Merge branch 'master' of https://github.com/eugenp/tutorials
This commit is contained in:
Loredana
commit
7a2db4f674
|
|
@ -1,12 +1,15 @@
|
|||
package com.baeldung.modules.main;
|
||||
|
||||
import com.baeldung.modules.hello.HelloInterface;
|
||||
import com.baeldung.modules.hello.HelloModules;
|
||||
import java.util.ServiceLoader;
|
||||
|
||||
public class MainApp {
|
||||
public static void main(String[] args) {
|
||||
HelloModules.doSomething();
|
||||
|
||||
HelloModules module = new HelloModules();
|
||||
module.sayHello();
|
||||
|
||||
Iterable<HelloInterface> services = ServiceLoader.load(HelloInterface.class);
|
||||
HelloInterface service = services.iterator().next();
|
||||
service.sayHello();
|
||||
}
|
||||
}
|
||||
|
|
|
|||
|
|
@ -0,0 +1,22 @@
|
|||
package com.baeldung.falsesharing;
|
||||
|
||||
import org.openjdk.jmh.annotations.Benchmark;
|
||||
import org.openjdk.jmh.annotations.Scope;
|
||||
import org.openjdk.jmh.annotations.State;
|
||||
|
||||
@State(Scope.Benchmark)
|
||||
public class FalseSharing {
|
||||
|
||||
private java.util.concurrent.atomic.LongAdder builtin = new java.util.concurrent.atomic.LongAdder();
|
||||
private LongAdder custom = new LongAdder();
|
||||
|
||||
@Benchmark
|
||||
public void builtin() {
|
||||
builtin.increment();
|
||||
}
|
||||
|
||||
@Benchmark
|
||||
public void custom() {
|
||||
custom.increment();
|
||||
}
|
||||
}
|
||||
|
|
@ -0,0 +1,237 @@
|
|||
package com.baeldung.falsesharing;
|
||||
|
||||
import java.io.Serializable;
|
||||
import java.util.concurrent.atomic.AtomicLong;
|
||||
|
||||
/**
|
||||
* Copy-pasted from {@link java.util.concurrent.atomic.LongAdder}
|
||||
*
|
||||
* One or more variables that together maintain an initially zero
|
||||
* {@code long} sum. When updates (method {@link #add}) are contended
|
||||
* across threads, the set of variables may grow dynamically to reduce
|
||||
* contention. Method {@link #sum} (or, equivalently, {@link
|
||||
* #longValue}) returns the current total combined across the
|
||||
* variables maintaining the sum.
|
||||
*
|
||||
* <p>This class is usually preferable to {@link AtomicLong} when
|
||||
* multiple threads update a common sum that is used for purposes such
|
||||
* as collecting statistics, not for fine-grained synchronization
|
||||
* control. Under low update contention, the two classes have similar
|
||||
* characteristics. But under high contention, expected throughput of
|
||||
* this class is significantly higher, at the expense of higher space
|
||||
* consumption.
|
||||
*
|
||||
* <p>LongAdders can be used with a {@link
|
||||
* java.util.concurrent.ConcurrentHashMap} to maintain a scalable
|
||||
* frequency map (a form of histogram or multiset). For example, to
|
||||
* add a count to a {@code ConcurrentHashMap<String,LongAdder> freqs},
|
||||
* initializing if not already present, you can use {@code
|
||||
* freqs.computeIfAbsent(k -> new LongAdder()).increment();}
|
||||
*
|
||||
* <p>This class extends {@link Number}, but does <em>not</em> define
|
||||
* methods such as {@code equals}, {@code hashCode} and {@code
|
||||
* compareTo} because instances are expected to be mutated, and so are
|
||||
* not useful as collection keys.
|
||||
*
|
||||
* @since 1.8
|
||||
* @author Doug Lea
|
||||
*/
|
||||
public class LongAdder extends Striped64 implements Serializable {
|
||||
private static final long serialVersionUID = 7249069246863182397L;
|
||||
|
||||
/**
|
||||
* Creates a new adder with initial sum of zero.
|
||||
*/
|
||||
public LongAdder() {
|
||||
}
|
||||
|
||||
/**
|
||||
* Adds the given value.
|
||||
*
|
||||
* @param x the value to add
|
||||
*/
|
||||
public void add(long x) {
|
||||
Cell[] as; long b, v; int m; Cell a;
|
||||
if ((as = cells) != null || !casBase(b = base, b + x)) {
|
||||
boolean uncontended = true;
|
||||
if (as == null || (m = as.length - 1) < 0 ||
|
||||
(a = as[getProbe() & m]) == null ||
|
||||
!(uncontended = a.cas(v = a.value, v + x)))
|
||||
longAccumulate(x, null, uncontended);
|
||||
}
|
||||
}
|
||||
|
||||
/**
|
||||
* Equivalent to {@code add(1)}.
|
||||
*/
|
||||
public void increment() {
|
||||
add(1L);
|
||||
}
|
||||
|
||||
/**
|
||||
* Equivalent to {@code add(-1)}.
|
||||
*/
|
||||
public void decrement() {
|
||||
add(-1L);
|
||||
}
|
||||
|
||||
/**
|
||||
* Returns the current sum. The returned value is <em>NOT</em> an
|
||||
* atomic snapshot; invocation in the absence of concurrent
|
||||
* updates returns an accurate result, but concurrent updates that
|
||||
* occur while the sum is being calculated might not be
|
||||
* incorporated.
|
||||
*
|
||||
* @return the sum
|
||||
*/
|
||||
public long sum() {
|
||||
Cell[] as = cells; Cell a;
|
||||
long sum = base;
|
||||
if (as != null) {
|
||||
for (int i = 0; i < as.length; ++i) {
|
||||
if ((a = as[i]) != null)
|
||||
sum += a.value;
|
||||
}
|
||||
}
|
||||
return sum;
|
||||
}
|
||||
|
||||
/**
|
||||
* Resets variables maintaining the sum to zero. This method may
|
||||
* be a useful alternative to creating a new adder, but is only
|
||||
* effective if there are no concurrent updates. Because this
|
||||
* method is intrinsically racy, it should only be used when it is
|
||||
* known that no threads are concurrently updating.
|
||||
*/
|
||||
public void reset() {
|
||||
Cell[] as = cells; Cell a;
|
||||
base = 0L;
|
||||
if (as != null) {
|
||||
for (int i = 0; i < as.length; ++i) {
|
||||
if ((a = as[i]) != null)
|
||||
a.value = 0L;
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
/**
|
||||
* Equivalent in effect to {@link #sum} followed by {@link
|
||||
* #reset}. This method may apply for example during quiescent
|
||||
* points between multithreaded computations. If there are
|
||||
* updates concurrent with this method, the returned value is
|
||||
* <em>not</em> guaranteed to be the final value occurring before
|
||||
* the reset.
|
||||
*
|
||||
* @return the sum
|
||||
*/
|
||||
public long sumThenReset() {
|
||||
Cell[] as = cells; Cell a;
|
||||
long sum = base;
|
||||
base = 0L;
|
||||
if (as != null) {
|
||||
for (int i = 0; i < as.length; ++i) {
|
||||
if ((a = as[i]) != null) {
|
||||
sum += a.value;
|
||||
a.value = 0L;
|
||||
}
|
||||
}
|
||||
}
|
||||
return sum;
|
||||
}
|
||||
|
||||
/**
|
||||
* Returns the String representation of the {@link #sum}.
|
||||
* @return the String representation of the {@link #sum}
|
||||
*/
|
||||
public String toString() {
|
||||
return Long.toString(sum());
|
||||
}
|
||||
|
||||
/**
|
||||
* Equivalent to {@link #sum}.
|
||||
*
|
||||
* @return the sum
|
||||
*/
|
||||
public long longValue() {
|
||||
return sum();
|
||||
}
|
||||
|
||||
/**
|
||||
* Returns the {@link #sum} as an {@code int} after a narrowing
|
||||
* primitive conversion.
|
||||
*/
|
||||
public int intValue() {
|
||||
return (int)sum();
|
||||
}
|
||||
|
||||
/**
|
||||
* Returns the {@link #sum} as a {@code float}
|
||||
* after a widening primitive conversion.
|
||||
*/
|
||||
public float floatValue() {
|
||||
return (float)sum();
|
||||
}
|
||||
|
||||
/**
|
||||
* Returns the {@link #sum} as a {@code double} after a widening
|
||||
* primitive conversion.
|
||||
*/
|
||||
public double doubleValue() {
|
||||
return (double)sum();
|
||||
}
|
||||
|
||||
/**
|
||||
* Serialization proxy, used to avoid reference to the non-public
|
||||
* Striped64 superclass in serialized forms.
|
||||
* @serial include
|
||||
*/
|
||||
private static class SerializationProxy implements Serializable {
|
||||
private static final long serialVersionUID = 7249069246863182397L;
|
||||
|
||||
/**
|
||||
* The current value returned by sum().
|
||||
* @serial
|
||||
*/
|
||||
private final long value;
|
||||
|
||||
SerializationProxy(LongAdder a) {
|
||||
value = a.sum();
|
||||
}
|
||||
|
||||
/**
|
||||
* Return a {@code LongAdder} object with initial state
|
||||
* held by this proxy.
|
||||
*
|
||||
* @return a {@code LongAdder} object with initial state
|
||||
* held by this proxy.
|
||||
*/
|
||||
private Object readResolve() {
|
||||
LongAdder a = new LongAdder();
|
||||
a.base = value;
|
||||
return a;
|
||||
}
|
||||
}
|
||||
|
||||
/**
|
||||
* Returns a
|
||||
* <a href="../../../../serialized-form.html#java.util.concurrent.atomic.LongAdder.SerializationProxy">
|
||||
* SerializationProxy</a>
|
||||
* representing the state of this instance.
|
||||
*
|
||||
* @return a {@link SerializationProxy}
|
||||
* representing the state of this instance
|
||||
*/
|
||||
private Object writeReplace() {
|
||||
return new SerializationProxy(this);
|
||||
}
|
||||
|
||||
/**
|
||||
* @param s the stream
|
||||
* @throws java.io.InvalidObjectException always
|
||||
*/
|
||||
private void readObject(java.io.ObjectInputStream s)
|
||||
throws java.io.InvalidObjectException {
|
||||
throw new java.io.InvalidObjectException("Proxy required");
|
||||
}
|
||||
|
||||
}
|
||||
|
|
@ -0,0 +1,395 @@
|
|||
package com.baeldung.falsesharing;
|
||||
|
||||
import sun.misc.Unsafe;
|
||||
|
||||
import java.lang.reflect.Field;
|
||||
import java.util.function.LongBinaryOperator;
|
||||
import java.util.function.DoubleBinaryOperator;
|
||||
import java.util.concurrent.ThreadLocalRandom;
|
||||
|
||||
/**
|
||||
* Copy-pasted from {@code java.util.concurrent.atomic.Striped64} class.
|
||||
*
|
||||
* A package-local class holding common representation and mechanics
|
||||
* for classes supporting dynamic striping on 64bit values. The class
|
||||
* extends Number so that concrete subclasses must publicly do so.
|
||||
*/
|
||||
@SuppressWarnings("serial")
|
||||
abstract class Striped64 extends Number {
|
||||
/*
|
||||
* This class maintains a lazily-initialized table of atomically
|
||||
* updated variables, plus an extra "base" field. The table size
|
||||
* is a power of two. Indexing uses masked per-thread hash codes.
|
||||
* Nearly all declarations in this class are package-private,
|
||||
* accessed directly by subclasses.
|
||||
*
|
||||
* Table entries are of class Cell; a variant of AtomicLong padded
|
||||
* (via @sun.misc.Contended) to reduce cache contention. Padding
|
||||
* is overkill for most Atomics because they are usually
|
||||
* irregularly scattered in memory and thus don't interfere much
|
||||
* with each other. But Atomic objects residing in arrays will
|
||||
* tend to be placed adjacent to each other, and so will most
|
||||
* often share cache lines (with a huge negative performance
|
||||
* impact) without this precaution.
|
||||
*
|
||||
* In part because Cells are relatively large, we avoid creating
|
||||
* them until they are needed. When there is no contention, all
|
||||
* updates are made to the base field. Upon first contention (a
|
||||
* failed CAS on base update), the table is initialized to size 2.
|
||||
* The table size is doubled upon further contention until
|
||||
* reaching the nearest power of two greater than or equal to the
|
||||
* number of CPUS. Table slots remain empty (null) until they are
|
||||
* needed.
|
||||
*
|
||||
* A single spinlock ("cellsBusy") is used for initializing and
|
||||
* resizing the table, as well as populating slots with new Cells.
|
||||
* There is no need for a blocking lock; when the lock is not
|
||||
* available, threads try other slots (or the base). During these
|
||||
* retries, there is increased contention and reduced locality,
|
||||
* which is still better than alternatives.
|
||||
*
|
||||
* The Thread probe fields maintained via ThreadLocalRandom serve
|
||||
* as per-thread hash codes. We let them remain uninitialized as
|
||||
* zero (if they come in this way) until they contend at slot
|
||||
* 0. They are then initialized to values that typically do not
|
||||
* often conflict with others. Contention and/or table collisions
|
||||
* are indicated by failed CASes when performing an update
|
||||
* operation. Upon a collision, if the table size is less than
|
||||
* the capacity, it is doubled in size unless some other thread
|
||||
* holds the lock. If a hashed slot is empty, and lock is
|
||||
* available, a new Cell is created. Otherwise, if the slot
|
||||
* exists, a CAS is tried. Retries proceed by "double hashing",
|
||||
* using a secondary hash (Marsaglia XorShift) to try to find a
|
||||
* free slot.
|
||||
*
|
||||
* The table size is capped because, when there are more threads
|
||||
* than CPUs, supposing that each thread were bound to a CPU,
|
||||
* there would exist a perfect hash function mapping threads to
|
||||
* slots that eliminates collisions. When we reach capacity, we
|
||||
* search for this mapping by randomly varying the hash codes of
|
||||
* colliding threads. Because search is random, and collisions
|
||||
* only become known via CAS failures, convergence can be slow,
|
||||
* and because threads are typically not bound to CPUS forever,
|
||||
* may not occur at all. However, despite these limitations,
|
||||
* observed contention rates are typically low in these cases.
|
||||
*
|
||||
* It is possible for a Cell to become unused when threads that
|
||||
* once hashed to it terminate, as well as in the case where
|
||||
* doubling the table causes no thread to hash to it under
|
||||
* expanded mask. We do not try to detect or remove such cells,
|
||||
* under the assumption that for long-running instances, observed
|
||||
* contention levels will recur, so the cells will eventually be
|
||||
* needed again; and for short-lived ones, it does not matter.
|
||||
*/
|
||||
|
||||
/**
|
||||
* Padded variant of AtomicLong supporting only raw accesses plus CAS.
|
||||
*
|
||||
* JVM intrinsics note: It would be possible to use a release-only
|
||||
* form of CAS here, if it were provided.
|
||||
*/
|
||||
@sun.misc.Contended static final class Cell {
|
||||
volatile long value;
|
||||
Cell(long x) { value = x; }
|
||||
final boolean cas(long cmp, long val) {
|
||||
return UNSAFE.compareAndSwapLong(this, valueOffset, cmp, val);
|
||||
}
|
||||
|
||||
// Unsafe mechanics
|
||||
private static final sun.misc.Unsafe UNSAFE;
|
||||
private static final long valueOffset;
|
||||
static {
|
||||
try {
|
||||
UNSAFE = getUnsafe();
|
||||
Class<?> ak = Striped64.Cell.class;
|
||||
valueOffset = UNSAFE.objectFieldOffset
|
||||
(ak.getDeclaredField("value"));
|
||||
} catch (Exception e) {
|
||||
throw new Error(e);
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
/** Number of CPUS, to place bound on table size */
|
||||
static final int NCPU = Runtime.getRuntime().availableProcessors();
|
||||
|
||||
/**
|
||||
* Table of cells. When non-null, size is a power of 2.
|
||||
*/
|
||||
transient volatile Striped64.Cell[] cells;
|
||||
|
||||
/**
|
||||
* Base value, used mainly when there is no contention, but also as
|
||||
* a fallback during table initialization races. Updated via CAS.
|
||||
*/
|
||||
transient volatile long base;
|
||||
|
||||
/**
|
||||
* Spinlock (locked via CAS) used when resizing and/or creating Cells.
|
||||
*/
|
||||
transient volatile int cellsBusy;
|
||||
|
||||
/**
|
||||
* Package-private default constructor
|
||||
*/
|
||||
Striped64() {
|
||||
}
|
||||
|
||||
/**
|
||||
* CASes the base field.
|
||||
*/
|
||||
final boolean casBase(long cmp, long val) {
|
||||
return UNSAFE.compareAndSwapLong(this, BASE, cmp, val);
|
||||
}
|
||||
|
||||
/**
|
||||
* CASes the cellsBusy field from 0 to 1 to acquire lock.
|
||||
*/
|
||||
final boolean casCellsBusy() {
|
||||
return UNSAFE.compareAndSwapInt(this, CELLSBUSY, 0, 1);
|
||||
}
|
||||
|
||||
/**
|
||||
* Returns the probe value for the current thread.
|
||||
* Duplicated from ThreadLocalRandom because of packaging restrictions.
|
||||
*/
|
||||
static final int getProbe() {
|
||||
return UNSAFE.getInt(Thread.currentThread(), PROBE);
|
||||
}
|
||||
|
||||
/**
|
||||
* Pseudo-randomly advances and records the given probe value for the
|
||||
* given thread.
|
||||
* Duplicated from ThreadLocalRandom because of packaging restrictions.
|
||||
*/
|
||||
static final int advanceProbe(int probe) {
|
||||
probe ^= probe << 13; // xorshift
|
||||
probe ^= probe >>> 17;
|
||||
probe ^= probe << 5;
|
||||
UNSAFE.putInt(Thread.currentThread(), PROBE, probe);
|
||||
return probe;
|
||||
}
|
||||
|
||||
/**
|
||||
* Handles cases of updates involving initialization, resizing,
|
||||
* creating new Cells, and/or contention. See above for
|
||||
* explanation. This method suffers the usual non-modularity
|
||||
* problems of optimistic retry code, relying on rechecked sets of
|
||||
* reads.
|
||||
*
|
||||
* @param x the value
|
||||
* @param fn the update function, or null for add (this convention
|
||||
* avoids the need for an extra field or function in LongAdder).
|
||||
* @param wasUncontended false if CAS failed before call
|
||||
*/
|
||||
final void longAccumulate(long x, LongBinaryOperator fn,
|
||||
boolean wasUncontended) {
|
||||
int h;
|
||||
if ((h = getProbe()) == 0) {
|
||||
ThreadLocalRandom.current(); // force initialization
|
||||
h = getProbe();
|
||||
wasUncontended = true;
|
||||
}
|
||||
boolean collide = false; // True if last slot nonempty
|
||||
for (;;) {
|
||||
Striped64.Cell[] as; Striped64.Cell a; int n; long v;
|
||||
if ((as = cells) != null && (n = as.length) > 0) {
|
||||
if ((a = as[(n - 1) & h]) == null) {
|
||||
if (cellsBusy == 0) { // Try to attach new Cell
|
||||
Striped64.Cell r = new Striped64.Cell(x); // Optimistically create
|
||||
if (cellsBusy == 0 && casCellsBusy()) {
|
||||
boolean created = false;
|
||||
try { // Recheck under lock
|
||||
Striped64.Cell[] rs; int m, j;
|
||||
if ((rs = cells) != null &&
|
||||
(m = rs.length) > 0 &&
|
||||
rs[j = (m - 1) & h] == null) {
|
||||
rs[j] = r;
|
||||
created = true;
|
||||
}
|
||||
} finally {
|
||||
cellsBusy = 0;
|
||||
}
|
||||
if (created)
|
||||
break;
|
||||
continue; // Slot is now non-empty
|
||||
}
|
||||
}
|
||||
collide = false;
|
||||
}
|
||||
else if (!wasUncontended) // CAS already known to fail
|
||||
wasUncontended = true; // Continue after rehash
|
||||
else if (a.cas(v = a.value, ((fn == null) ? v + x :
|
||||
fn.applyAsLong(v, x))))
|
||||
break;
|
||||
else if (n >= NCPU || cells != as)
|
||||
collide = false; // At max size or stale
|
||||
else if (!collide)
|
||||
collide = true;
|
||||
else if (cellsBusy == 0 && casCellsBusy()) {
|
||||
try {
|
||||
if (cells == as) { // Expand table unless stale
|
||||
Striped64.Cell[] rs = new Striped64.Cell[n << 1];
|
||||
for (int i = 0; i < n; ++i)
|
||||
rs[i] = as[i];
|
||||
cells = rs;
|
||||
}
|
||||
} finally {
|
||||
cellsBusy = 0;
|
||||
}
|
||||
collide = false;
|
||||
continue; // Retry with expanded table
|
||||
}
|
||||
h = advanceProbe(h);
|
||||
}
|
||||
else if (cellsBusy == 0 && cells == as && casCellsBusy()) {
|
||||
boolean init = false;
|
||||
try { // Initialize table
|
||||
if (cells == as) {
|
||||
Striped64.Cell[] rs = new Striped64.Cell[2];
|
||||
rs[h & 1] = new Striped64.Cell(x);
|
||||
cells = rs;
|
||||
init = true;
|
||||
}
|
||||
} finally {
|
||||
cellsBusy = 0;
|
||||
}
|
||||
if (init)
|
||||
break;
|
||||
}
|
||||
else if (casBase(v = base, ((fn == null) ? v + x :
|
||||
fn.applyAsLong(v, x))))
|
||||
break; // Fall back on using base
|
||||
}
|
||||
}
|
||||
|
||||
/**
|
||||
* Same as longAccumulate, but injecting long/double conversions
|
||||
* in too many places to sensibly merge with long version, given
|
||||
* the low-overhead requirements of this class. So must instead be
|
||||
* maintained by copy/paste/adapt.
|
||||
*/
|
||||
final void doubleAccumulate(double x, DoubleBinaryOperator fn,
|
||||
boolean wasUncontended) {
|
||||
int h;
|
||||
if ((h = getProbe()) == 0) {
|
||||
ThreadLocalRandom.current(); // force initialization
|
||||
h = getProbe();
|
||||
wasUncontended = true;
|
||||
}
|
||||
boolean collide = false; // True if last slot nonempty
|
||||
for (;;) {
|
||||
Striped64.Cell[] as; Striped64.Cell a; int n; long v;
|
||||
if ((as = cells) != null && (n = as.length) > 0) {
|
||||
if ((a = as[(n - 1) & h]) == null) {
|
||||
if (cellsBusy == 0) { // Try to attach new Cell
|
||||
Striped64.Cell r = new Striped64.Cell(Double.doubleToRawLongBits(x));
|
||||
if (cellsBusy == 0 && casCellsBusy()) {
|
||||
boolean created = false;
|
||||
try { // Recheck under lock
|
||||
Striped64.Cell[] rs; int m, j;
|
||||
if ((rs = cells) != null &&
|
||||
(m = rs.length) > 0 &&
|
||||
rs[j = (m - 1) & h] == null) {
|
||||
rs[j] = r;
|
||||
created = true;
|
||||
}
|
||||
} finally {
|
||||
cellsBusy = 0;
|
||||
}
|
||||
if (created)
|
||||
break;
|
||||
continue; // Slot is now non-empty
|
||||
}
|
||||
}
|
||||
collide = false;
|
||||
}
|
||||
else if (!wasUncontended) // CAS already known to fail
|
||||
wasUncontended = true; // Continue after rehash
|
||||
else if (a.cas(v = a.value,
|
||||
((fn == null) ?
|
||||
Double.doubleToRawLongBits
|
||||
(Double.longBitsToDouble(v) + x) :
|
||||
Double.doubleToRawLongBits
|
||||
(fn.applyAsDouble
|
||||
(Double.longBitsToDouble(v), x)))))
|
||||
break;
|
||||
else if (n >= NCPU || cells != as)
|
||||
collide = false; // At max size or stale
|
||||
else if (!collide)
|
||||
collide = true;
|
||||
else if (cellsBusy == 0 && casCellsBusy()) {
|
||||
try {
|
||||
if (cells == as) { // Expand table unless stale
|
||||
Striped64.Cell[] rs = new Striped64.Cell[n << 1];
|
||||
for (int i = 0; i < n; ++i)
|
||||
rs[i] = as[i];
|
||||
cells = rs;
|
||||
}
|
||||
} finally {
|
||||
cellsBusy = 0;
|
||||
}
|
||||
collide = false;
|
||||
continue; // Retry with expanded table
|
||||
}
|
||||
h = advanceProbe(h);
|
||||
}
|
||||
else if (cellsBusy == 0 && cells == as && casCellsBusy()) {
|
||||
boolean init = false;
|
||||
try { // Initialize table
|
||||
if (cells == as) {
|
||||
Striped64.Cell[] rs = new Striped64.Cell[2];
|
||||
rs[h & 1] = new Striped64.Cell(Double.doubleToRawLongBits(x));
|
||||
cells = rs;
|
||||
init = true;
|
||||
}
|
||||
} finally {
|
||||
cellsBusy = 0;
|
||||
}
|
||||
if (init)
|
||||
break;
|
||||
}
|
||||
else if (casBase(v = base,
|
||||
((fn == null) ?
|
||||
Double.doubleToRawLongBits
|
||||
(Double.longBitsToDouble(v) + x) :
|
||||
Double.doubleToRawLongBits
|
||||
(fn.applyAsDouble
|
||||
(Double.longBitsToDouble(v), x)))))
|
||||
break; // Fall back on using base
|
||||
}
|
||||
}
|
||||
|
||||
// Unsafe mechanics
|
||||
private static final sun.misc.Unsafe UNSAFE;
|
||||
private static final long BASE;
|
||||
private static final long CELLSBUSY;
|
||||
private static final long PROBE;
|
||||
static {
|
||||
try {
|
||||
UNSAFE = getUnsafe();
|
||||
Class<?> sk = Striped64.class;
|
||||
BASE = UNSAFE.objectFieldOffset
|
||||
(sk.getDeclaredField("base"));
|
||||
CELLSBUSY = UNSAFE.objectFieldOffset
|
||||
(sk.getDeclaredField("cellsBusy"));
|
||||
Class<?> tk = Thread.class;
|
||||
PROBE = UNSAFE.objectFieldOffset
|
||||
(tk.getDeclaredField("threadLocalRandomProbe"));
|
||||
} catch (Exception e) {
|
||||
throw new Error(e);
|
||||
}
|
||||
}
|
||||
|
||||
private static Unsafe getUnsafe() {
|
||||
try {
|
||||
Field field = Unsafe.class.getDeclaredField("theUnsafe");
|
||||
field.setAccessible(true);
|
||||
|
||||
return (Unsafe) field.get(null);
|
||||
} catch (Exception e) {
|
||||
throw new RuntimeException(e);
|
||||
}
|
||||
}
|
||||
|
||||
}
|
||||
Loading…
Reference in New Issue