

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inner()

abstract AbstractContext javolution.context.AbstractContext.inner ( )

abstractprotectedinherited

Returns a new inner instance of this context inheriting the properties of this context. The new instance can be configured independently from its parent.

Reimplemented in javolution.context.internal.ConcurrentContextImpl, javolution.text.internal.TextContextImpl, javolution.context.internal.LogContextImpl, javolution.context.internal.SecurityContextImpl, javolution.xml.internal.XMLContextImpl, and javolution.context.internal.LocalContextImpl.

setConcurrency()

abstract void javolution.context.ConcurrentContext.setConcurrency ( int  concurrency )

abstract

Sets the maximum concurrency. Setting a value greater than the current concurrency has no effect (concurrency can only be reduced).

Reimplemented in javolution.context.internal.ConcurrentContextImpl.

Member Data Documentation

CONCURRENCY

final Configurable<Integer> javolution.context.ConcurrentContext.CONCURRENCY

static

Initial value:

= new Configurable<Integer>() {
        @Override
        protected Integer getDefault() {
            return Runtime.getRuntime().availableProcessors() - 1;
        }
 
        @Override
        protected Integer initialized(Integer value) {
            return MathLib.min(value, 65536); 
        }
 
        @Override
        protected Integer reconfigured(Integer oldCount, Integer newCount) {
            throw new UnsupportedOperationException(
                    "Concurrency reconfiguration not supported.");
        }
    }

Holds the maximum concurrency
(default Runtime.getRuntime().availableProcessors() - 1). The maximum concurrency is configurable. For example, the JVM option

-Djavolution.context.ConcurrentContext#CONCURRENCY=0 

disables concurrency.

Definition at line 160 of file ConcurrentContext.java.

Referenced by javolution.context.internal.ConcurrentContextImpl.ConcurrentContextImpl().

CURRENT

final ThreadLocal<AbstractContext> javolution.context.AbstractContext.CURRENT = new ThreadLocal<AbstractContext>()

staticprivateinherited

Holds the last context entered (thread-local).

Definition at line 45 of file AbstractContext.java.

Referenced by javolution.context.AbstractContext.current(), javolution.context.AbstractContext.enterInner(), and javolution.context.AbstractContext.exit().

outer

AbstractContext javolution.context.AbstractContext.outer

privateinherited

Holds the outer context or

null 

if none (top context).

Definition at line 50 of file AbstractContext.java.

Referenced by javolution.context.AbstractContext.current(), and javolution.context.AbstractContext.enterInner().

---

The documentation for this class was generated from the following file:

• ConcurrentContext.java