1 /*------------------------------------------------------------------------
2 Junction: Concurrent data structures in C++
3 Copyright (c) 2016 Jeff Preshing
5 Distributed under the Simplified BSD License.
6 Original location: https://github.com/preshing/junction
8 This software is distributed WITHOUT ANY WARRANTY; without even the
9 implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
10 See the LICENSE file for more information.
11 ------------------------------------------------------------------------*/
13 #ifndef JUNCTION_DETAILS_LEAPFROG_H
14 #define JUNCTION_DETAILS_LEAPFROG_H
16 #include <junction/Core.h>
17 #include <turf/Atomic.h>
18 #include <turf/Mutex.h>
19 #include <turf/ManualResetEvent.h>
20 #include <turf/Util.h>
21 #include <junction/MapTraits.h>
22 #include <turf/Trace.h>
23 #include <turf/Heap.h>
24 #include <junction/SimpleJobCoordinator.h>
25 #include <junction/QSBR.h>
30 TURF_TRACE_DECLARE(LeapFrog, 33)
34 typedef typename Map::Hash Hash;
35 typedef typename Map::Value Value;
36 typedef typename Map::KeyTraits KeyTraits;
37 typedef typename Map::ValueTraits ValueTraits;
39 static const ureg InitialSize = 8;
40 static const ureg TableMigrationUnitSize = 32;
41 static const ureg LinearSearchLimit = 128;
42 static const ureg CellsInUseSample = LinearSearchLimit;
43 TURF_STATIC_ASSERT(LinearSearchLimit > 0 && LinearSearchLimit < 256); // Must fit in CellGroup::links
44 TURF_STATIC_ASSERT(CellsInUseSample > 0 && CellsInUseSample <= LinearSearchLimit); // Limit sample to failed search chain
47 turf::Atomic<Hash> hash;
48 turf::Atomic<Value> value;
52 // Every cell in the table actually represents a bucket of cells, all linked together in a probe chain.
53 // Each cell in the probe chain is located within the table itself.
54 // "deltas" determines the index of the next cell in the probe chain.
55 // The first cell in the chain is the one that was hashed. It may or may not actually belong in the bucket.
56 // The "second" cell in the chain is given by deltas 0 - 3. It's guaranteed to belong in the bucket.
57 // All subsequent cells in the chain is given by deltas 4 - 7. Also guaranteed to belong in the bucket.
58 turf::Atomic<u8> deltas[8];
63 const ureg sizeMask; // a power of two minus one
64 turf::Mutex mutex; // to DCLI the TableMigration (stored in the jobCoordinator)
65 SimpleJobCoordinator jobCoordinator; // makes all blocked threads participate in the migration
67 Table(ureg sizeMask) : sizeMask(sizeMask) {
70 static Table* create(ureg tableSize) {
71 TURF_ASSERT(turf::util::isPowerOf2(tableSize));
72 TURF_ASSERT(tableSize >= 4);
73 ureg numGroups = tableSize >> 2;
74 Table* table = (Table*) TURF_HEAP.alloc(sizeof(Table) + sizeof(CellGroup) * numGroups);
75 new (table) Table(tableSize - 1);
76 for (ureg i = 0; i < numGroups; i++) {
77 CellGroup* group = table->getCellGroups() + i;
78 for (ureg j = 0; j < 4; j++) {
79 group->deltas[j].storeNonatomic(0);
80 group->deltas[j + 4].storeNonatomic(0);
81 group->cells[j].hash.storeNonatomic(KeyTraits::NullHash);
82 group->cells[j].value.storeNonatomic(Value(ValueTraits::NullValue));
89 this->Table::~Table();
93 CellGroup* getCellGroups() const {
94 return (CellGroup*) (this + 1);
97 ureg getNumMigrationUnits() const {
98 return sizeMask / TableMigrationUnitSize + 1;
102 class TableMigration : public SimpleJobCoordinator::Job {
106 turf::Atomic<ureg> sourceIndex;
110 Table* m_destination;
111 turf::Atomic<ureg> m_workerStatus; // number of workers + end flag
112 turf::Atomic<bool> m_overflowed;
113 turf::Atomic<sreg> m_unitsRemaining;
116 TableMigration(Map& map) : m_map(map) {
119 static TableMigration* create(Map& map, ureg numSources) {
120 TableMigration* migration =
121 (TableMigration*) TURF_HEAP.alloc(sizeof(TableMigration) + sizeof(TableMigration::Source) * numSources);
122 new (migration) TableMigration(map);
123 migration->m_workerStatus.storeNonatomic(0);
124 migration->m_overflowed.storeNonatomic(false);
125 migration->m_unitsRemaining.storeNonatomic(0);
126 migration->m_numSources = numSources;
127 // Caller is responsible for filling in sources & destination
131 virtual ~TableMigration() TURF_OVERRIDE {
135 // Destroy all source tables.
136 for (ureg i = 0; i < m_numSources; i++)
137 if (getSources()[i].table)
138 getSources()[i].table->destroy();
139 // Delete the migration object itself.
140 this->TableMigration::~TableMigration();
141 TURF_HEAP.free(this);
144 Source* getSources() const {
145 return (Source*) (this + 1);
148 bool migrateRange(Table* srcTable, ureg startIdx);
149 virtual void run() TURF_OVERRIDE;
152 static Cell* find(Hash hash, Table* table) {
153 TURF_TRACE(LeapFrog, 0, "[find] called", uptr(table), hash);
155 TURF_ASSERT(hash != KeyTraits::NullHash);
156 ureg sizeMask = table->sizeMask;
157 // Optimistically check hashed cell even though it might belong to another bucket
158 ureg idx = hash & sizeMask;
159 CellGroup* group = table->getCellGroups() + (idx >> 2);
160 Cell* cell = group->cells + (idx & 3);
161 Hash probeHash = cell->hash.load(turf::Relaxed);
162 if (probeHash == hash) {
163 TURF_TRACE(LeapFrog, 1, "[find] found existing cell optimistically", uptr(table), idx);
165 } else if (probeHash == KeyTraits::NullHash) {
168 // Follow probe chain for our bucket
169 u8 delta = group->deltas[idx & 3].load(turf::Relaxed);
171 idx = (idx + delta) & sizeMask;
172 group = table->getCellGroups() + (idx >> 2);
173 cell = group->cells + (idx & 3);
174 Hash probeHash = cell->hash.load(turf::Relaxed);
175 // Note: probeHash might actually be NULL due to memory reordering of a concurrent insert,
176 // but we don't check for it. We just follow the probe chain.
177 if (probeHash == hash) {
178 TURF_TRACE(LeapFrog, 2, "[find] found existing cell", uptr(table), idx);
181 delta = group->deltas[(idx & 3) + 4].load(turf::Relaxed);
183 // End of probe chain, not found
187 // FIXME: Possible optimization: Dedicated insert for migration? It wouldn't check for InsertResult_AlreadyFound.
188 enum InsertResult { InsertResult_AlreadyFound, InsertResult_InsertedNew, InsertResult_Overflow };
189 static InsertResult insert(Hash hash, Table* table, Cell*& cell, ureg& overflowIdx) {
190 TURF_TRACE(LeapFrog, 3, "[insert] called", uptr(table), hash);
192 TURF_ASSERT(hash != KeyTraits::NullHash);
193 ureg sizeMask = table->sizeMask;
194 ureg idx = ureg(hash);
196 // Check hashed cell first, though it may not even belong to the bucket.
197 CellGroup* group = table->getCellGroups() + ((idx & sizeMask) >> 2);
198 cell = group->cells + (idx & 3);
199 Hash probeHash = cell->hash.load(turf::Relaxed);
200 if (probeHash == KeyTraits::NullHash) {
201 if (cell->hash.compareExchangeStrong(probeHash, hash, turf::Relaxed)) {
202 TURF_TRACE(LeapFrog, 4, "[insert] reserved first cell", uptr(table), idx);
203 // There are no links to set. We're done.
204 return InsertResult_InsertedNew;
206 TURF_TRACE(LeapFrog, 5, "[insert] race to reserve first cell", uptr(table), idx);
207 // Fall through to check if it was the same hash...
210 if (probeHash == hash) {
211 TURF_TRACE(LeapFrog, 6, "[insert] found in first cell", uptr(table), idx);
212 return InsertResult_AlreadyFound;
215 // Follow the link chain for this bucket.
216 ureg maxIdx = idx + sizeMask;
218 turf::Atomic<u8>* prevLink;
221 prevLink = group->deltas + ((idx & 3) + linkLevel);
223 u8 probeDelta = prevLink->load(turf::Relaxed);
226 // Check the hash for this cell.
227 group = table->getCellGroups() + ((idx & sizeMask) >> 2);
228 cell = group->cells + (idx & 3);
229 probeHash = cell->hash.load(turf::Relaxed);
230 if (probeHash == KeyTraits::NullHash) {
231 // Cell was linked, but hash is not visible yet.
232 // We could avoid this case (and guarantee it's visible) using acquire & release, but instead,
233 // just poll until it becomes visible.
234 TURF_TRACE(LeapFrog, 7, "[insert] race to read hash", uptr(table), idx);
236 probeHash = cell->hash.load(turf::Acquire);
237 } while (probeHash == KeyTraits::NullHash);
239 TURF_ASSERT(((probeHash ^ hash) & sizeMask) == 0); // Only hashes in same bucket can be linked
240 if (probeHash == hash) {
241 TURF_TRACE(LeapFrog, 8, "[insert] found in probe chain", uptr(table), idx);
242 return InsertResult_AlreadyFound;
245 // Reached the end of the link chain for this bucket.
246 // Switch to linear probing until we reserve a new cell or find a late-arriving cell in the same bucket.
247 ureg prevLinkIdx = idx;
248 TURF_ASSERT(sreg(maxIdx - idx) >= 0); // Nobody would have linked an idx that's out of range.
249 ureg linearProbesRemaining = turf::util::min(maxIdx - idx, LinearSearchLimit);
250 while (linearProbesRemaining-- > 0) {
252 group = table->getCellGroups() + ((idx & sizeMask) >> 2);
253 cell = group->cells + (idx & 3);
254 probeHash = cell->hash.load(turf::Relaxed);
255 if (probeHash == KeyTraits::NullHash) {
256 // It's an empty cell. Try to reserve it.
257 if (cell->hash.compareExchangeStrong(probeHash, hash, turf::Relaxed)) {
258 // Success. We've reserved the cell. Link it to previous cell in same bucket.
259 TURF_TRACE(LeapFrog, 9, "[insert] reserved cell", uptr(table), idx);
260 TURF_ASSERT(probeDelta == 0);
261 u8 desiredDelta = idx - prevLinkIdx;
262 #if TURF_WITH_ASSERTS
263 probeDelta = prevLink->exchange(desiredDelta, turf::Relaxed);
264 TURF_ASSERT(probeDelta == 0 || probeDelta == desiredDelta);
266 prevLink->store(desiredDelta, turf::Relaxed);
268 return InsertResult_InsertedNew;
270 TURF_TRACE(LeapFrog, 10, "[insert] race to reserve cell", uptr(table), idx);
271 // Fall through to check if it's the same hash...
274 Hash x = (probeHash ^ hash);
275 // Check for same hash.
277 TURF_TRACE(LeapFrog, 11, "[insert] found outside probe chain", uptr(table), idx);
278 return InsertResult_AlreadyFound;
280 // Check for same bucket.
281 if ((x & sizeMask) == 0) {
282 TURF_TRACE(LeapFrog, 12, "[insert] found late-arriving cell in same bucket", uptr(table), idx);
283 // Attempt to set the link on behalf of the late-arriving cell.
284 // This is usually redundant, but if we don't attempt to set the late-arriving cell's link here,
285 // there's no guarantee that our own link chain will be well-formed by the time this function returns.
286 // (Indeed, subsequent lookups sometimes failed during testing, for this exact reason.)
287 u8 desiredDelta = idx - prevLinkIdx;
288 #if TURF_WITH_ASSERTS
289 probeDelta = prevLink->exchange(desiredDelta, turf::Relaxed);
290 TURF_ASSERT(probeDelta == 0 || probeDelta == desiredDelta);
292 TURF_TRACE(LeapFrog, 13, "[insert] set link on behalf of late-arriving cell", uptr(table), idx);
294 prevLink->store(desiredDelta, turf::Relaxed);
296 goto followLink; // Try to follow link chain for the bucket again.
298 // Continue linear search...
300 // Table is too full to insert.
301 overflowIdx = idx + 1;
302 TURF_TRACE(LeapFrog, 14, "[insert] overflow", uptr(table), overflowIdx);
303 return InsertResult_Overflow;
308 static void beginTableMigrationToSize(Map& map, Table* table, ureg nextTableSize) {
309 // Create new migration by DCLI.
310 TURF_TRACE(LeapFrog, 15, "[beginTableMigrationToSize] called", 0, 0);
311 SimpleJobCoordinator::Job* job = table->jobCoordinator.loadConsume();
313 TURF_TRACE(LeapFrog, 16, "[beginTableMigrationToSize] new migration already exists", 0, 0);
315 turf::LockGuard<turf::Mutex> guard(table->mutex);
316 job = table->jobCoordinator.loadConsume(); // Non-atomic would be sufficient, but that's OK.
318 TURF_TRACE(LeapFrog, 17, "[beginTableMigrationToSize] new migration already exists (double-checked)", 0, 0);
320 // Create new migration.
321 TableMigration* migration = TableMigration::create(map, 1);
322 migration->m_unitsRemaining.storeNonatomic(table->getNumMigrationUnits());
323 migration->getSources()[0].table = table;
324 migration->getSources()[0].sourceIndex.storeNonatomic(0);
325 migration->m_destination = Table::create(nextTableSize);
326 // Publish the new migration.
327 table->jobCoordinator.storeRelease(migration);
332 static void beginTableMigration(Map& map, Table* table, ureg overflowIdx) {
333 // Estimate number of cells in use based on a small sample.
334 ureg sizeMask = table->sizeMask;
335 ureg idx = overflowIdx - CellsInUseSample;
337 for (ureg linearProbesRemaining = CellsInUseSample; linearProbesRemaining > 0; linearProbesRemaining--) {
338 CellGroup* group = table->getCellGroups() + ((idx & sizeMask) >> 2);
339 Cell* cell = group->cells + (idx & 3);
340 Value value = cell->value.load(turf::Relaxed);
341 if (value == Value(ValueTraits::Redirect)) {
342 // Another thread kicked off the jobCoordinator. The caller will participate upon return.
343 TURF_TRACE(LeapFrog, 18, "[beginTableMigration] redirected while determining table size", 0, 0);
346 if (value != Value(ValueTraits::NullValue))
350 float inUseRatio = float(inUseCells) / CellsInUseSample;
351 float estimatedInUse = (sizeMask + 1) * inUseRatio;
352 ureg nextTableSize = turf::util::roundUpPowerOf2(ureg(estimatedInUse * 2));
353 beginTableMigrationToSize(map, table, nextTableSize);
358 bool LeapFrog<Map>::TableMigration::migrateRange(Table* srcTable, ureg startIdx) {
359 ureg srcSizeMask = srcTable->sizeMask;
360 ureg endIdx = turf::util::min(startIdx + TableMigrationUnitSize, srcSizeMask + 1);
361 // Iterate over source range.
362 for (ureg srcIdx = startIdx; srcIdx < endIdx; srcIdx++) {
363 CellGroup* srcGroup = srcTable->getCellGroups() + ((srcIdx & srcSizeMask) >> 2);
364 Cell* srcCell = srcGroup->cells + (srcIdx & 3);
367 // Fetch the srcHash and srcValue.
369 srcHash = srcCell->hash.load(turf::Relaxed);
370 if (srcHash == KeyTraits::NullHash) {
371 // An unused cell. Try to put a Redirect marker in its value.
373 srcCell->value.compareExchange(Value(ValueTraits::NullValue), Value(ValueTraits::Redirect), turf::Relaxed);
374 if (srcValue == Value(ValueTraits::Redirect)) {
375 // srcValue is already marked Redirect due to previous incomplete migration.
376 TURF_TRACE(LeapFrog, 19, "[migrateRange] empty cell already redirected", uptr(srcTable), srcIdx);
379 if (srcValue == Value(ValueTraits::NullValue))
380 break; // Redirect has been placed. Break inner loop, continue outer loop.
381 TURF_TRACE(LeapFrog, 20, "[migrateRange] race to insert key", uptr(srcTable), srcIdx);
382 // Otherwise, somebody just claimed the cell. Read srcHash again...
384 // Check for deleted/uninitialized value.
385 srcValue = srcCell->value.load(turf::Relaxed);
386 if (srcValue == Value(ValueTraits::NullValue)) {
387 // Try to put a Redirect marker.
388 if (srcCell->value.compareExchangeStrong(srcValue, Value(ValueTraits::Redirect), turf::Relaxed))
389 break; // Redirect has been placed. Break inner loop, continue outer loop.
390 TURF_TRACE(LeapFrog, 21, "[migrateRange] race to insert value", uptr(srcTable), srcIdx);
391 if (srcValue == Value(ValueTraits::Redirect)) {
392 // FIXME: I don't think this will happen. Investigate & change to assert
393 TURF_TRACE(LeapFrog, 22, "[migrateRange] race inserted Redirect", uptr(srcTable), srcIdx);
396 } else if (srcValue == Value(ValueTraits::Redirect)) {
397 // srcValue is already marked Redirect due to previous incomplete migration.
398 TURF_TRACE(LeapFrog, 23, "[migrateRange] in-use cell already redirected", uptr(srcTable), srcIdx);
402 // We've got a key/value pair to migrate.
403 // Reserve a destination cell in the destination.
404 TURF_ASSERT(srcHash != KeyTraits::NullHash);
405 TURF_ASSERT(srcValue != Value(ValueTraits::NullValue));
406 TURF_ASSERT(srcValue != Value(ValueTraits::Redirect));
409 InsertResult result = insert(srcHash, m_destination, dstCell, overflowIdx);
410 // During migration, a hash can only exist in one place among all the source tables,
411 // and it is only migrated by one thread. Therefore, the hash will never already exist
412 // in the destination table:
413 TURF_ASSERT(result != InsertResult_AlreadyFound);
414 if (result == InsertResult_Overflow) {
415 // Destination overflow.
416 // This can happen for several reasons. For example, the source table could have
417 // existed of all deleted cells when it overflowed, resulting in a small destination
418 // table size, but then another thread could re-insert all the same hashes
419 // before the migration completed.
420 // Caller will cancel the current migration and begin a new one.
423 // Migrate the old value to the new cell.
425 // Copy srcValue to the destination.
426 dstCell->value.store(srcValue, turf::Relaxed);
427 // Try to place a Redirect marker in srcValue.
428 Value doubleCheckedSrcValue =
429 srcCell->value.compareExchange(srcValue, Value(ValueTraits::Redirect), turf::Relaxed);
430 TURF_ASSERT(doubleCheckedSrcValue !=
431 Value(ValueTraits::Redirect)); // Only one thread can redirect a cell at a time.
432 if (doubleCheckedSrcValue == srcValue) {
433 // No racing writes to the src. We've successfully placed the Redirect marker.
434 // srcValue was non-NULL when we decided to migrate it, but it may have changed to NULL
435 // by a late-arriving erase.
436 if (srcValue == Value(ValueTraits::NullValue))
437 TURF_TRACE(LeapFrog, 24, "[migrateRange] racing update was erase", uptr(srcTable), srcIdx);
440 // There was a late-arriving write (or erase) to the src. Migrate the new value and try again.
441 TURF_TRACE(LeapFrog, 25, "[migrateRange] race to update migrated value", uptr(srcTable), srcIdx);
442 srcValue = doubleCheckedSrcValue;
444 // Cell successfully migrated. Proceed to next source cell.
449 // Range has been migrated successfully.
454 void LeapFrog<Map>::TableMigration::run() {
455 // Conditionally increment the shared # of workers.
456 ureg probeStatus = m_workerStatus.load(turf::Relaxed);
458 if (probeStatus & 1) {
459 // End flag is already set, so do nothing.
460 TURF_TRACE(LeapFrog, 26, "[TableMigration::run] already ended", uptr(this), 0);
463 } while (!m_workerStatus.compareExchangeWeak(probeStatus, probeStatus + 2, turf::Relaxed, turf::Relaxed));
464 // # of workers has been incremented, and the end flag is clear.
465 TURF_ASSERT((probeStatus & 1) == 0);
467 // Iterate over all source tables.
468 for (ureg s = 0; s < m_numSources; s++) {
469 Source& source = getSources()[s];
470 // Loop over all migration units in this source table.
472 if (m_workerStatus.load(turf::Relaxed) & 1) {
473 TURF_TRACE(LeapFrog, 27, "[TableMigration::run] detected end flag set", uptr(this), 0);
476 ureg startIdx = source.sourceIndex.fetchAdd(TableMigrationUnitSize, turf::Relaxed);
477 if (startIdx >= source.table->sizeMask + 1)
478 break; // No more migration units in this table. Try next source table.
479 bool overflowed = !migrateRange(source.table, startIdx);
481 // *** FAILED MIGRATION ***
482 // TableMigration failed due to destination table overflow.
483 // No other thread can declare the migration successful at this point, because *this* unit will never complete,
484 // hence m_unitsRemaining won't reach zero.
485 // However, multiple threads can independently detect a failed migration at the same time.
486 TURF_TRACE(LeapFrog, 28, "[TableMigration::run] destination overflow", uptr(source.table), uptr(startIdx));
487 // The reason we store overflowed in a shared variable is because we can must flush all the worker threads before
488 // we can safely deal with the overflow. Therefore, the thread that detects the failure is often different from
490 // that deals with it.
491 bool oldOverflowed = m_overflowed.exchange(overflowed, turf::Relaxed);
493 TURF_TRACE(LeapFrog, 29, "[TableMigration::run] race to set m_overflowed", uptr(overflowed),
494 uptr(oldOverflowed));
495 m_workerStatus.fetchOr(1, turf::Relaxed);
498 sreg prevRemaining = m_unitsRemaining.fetchSub(1, turf::Relaxed);
499 TURF_ASSERT(prevRemaining > 0);
500 if (prevRemaining == 1) {
501 // *** SUCCESSFUL MIGRATION ***
502 // That was the last chunk to migrate.
503 m_workerStatus.fetchOr(1, turf::Relaxed);
508 TURF_TRACE(LeapFrog, 30, "[TableMigration::run] out of migration units", uptr(this), 0);
511 // Decrement the shared # of workers.
512 probeStatus = m_workerStatus.fetchSub(
513 2, turf::AcquireRelease); // AcquireRelease makes all previous writes visible to the last worker thread.
514 if (probeStatus >= 4) {
515 // There are other workers remaining. Return here so that only the very last worker will proceed.
516 TURF_TRACE(LeapFrog, 31, "[TableMigration::run] not the last worker", uptr(this), uptr(probeStatus));
520 // We're the very last worker thread.
521 // Perform the appropriate post-migration step depending on whether the migration succeeded or failed.
522 TURF_ASSERT(probeStatus == 3);
523 bool overflowed = m_overflowed.loadNonatomic(); // No racing writes at this point
525 // The migration succeeded. This is the most likely outcome. Publish the new subtree.
526 m_map.publishTableMigration(this);
527 // End the jobCoodinator.
528 getSources()[0].table->jobCoordinator.end();
530 // The migration failed due to the overflow of the destination table.
531 Table* origTable = getSources()[0].table;
532 turf::LockGuard<turf::Mutex> guard(origTable->mutex);
533 SimpleJobCoordinator::Job* checkedJob = origTable->jobCoordinator.loadConsume();
534 if (checkedJob != this) {
535 TURF_TRACE(LeapFrog, 32, "[TableMigration::run] a new TableMigration was already started", uptr(origTable),
538 TableMigration* migration = TableMigration::create(m_map, m_numSources + 1);
539 // Double the destination table size.
540 migration->m_destination = Table::create((m_destination->sizeMask + 1) * 2);
541 // Transfer source tables to the new migration.
542 for (ureg i = 0; i < m_numSources; i++) {
543 migration->getSources()[i].table = getSources()[i].table;
544 getSources()[i].table = NULL;
545 migration->getSources()[i].sourceIndex.storeNonatomic(0);
547 migration->getSources()[m_numSources].table = m_destination;
548 migration->getSources()[m_numSources].sourceIndex.storeNonatomic(0);
549 // Calculate total number of migration units to move.
550 ureg unitsRemaining = 0;
551 for (ureg s = 0; s < migration->m_numSources; s++)
552 unitsRemaining += migration->getSources()[s].table->getNumMigrationUnits();
553 migration->m_unitsRemaining.storeNonatomic(unitsRemaining);
554 // Publish the new migration.
555 origTable->jobCoordinator.storeRelease(migration);
559 // We're done with this TableMigration. Queue it for GC.
560 DefaultQSBR.enqueue(&TableMigration::destroy, this);
563 } // namespace details
564 } // namespace junction
566 #endif // JUNCTION_DETAILS_LEAPFROG_H