| 14 |
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import java.io.ObjectOutputStream; |
| 15 |
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|
| 16 |
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/** |
| 17 |
< |
* A set of variables that together maintain a sum. When updates |
| 18 |
< |
* (method {@link #add}) are contended across threads, this set of |
| 19 |
< |
* adder variables may grow dynamically to reduce contention. Method |
| 20 |
< |
* {@link #sum} returns the current combined total across these |
| 21 |
< |
* adders. This value is <em>NOT</em> an atomic snapshot (concurrent |
| 22 |
< |
* updates may occur while the sum is being calculated), and so cannot |
| 23 |
< |
* be used alone for fine-grained synchronization control. |
| 17 |
> |
* One or more variables that together maintain an initially zero sum. |
| 18 |
> |
* When updates (method {@link #add}) are contended across threads, |
| 19 |
> |
* the set of variables may grow dynamically to reduce contention. |
| 20 |
|
* |
| 21 |
< |
* <p> This class may be applicable when many threads frequently |
| 22 |
< |
* update a common sum that is used for purposes such as collecting |
| 23 |
< |
* statistics. In this case, performance may be significantly faster |
| 24 |
< |
* than using a shared {@link AtomicLong}, at the expense of using |
| 25 |
< |
* more space. On the other hand, if it is known that only one thread |
| 26 |
< |
* can ever update the sum, performance may be significantly slower |
| 21 |
> |
* <p> This class is usually preferable to {@link AtomicLong} when |
| 22 |
> |
* multiple threads update a common sum that is used for purposes such |
| 23 |
> |
* as collecting statistics, not for fine-grained synchronization |
| 24 |
> |
* control. Under high update contention, throughput of this class is |
| 25 |
> |
* expected to be significantly higher, at the expense of higher space |
| 26 |
> |
* consumption. Under low contention, this class imposes very little |
| 27 |
> |
* time and space overhead compared to AtomicLong. On the other hand, |
| 28 |
> |
* in contexts where it is statically known that only one thread can |
| 29 |
> |
* ever update a sum, time and space overhead is noticeably greater |
| 30 |
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* than just updating a local variable. |
| 31 |
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* |
| 32 |
< |
* <p>A StripedAdder may optionally be constructed with a given |
| 33 |
< |
* expected contention level; i.e., the number of threads that are |
| 34 |
< |
* expected to concurrently update the sum. Supplying an accurate |
| 35 |
< |
* value may improve performance by reducing the need for dynamic |
| 36 |
< |
* adjustment. |
| 32 |
> |
* <p> Method {@link #sum} returns the current combined total across |
| 33 |
> |
* the variables maintaining the sum. This value is <em>NOT</em> an |
| 34 |
> |
* atomic snapshot: Concurrent updates may occur while the sum is |
| 35 |
> |
* being calculated. However, updates cannot be "lost", so invocation |
| 36 |
> |
* of <code>sum</code> in the absence of concurrent updates always |
| 37 |
> |
* returns an accurate result. The sum may also be <code>reset</code> |
| 38 |
> |
* to zero, as an alternative to creating a new adder. However, |
| 39 |
> |
* method {@link #reset} is intrinsically racy, so should only be used |
| 40 |
> |
* when it is known that no threads are concurrently updating the sum. |
| 41 |
> |
* |
| 42 |
> |
* <p><em>jsr166e note: This class is targeted to be placed in |
| 43 |
> |
* java.util.concurrent.atomic<em> |
| 44 |
|
* |
| 45 |
|
* @author Doug Lea |
| 46 |
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*/ |
| 48 |
|
private static final long serialVersionUID = 7249069246863182397L; |
| 49 |
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|
| 50 |
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/* |
| 51 |
< |
* A StripedAdder maintains a table of Atomic long variables. The |
| 52 |
< |
* table is indexed by per-thread hash codes. |
| 51 |
> |
* A StripedAdder maintains a lazily-initialized table of |
| 52 |
> |
* atomically updated variables, plus an extra "base" field. The |
| 53 |
> |
* table size is a power of two. Indexing uses masked per-thread |
| 54 |
> |
* hash codes |
| 55 |
> |
* |
| 56 |
> |
* Table entries are of class Cell; a variant of AtomicLong padded |
| 57 |
> |
* to reduce cache contention on most processors. Padding is |
| 58 |
> |
* overkill for most Atomics because they are usually irregularly |
| 59 |
> |
* scattered in memory and thus don't interfere much with each |
| 60 |
> |
* other. But Atomic objects residing in arrays will tend to be |
| 61 |
> |
* placed adjacent to each other, and so will most often share |
| 62 |
> |
* cache lines (with a huge negative performance impact) without |
| 63 |
> |
* this precaution. |
| 64 |
|
* |
| 65 |
< |
* Table entries are of class Adder; a variant of AtomicLong |
| 66 |
< |
* padded to reduce cache contention on most processors. Padding |
| 67 |
< |
* is overkill for most Atomics because they are usually |
| 68 |
< |
* irregularly scattered in memory and thus don't interfere much |
| 69 |
< |
* with each other. But Atomic objects residing in arrays will |
| 70 |
< |
* tend to be placed adjacent to each other, and so will most |
| 71 |
< |
* often share cache lines (with a huge negative performance |
| 55 |
< |
* impact) without this precaution. |
| 56 |
< |
* |
| 57 |
< |
* Because Adders are relatively large, we avoid creating them |
| 58 |
< |
* until they are needed. On the other hand, we try to create them |
| 59 |
< |
* on any sign of contention. |
| 65 |
> |
* In part because Cells are relatively large, we avoid creating |
| 66 |
> |
* them until they are needed. When there is no contention, all |
| 67 |
> |
* updates are made to the base field. Upon first contention (a |
| 68 |
> |
* failed CAS on base update), the table is initialized to size 2. |
| 69 |
> |
* The table size is doubled upon further contention until |
| 70 |
> |
* reaching the nearest power of two greater than or equal to the |
| 71 |
> |
* number of CPUS. |
| 72 |
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* |
| 73 |
|
* Per-thread hash codes are initialized to random values. |
| 74 |
< |
* Collisions are indicated by failed CASes when performing an add |
| 75 |
< |
* operation (see method retryAdd). Upon a collision, if the table |
| 76 |
< |
* size is less than the capacity, it is doubled in size unless |
| 77 |
< |
* some other thread holds lock. If a hashed slot is empty, and |
| 78 |
< |
* lock is available, a new Adder is created. Otherwise, if the |
| 79 |
< |
* slot exists, a CAS is tried. Retries proceed by "double |
| 80 |
< |
* hashing", using a secondary hash (Marsaglia XorShift) to try to |
| 81 |
< |
* find a free slot. |
| 82 |
< |
* |
| 83 |
< |
* By default, the table is lazily initialized. Upon first use, |
| 84 |
< |
* the table is set to size 1, and contains a single Adder. The |
| 85 |
< |
* maximum table size is bounded by nearest power of two >= the |
| 86 |
< |
* number of CPUS. The table size is capped because, when there |
| 87 |
< |
* are more threads than CPUs, supposing that each thread were |
| 88 |
< |
* bound to a CPU, there would exist a perfect hash function |
| 89 |
< |
* mapping threads to slots that eliminates collisions. When we |
| 90 |
< |
* reach capacity, we search for this mapping by randomly varying |
| 91 |
< |
* the hash codes of colliding threads. Because search is random, |
| 92 |
< |
* and failures only become known via CAS failures, convergence |
| 93 |
< |
* will be slow, and because threads are typically not bound to |
| 94 |
< |
* CPUS forever, may not occur at all. However, despite these |
| 95 |
< |
* limitations, observed contention is typically low in these |
| 96 |
< |
* cases. |
| 97 |
< |
* |
| 98 |
< |
* A single spinlock is used for resizing the table as well as |
| 99 |
< |
* populating slots with new Adders. After initialization, there |
| 100 |
< |
* is no need for a blocking lock: Upon lock contention, threads |
| 101 |
< |
* try other slots rather than blocking. After initialization, at |
| 102 |
< |
* least one slot exists, so retries will eventually find a |
| 103 |
< |
* candidate Adder. During these retries, there is increased |
| 104 |
< |
* contention and reduced locality, which is still better than |
| 105 |
< |
* alternatives. |
| 74 |
> |
* Contention and/or table collisions are indicated by failed |
| 75 |
> |
* CASes when performing an add operation (see method |
| 76 |
> |
* retryAdd). Upon a collision, if the table size is less than the |
| 77 |
> |
* capacity, it is doubled in size unless some other thread holds |
| 78 |
> |
* the lock. If a hashed slot is empty, and lock is available, a |
| 79 |
> |
* new Cell is created. Otherwise, if the slot exists, a CAS is |
| 80 |
> |
* tried. Retries proceed by "double hashing", using a secondary |
| 81 |
> |
* hash (Marsaglia XorShift) to try to find a free slot. |
| 82 |
> |
* |
| 83 |
> |
* The table size is capped because, when there are more threads |
| 84 |
> |
* than CPUs, supposing that each thread were bound to a CPU, |
| 85 |
> |
* there would exist a perfect hash function mapping threads to |
| 86 |
> |
* slots that eliminates collisions. When we reach capacity, we |
| 87 |
> |
* search for this mapping by randomly varying the hash codes of |
| 88 |
> |
* colliding threads. Because search is random, and collisions |
| 89 |
> |
* only become known via CAS failures, convergence can be slow, |
| 90 |
> |
* and because threads are typically not bound to CPUS forever, |
| 91 |
> |
* may not occur at all. However, despite these limitations, |
| 92 |
> |
* observed contention rates are typically low in these cases. |
| 93 |
> |
* |
| 94 |
> |
* A single spinlock is used for initializing and resizing the |
| 95 |
> |
* table, as well as populating slots with new Cells. There is no |
| 96 |
> |
* need for a blocking lock: Upon lock contention, threads try |
| 97 |
> |
* other slots (or the base) rather than blocking. During these |
| 98 |
> |
* retries, there is increased contention and reduced locality, |
| 99 |
> |
* which is still better than alternatives. |
| 100 |
> |
* |
| 101 |
> |
* It is possible for a Cell to become unused when threads that |
| 102 |
> |
* once hashed to it terminate, as well as in the case where |
| 103 |
> |
* doubling the table causes no thread to hash to it under |
| 104 |
> |
* expanded mask. We do not try to detect or remove such cells, |
| 105 |
> |
* under the assumption that for long-running adders, observed |
| 106 |
> |
* contention levels will recur, so the cells will eventually be |
| 107 |
> |
* needed again; and for short-lived ones, it does not matter. |
| 108 |
> |
* |
| 109 |
|
*/ |
| 110 |
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|
| 111 |
|
private static final int NCPU = Runtime.getRuntime().availableProcessors(); |
| 115 |
|
* between pads, hoping that the JVM doesn't reorder them. |
| 116 |
|
* Updates are via inlined CAS in methods add and retryAdd. |
| 117 |
|
*/ |
| 118 |
< |
static final class Adder { |
| 118 |
> |
static final class Cell { |
| 119 |
|
volatile long p0, p1, p2, p3, p4, p5, p6; |
| 120 |
|
volatile long value; |
| 121 |
|
volatile long q0, q1, q2, q3, q4, q5, q6; |
| 122 |
< |
Adder(long x) { value = x; } |
| 122 |
> |
Cell(long x) { value = x; } |
| 123 |
|
} |
| 124 |
|
|
| 125 |
|
/** |
| 130 |
|
static final Random rng = new Random(); |
| 131 |
|
int code; |
| 132 |
|
HashCode() { |
| 133 |
< |
int h = rng.nextInt(); // Avoid zero, because of xorShift rehash |
| 133 |
> |
int h = rng.nextInt(); // Avoid zero to allow xorShift rehash |
| 134 |
|
code = (h == 0) ? 1 : h; |
| 135 |
|
} |
| 136 |
|
} |
| 151 |
|
static final ThreadHashCode threadHashCode = new ThreadHashCode(); |
| 152 |
|
|
| 153 |
|
/** |
| 154 |
< |
* Table of adders. When non-null, size is a power of 2. |
| 154 |
> |
* Table of cells. When non-null, size is a power of 2. |
| 155 |
|
*/ |
| 156 |
< |
private transient volatile Adder[] adders; |
| 156 |
> |
private transient volatile Cell[] cells; |
| 157 |
|
|
| 158 |
|
/** |
| 159 |
< |
* Spinlock (locked via CAS) used when resizing and/or creating Adders. |
| 159 |
> |
* Base sum, used mainly when there is no contention, but also as |
| 160 |
> |
* a fallback during table initializion races. Updated via CAS. |
| 161 |
|
*/ |
| 162 |
< |
private volatile int busy; |
| 162 |
> |
private transient volatile long base; |
| 163 |
|
|
| 164 |
|
/** |
| 165 |
< |
* Creates a new adder with zero sum. |
| 165 |
> |
* Spinlock (locked via CAS) used when resizing and/or creating Cells. |
| 166 |
|
*/ |
| 167 |
< |
public StripedAdder() { |
| 152 |
< |
} |
| 167 |
> |
private transient volatile int busy; |
| 168 |
|
|
| 169 |
|
/** |
| 170 |
< |
* Creates a new adder with zero sum, and with stripes presized |
| 156 |
< |
* for the given expected contention level. |
| 157 |
< |
* |
| 158 |
< |
* @param expectedContention the expected number of threads that |
| 159 |
< |
* will concurrently update the sum. |
| 170 |
> |
* Creates a new adder with initial sum of zero. |
| 171 |
|
*/ |
| 172 |
< |
public StripedAdder(int expectedContention) { |
| 162 |
< |
int cap = (expectedContention < NCPU) ? expectedContention : NCPU; |
| 163 |
< |
int size = 1; |
| 164 |
< |
while (size < cap) |
| 165 |
< |
size <<= 1; |
| 166 |
< |
Adder[] as = new Adder[size]; |
| 167 |
< |
for (int i = 0; i < size; ++i) |
| 168 |
< |
as[i] = new Adder(0); |
| 169 |
< |
this.adders = as; |
| 172 |
> |
public StripedAdder() { |
| 173 |
|
} |
| 174 |
|
|
| 175 |
|
/** |
| 178 |
|
* @param x the value to add |
| 179 |
|
*/ |
| 180 |
|
public void add(long x) { |
| 181 |
< |
Adder[] as; Adder a; int n; // locals to hold volatile reads |
| 182 |
< |
HashCode hc = threadHashCode.get(); |
| 183 |
< |
int h = hc.code; |
| 184 |
< |
boolean contended; |
| 185 |
< |
if ((as = adders) != null && (n = as.length) > 0 && |
| 186 |
< |
(a = as[(n - 1) & h]) != null) { |
| 187 |
< |
long v = a.value; |
| 188 |
< |
if (UNSAFE.compareAndSwapLong(a, valueOffset, v, v + x)) |
| 189 |
< |
return; |
| 190 |
< |
contended = true; |
| 181 |
> |
Cell[] as; long v; HashCode hc; Cell a; int n; boolean contended; |
| 182 |
> |
if ((as = cells) != null || |
| 183 |
> |
!UNSAFE.compareAndSwapLong(this, baseOffset, v = base, v + x)) { |
| 184 |
> |
int h = (hc = threadHashCode.get()).code; |
| 185 |
> |
if (as != null && (n = as.length) > 0 && |
| 186 |
> |
(a = as[(n - 1) & h]) != null) { |
| 187 |
> |
if (UNSAFE.compareAndSwapLong(a, valueOffset, |
| 188 |
> |
v = a.value, v + x)) |
| 189 |
> |
return; |
| 190 |
> |
contended = true; |
| 191 |
> |
} |
| 192 |
> |
else |
| 193 |
> |
contended = false; |
| 194 |
> |
retryAdd(x, hc, contended); |
| 195 |
|
} |
| 189 |
– |
else |
| 190 |
– |
contended = false; |
| 191 |
– |
retryAdd(x, hc, contended); |
| 196 |
|
} |
| 197 |
|
|
| 198 |
|
/** |
| 199 |
|
* Handle cases of add involving initialization, resizing, |
| 200 |
< |
* creating new Adders, and/or contention. See above for |
| 200 |
> |
* creating new Cells, and/or contention. See above for |
| 201 |
|
* explanation. This method suffers the usual non-modularity |
| 202 |
|
* problems of optimistic retry code, relying on rechecked sets of |
| 203 |
|
* reads. |
| 210 |
|
int h = hc.code; |
| 211 |
|
boolean collide = false; // true if last slot nonempty |
| 212 |
|
for (;;) { |
| 213 |
< |
Adder[] as; Adder a; int n; |
| 214 |
< |
if ((as = adders) != null && (n = as.length) > 0) { |
| 213 |
> |
Cell[] as; Cell a; int n; |
| 214 |
> |
if ((as = cells) != null && (n = as.length) > 0) { |
| 215 |
|
if ((a = as[(n - 1) & h]) == null) { |
| 216 |
< |
if (busy == 0) { // Try to attach new Adder |
| 217 |
< |
Adder r = new Adder(x); // Optimistically create |
| 216 |
> |
if (busy == 0) { // Try to attach new Cell |
| 217 |
> |
Cell r = new Cell(x); // Optimistically create |
| 218 |
|
if (busy == 0 && |
| 219 |
|
UNSAFE.compareAndSwapInt(this, busyOffset, 0, 1)) { |
| 220 |
|
boolean created = false; |
| 221 |
|
try { // Recheck under lock |
| 222 |
< |
Adder[] rs; int m, j; |
| 223 |
< |
if ((rs = adders) != null && |
| 222 |
> |
Cell[] rs; int m, j; |
| 223 |
> |
if ((rs = cells) != null && |
| 224 |
|
(m = rs.length) > 0 && |
| 225 |
|
rs[j = (m - 1) & h] == null) { |
| 226 |
|
rs[j] = r; |
| 244 |
|
break; |
| 245 |
|
if (!collide) |
| 246 |
|
collide = true; |
| 247 |
< |
else if (n >= NCPU || adders != as) |
| 247 |
> |
else if (n >= NCPU || cells != as) |
| 248 |
|
collide = false; // Can't expand |
| 249 |
|
else if (busy == 0 && |
| 250 |
|
UNSAFE.compareAndSwapInt(this, busyOffset, 0, 1)) { |
| 251 |
|
collide = false; |
| 252 |
|
try { |
| 253 |
< |
if (adders == as) { // Expand table |
| 254 |
< |
Adder[] rs = new Adder[n << 1]; |
| 253 |
> |
if (cells == as) { // Expand table |
| 254 |
> |
Cell[] rs = new Cell[n << 1]; |
| 255 |
|
for (int i = 0; i < n; ++i) |
| 256 |
|
rs[i] = as[i]; |
| 257 |
< |
adders = rs; |
| 257 |
> |
cells = rs; |
| 258 |
|
} |
| 259 |
|
} finally { |
| 260 |
|
busy = 0; |
| 266 |
|
h ^= h >>> 17; |
| 267 |
|
h ^= h << 5; |
| 268 |
|
} |
| 269 |
< |
else if (adders == as) { // Try to default-initialize |
| 270 |
< |
Adder[] rs = new Adder[1]; |
| 267 |
< |
rs[0] = new Adder(x); |
| 269 |
> |
else if (busy == 0 && cells == as && |
| 270 |
> |
UNSAFE.compareAndSwapInt(this, busyOffset, 0, 1)) { |
| 271 |
|
boolean init = false; |
| 272 |
< |
while (adders == as) { |
| 273 |
< |
if (UNSAFE.compareAndSwapInt(this, busyOffset, 0, 1)) { |
| 274 |
< |
try { |
| 275 |
< |
if (adders == as) { |
| 276 |
< |
adders = rs; |
| 277 |
< |
init = true; |
| 278 |
< |
} |
| 276 |
< |
} finally { |
| 277 |
< |
busy = 0; |
| 278 |
< |
} |
| 279 |
< |
break; |
| 272 |
> |
try { // Initialize |
| 273 |
> |
if (cells == as) { |
| 274 |
> |
Cell r = new Cell(x); |
| 275 |
> |
Cell[] rs = new Cell[2]; |
| 276 |
> |
rs[h & 1] = r; |
| 277 |
> |
cells = rs; |
| 278 |
> |
init = true; |
| 279 |
|
} |
| 280 |
< |
if (adders != as) |
| 281 |
< |
break; |
| 283 |
< |
Thread.yield(); // Back off |
| 280 |
> |
} finally { |
| 281 |
> |
busy = 0; |
| 282 |
|
} |
| 283 |
|
if (init) |
| 284 |
|
break; |
| 285 |
|
} |
| 286 |
+ |
else { // Lost initialization race |
| 287 |
+ |
long b = base; // Fall back on using base |
| 288 |
+ |
if (UNSAFE.compareAndSwapLong(this, baseOffset, b, b + x)) |
| 289 |
+ |
break; |
| 290 |
+ |
} |
| 291 |
|
} |
| 292 |
|
hc.code = h; // Record index for next time |
| 293 |
|
} |
| 307 |
|
} |
| 308 |
|
|
| 309 |
|
/** |
| 310 |
< |
* Returns an estimate of the current sum. The result is |
| 311 |
< |
* calculated by summing multiple variables, so may not be |
| 312 |
< |
* accurate if updates occur concurrently with this method. |
| 310 |
> |
* Returns the current sum. The result is only guaranteed to be |
| 311 |
> |
* accurate in the absence of concurrent updates. Otherwise, it |
| 312 |
> |
* may fail to reflect one or more updates occuring while |
| 313 |
> |
* calculating the result. |
| 314 |
|
* |
| 315 |
< |
* @return the estimated sum |
| 315 |
> |
* @return the sum |
| 316 |
|
*/ |
| 317 |
|
public long sum() { |
| 318 |
< |
long sum = 0L; |
| 319 |
< |
Adder[] as = adders; |
| 318 |
> |
Cell[] as = cells; |
| 319 |
> |
long sum = base; |
| 320 |
|
if (as != null) { |
| 321 |
|
int n = as.length; |
| 322 |
|
for (int i = 0; i < n; ++i) { |
| 323 |
< |
Adder a = as[i]; |
| 323 |
> |
Cell a = as[i]; |
| 324 |
|
if (a != null) |
| 325 |
|
sum += a.value; |
| 326 |
|
} |
| 329 |
|
} |
| 330 |
|
|
| 331 |
|
/** |
| 332 |
< |
* Resets each of the variables to zero, returning the estimated |
| 333 |
< |
* previous sum. This is effective in fully resetting the sum only |
| 334 |
< |
* if there are no concurrent updates. |
| 335 |
< |
* |
| 336 |
< |
* @return the estimated previous sum |
| 337 |
< |
*/ |
| 338 |
< |
public long reset() { |
| 339 |
< |
long sum = 0L; |
| 340 |
< |
Adder[] as = adders; |
| 332 |
> |
* Resets variables maintaining the sum to zero. This is |
| 333 |
> |
* effective in setting the sum to zero only if there are no |
| 334 |
> |
* concurrent updates. |
| 335 |
> |
*/ |
| 336 |
> |
public void reset() { |
| 337 |
> |
Cell[] as = cells; |
| 338 |
> |
base = 0L; |
| 339 |
> |
if (as != null) { |
| 340 |
> |
int n = as.length; |
| 341 |
> |
for (int i = 0; i < n; ++i) { |
| 342 |
> |
Cell a = as[i]; |
| 343 |
> |
if (a != null) |
| 344 |
> |
a.value = 0L; |
| 345 |
> |
} |
| 346 |
> |
} |
| 347 |
> |
} |
| 348 |
> |
|
| 349 |
> |
/** |
| 350 |
> |
* Equivalent in effect to {@link #sum} followed by {@link |
| 351 |
> |
* #reset}. This method may apply for example during quiescent |
| 352 |
> |
* points between multithreaded computations. If there are |
| 353 |
> |
* updates concurrent with this method, the returned value is |
| 354 |
> |
* <em>not</em> guaranteed to be the final sum occurring before |
| 355 |
> |
* the reset. |
| 356 |
> |
* |
| 357 |
> |
* @return the sum |
| 358 |
> |
*/ |
| 359 |
> |
public long sumThenReset() { |
| 360 |
> |
Cell[] as = cells; |
| 361 |
> |
long sum = base; |
| 362 |
> |
base = 0L; |
| 363 |
|
if (as != null) { |
| 364 |
|
int n = as.length; |
| 365 |
|
for (int i = 0; i < n; ++i) { |
| 366 |
< |
Adder a = as[i]; |
| 366 |
> |
Cell a = as[i]; |
| 367 |
|
if (a != null) { |
| 368 |
|
sum += a.value; |
| 369 |
|
a.value = 0L; |
| 383 |
|
throws IOException, ClassNotFoundException { |
| 384 |
|
s.defaultReadObject(); |
| 385 |
|
busy = 0; |
| 386 |
< |
add(s.readLong()); |
| 386 |
> |
cells = null; |
| 387 |
> |
base = s.readLong(); |
| 388 |
|
} |
| 389 |
|
|
| 390 |
|
// Unsafe mechanics |
| 391 |
|
private static final sun.misc.Unsafe UNSAFE; |
| 392 |
+ |
private static final long baseOffset; |
| 393 |
|
private static final long busyOffset; |
| 394 |
|
private static final long valueOffset; |
| 395 |
|
static { |
| 396 |
|
try { |
| 397 |
|
UNSAFE = getUnsafe(); |
| 398 |
|
Class<?> sk = StripedAdder.class; |
| 399 |
+ |
baseOffset = UNSAFE.objectFieldOffset |
| 400 |
+ |
(sk.getDeclaredField("base")); |
| 401 |
|
busyOffset = UNSAFE.objectFieldOffset |
| 402 |
|
(sk.getDeclaredField("busy")); |
| 403 |
< |
Class<?> ak = Adder.class; |
| 403 |
> |
Class<?> ak = Cell.class; |
| 404 |
|
valueOffset = UNSAFE.objectFieldOffset |
| 405 |
|
(ak.getDeclaredField("value")); |
| 406 |
|
} catch (Exception e) { |
