| 86 |
|
static final int NCPU = Runtime.getRuntime().availableProcessors(); |
| 87 |
|
|
| 88 |
|
/** |
| 89 |
+ |
* The table size set upon first use when default-constructed |
| 90 |
+ |
*/ |
| 91 |
+ |
private static final int DEFAULT_ARRAY_SIZE = 8; |
| 92 |
+ |
|
| 93 |
+ |
/** |
| 94 |
|
* Padded version of AtomicLong |
| 95 |
|
*/ |
| 96 |
|
static final class Adder extends AtomicLong { |
| 127 |
|
static final ThreadHashCode threadHashCode = new ThreadHashCode(); |
| 128 |
|
|
| 129 |
|
/** |
| 130 |
< |
* Table of adders. Minimum size 2. Size grows to be at most NCPU. |
| 130 |
> |
* Table of adders. Size is power of two, grows to be at most NCPU. |
| 131 |
|
*/ |
| 132 |
|
private transient volatile Adder[] adders; |
| 133 |
|
|
| 134 |
|
/** |
| 135 |
|
* Serves as a lock when resizing and/or creating Adders. There |
| 136 |
< |
* is no need for a blocking lock: When busy, other threads try |
| 137 |
< |
* other slots. |
| 136 |
> |
* is no need for a blocking lock: Except during initialization |
| 137 |
> |
* races, when busy, other threads try other slots. |
| 138 |
|
*/ |
| 139 |
|
private final AtomicInteger mutex; |
| 140 |
|
|
| 154 |
|
* will concurrently update the sum. |
| 155 |
|
*/ |
| 156 |
|
public StripedAdder(int expectedContention) { |
| 157 |
< |
int cap = (expectedContention < NCPU) ? expectedContention : NCPU; |
| 158 |
< |
int size = 2; |
| 159 |
< |
while (size < cap) |
| 160 |
< |
size <<= 1; |
| 157 |
> |
int size; |
| 158 |
> |
if (expectedContention > 0) { |
| 159 |
> |
int cap = (expectedContention < NCPU) ? expectedContention : NCPU; |
| 160 |
> |
size = 1; |
| 161 |
> |
while (size < cap) |
| 162 |
> |
size <<= 1; |
| 163 |
> |
} |
| 164 |
> |
else |
| 165 |
> |
size = 0; |
| 166 |
|
Adder[] as = new Adder[size]; |
| 167 |
|
for (int i = 0; i < size; ++i) |
| 168 |
|
as[i] = new Adder(0); |
| 191 |
|
private void retryAdd(long x, HashCode hc) { |
| 192 |
|
int h = hc.code; |
| 193 |
|
final AtomicInteger mutex = this.mutex; |
| 194 |
< |
AtomicInteger lock = null; // nonnull when held |
| 195 |
< |
try { |
| 196 |
< |
for (;;) { |
| 197 |
< |
Adder[] as; Adder a; long v; int n, k; // locals for volatiles |
| 198 |
< |
boolean needLock = true; |
| 199 |
< |
if ((as = adders) == null || (n = as.length) < 1) { |
| 200 |
< |
if (lock != null) // default-initialize |
| 201 |
< |
adders = new Adder[2]; |
| 202 |
< |
} |
| 193 |
< |
else if ((a = as[k = h & (n - 1)]) == null) { |
| 194 |
< |
if (lock != null) { // attach new adder |
| 195 |
< |
as[k] = new Adder(x); |
| 196 |
< |
break; |
| 194 |
> |
for (boolean retried = false; ; retried = true) { |
| 195 |
> |
Adder[] as; Adder a; long v; int n, k; // Locals for volatiles |
| 196 |
> |
if ((as = adders) == null || (n = as.length) < 1) { |
| 197 |
> |
if (mutex.get() == 0 && mutex.compareAndSet(0, 1)) { |
| 198 |
> |
try { |
| 199 |
> |
if (adders == null) // Default-initialize |
| 200 |
> |
adders = new Adder[DEFAULT_ARRAY_SIZE]; |
| 201 |
> |
} finally { |
| 202 |
> |
mutex.set(0); |
| 203 |
|
} |
| 204 |
|
} |
| 205 |
< |
else if (a.compareAndSet(v = a.get(), v + x)) |
| 206 |
< |
break; |
| 207 |
< |
else if (n >= NCPU) // cannot expand |
| 208 |
< |
needLock = false; |
| 209 |
< |
else if (lock != null) // expand table |
| 210 |
< |
adders = Arrays.copyOf(as, n << 1); |
| 211 |
< |
|
| 212 |
< |
if (lock == null) { |
| 213 |
< |
if (needLock && mutex.get() == 0 && |
| 214 |
< |
mutex.compareAndSet(0, 1)) |
| 215 |
< |
lock = mutex; |
| 216 |
< |
else { // try elsewhere |
| 217 |
< |
h ^= h << 13; // Marsaglia XorShift |
| 218 |
< |
h ^= h >>> 17; |
| 219 |
< |
h ^= h << 5; |
| 205 |
> |
else |
| 206 |
> |
Thread.yield(); // initialization race |
| 207 |
> |
} |
| 208 |
> |
else if ((a = as[k = h & (n - 1)]) != null && |
| 209 |
> |
retried && a.compareAndSet(v = a.get(), v + x)) |
| 210 |
> |
break; |
| 211 |
> |
else if ((a == null || n < NCPU) && |
| 212 |
> |
mutex.get() == 0 && mutex.compareAndSet(0, 1)) { |
| 213 |
> |
boolean created = false; |
| 214 |
> |
try { |
| 215 |
> |
if (adders == as) { |
| 216 |
> |
if (as[k] == null) { |
| 217 |
> |
as[k] = new Adder(x); |
| 218 |
> |
created = true; |
| 219 |
> |
} |
| 220 |
> |
else { // Expand table |
| 221 |
> |
Adder[] rs = new Adder[n << 1]; |
| 222 |
> |
for (int i = 0; i < n; ++i) |
| 223 |
> |
rs[i] = as[i]; |
| 224 |
> |
adders = rs; |
| 225 |
> |
} |
| 226 |
|
} |
| 227 |
+ |
} finally { |
| 228 |
+ |
mutex.set(0); |
| 229 |
|
} |
| 230 |
+ |
if (created) |
| 231 |
+ |
break; |
| 232 |
+ |
} |
| 233 |
+ |
else { // Try elsewhere |
| 234 |
+ |
h ^= h << 13; |
| 235 |
+ |
h ^= h >>> 17; // Marsaglia XorShift |
| 236 |
+ |
h ^= h << 5; |
| 237 |
|
} |
| 217 |
– |
} finally { |
| 218 |
– |
if (lock != null) |
| 219 |
– |
lock.set(0); |
| 238 |
|
} |
| 239 |
< |
if (hc.code != h) // avoid unneeded writes |
| 222 |
< |
hc.code = h; |
| 239 |
> |
hc.code = h; |
| 240 |
|
} |
| 241 |
|
|
| 242 |
|
/** |
