| 351 |
|
* based on the current thread's Thread.getId(). These hash codes |
| 352 |
|
* have more uniform distribution properties with respect to small |
| 353 |
|
* moduli (here 1-31) than do other simple hashing functions. |
| 354 |
< |
* To return an index between 0 and max, we use a cheap |
| 354 |
> |
* |
| 355 |
> |
* <p>To return an index between 0 and max, we use a cheap |
| 356 |
|
* approximation to a mod operation, that also corrects for bias |
| 357 |
< |
* due to non-power-of-2 remaindering (see {@link Random#nextInt}). |
| 358 |
< |
* Bits of the hashcode are masked with "nbits", the ceiling power |
| 359 |
< |
* of two of table size (looked up in a table packed into three |
| 360 |
< |
* ints). If too large, this is retried after rotating the hash by |
| 361 |
< |
* nbits bits, while forcing new top bit to 0, which guarantees |
| 362 |
< |
* eventual termination (although with a non-random-bias). This |
| 363 |
< |
* requires an average of less than 2 tries for all table sizes, |
| 364 |
< |
* and has a maximum 2% difference from perfectly uniform slot |
| 365 |
< |
* probabilities when applied to all possible hash codes for sizes |
| 366 |
< |
* less than 32. |
| 357 |
> |
* due to non-power-of-2 remaindering (see {@link |
| 358 |
> |
* java.util.Random#nextInt}). Bits of the hashcode are masked |
| 359 |
> |
* with "nbits", the ceiling power of two of table size (looked up |
| 360 |
> |
* in a table packed into three ints). If too large, this is |
| 361 |
> |
* retried after rotating the hash by nbits bits, while forcing new |
| 362 |
> |
* top bit to 0, which guarantees eventual termination (although |
| 363 |
> |
* with a non-random-bias). This requires an average of less than |
| 364 |
> |
* 2 tries for all table sizes, and has a maximum 2% difference |
| 365 |
> |
* from perfectly uniform slot probabilities when applied to all |
| 366 |
> |
* possible hash codes for sizes less than 32. |
| 367 |
|
* |
| 368 |
|
* @return a per-thread-random index, 0 <= index < max |
| 369 |
|
*/ |
| 384 |
|
/** |
| 385 |
|
* Creates a new slot at given index. Called only when the slot |
| 386 |
|
* appears to be null. Relies on double-check using builtin |
| 387 |
< |
* locks, since they rarely contend. This in turn relies on the |
| 387 |
> |
* locks, since they rarely contend. This in turn relies on the |
| 388 |
|
* arena array being declared volatile. |
| 389 |
|
* |
| 390 |
|
* @param index the index to add slot at |
