final/runtime/src/kmp_taskdeps.cpp - openmp - Git at Google

 /*
  * kmp_taskdeps.cpp
  * $Revision: 42539 $
  * $Date: 2013-07-17 11:20:01 -0500 (Wed, 17 Jul 2013) $
  */


 //===----------------------------------------------------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is dual licensed under the MIT and the University of Illinois Open
 // Source Licenses. See LICENSE.txt for details.
 //
 //===----------------------------------------------------------------------===//


 //#define KMP_SUPPORT_GRAPH_OUTPUT 1

 #include "kmp.h"
 #include "kmp_io.h"
 #include "kmp_wait_release.h"

 #if OMP_40_ENABLED

 //TODO: Improve memory allocation? keep a list of pre-allocated structures? allocate in blocks? re-use list finished list entries?
 //TODO: don't use atomic ref counters for stack-allocated nodes.
 //TODO: find an alternate to atomic refs for heap-allocated nodes?
 //TODO: Finish graph output support
 //TODO: kmp_lock_t seems a tad to big (and heavy weight) for this. Check other runtime locks
 //TODO: Any ITT support needed?

 #ifdef KMP_SUPPORT_GRAPH_OUTPUT
 static kmp_int32 kmp_node_id_seed = 0;
 #endif

 static void
 __kmp_init_node ( kmp_depnode_t *node )
 {
     node->dn.task = NULL; // set to null initially, it will point to the right task once dependences have been processed
     node->dn.successors = NULL;
     __kmp_init_lock(&node->dn.lock);
     node->dn.nrefs = 1; // init creates the first reference to the node
 #ifdef KMP_SUPPORT_GRAPH_OUTPUT
     node->dn.id = KMP_TEST_THEN_INC32(&kmp_node_id_seed);
 #endif
 }

 static inline kmp_depnode_t *
 __kmp_node_ref ( kmp_depnode_t *node )
 {
     KMP_TEST_THEN_INC32(&node->dn.nrefs);
     return node;
 }

 static inline void
 __kmp_node_deref ( kmp_info_t *thread, kmp_depnode_t *node )
 {
     if (!node) return;

     kmp_int32 n = KMP_TEST_THEN_DEC32(&node->dn.nrefs) - 1;
     if ( n == 0 ) {
         KMP_ASSERT(node->dn.nrefs == 0);
 #if USE_FAST_MEMORY
         __kmp_fast_free(thread,node);
 #else
         __kmp_thread_free(thread,node);
 #endif
     }
 }

 #define KMP_ACQUIRE_DEPNODE(gtid,n) __kmp_acquire_lock(&(n)->dn.lock,(gtid))
 #define KMP_RELEASE_DEPNODE(gtid,n) __kmp_release_lock(&(n)->dn.lock,(gtid))

 static void
 __kmp_depnode_list_free ( kmp_info_t *thread, kmp_depnode_list *list );

 static const kmp_int32 kmp_dephash_log2 = 6;
 static const kmp_int32 kmp_dephash_size = (1 << kmp_dephash_log2);

 static inline kmp_int32
 __kmp_dephash_hash ( kmp_intptr_t addr )
 {
     //TODO alternate to try: set = (((Addr64)(addrUsefulBits * 9.618)) % m_num_sets );
     return ((addr >> kmp_dephash_log2) ^ addr) % kmp_dephash_size;
 }

 static kmp_dephash_t *
 __kmp_dephash_create ( kmp_info_t *thread )
 {
     kmp_dephash_t *h;

     kmp_int32 size = kmp_dephash_size * sizeof(kmp_dephash_entry_t) + sizeof(kmp_dephash_t);

 #if USE_FAST_MEMORY
     h = (kmp_dephash_t *) __kmp_fast_allocate( thread, size );
 #else
     h = (kmp_dephash_t *) __kmp_thread_malloc( thread, size );
 #endif

 #ifdef KMP_DEBUG
     h->nelements = 0;
 #endif
     h->buckets = (kmp_dephash_entry **)(h+1);

     for ( kmp_int32 i = 0; i < kmp_dephash_size; i++ )
         h->buckets[i] = 0;

     return h;
 }

 static void
 __kmp_dephash_free ( kmp_info_t *thread, kmp_dephash_t *h )
 {
     for ( kmp_int32 i=0; i < kmp_dephash_size; i++ ) {
         if ( h->buckets[i] ) {
             kmp_dephash_entry_t *next;
             for ( kmp_dephash_entry_t *entry = h->buckets[i]; entry; entry = next ) {
                 next = entry->next_in_bucket;
                 __kmp_depnode_list_free(thread,entry->last_ins);
                 __kmp_node_deref(thread,entry->last_out);
 #if USE_FAST_MEMORY
                 __kmp_fast_free(thread,entry);
 #else
                 __kmp_thread_free(thread,entry);
 #endif
             }
         }
     }
 #if USE_FAST_MEMORY
     __kmp_fast_free(thread,h);
 #else
     __kmp_thread_free(thread,h);
 #endif
 }

 static kmp_dephash_entry *
 __kmp_dephash_find ( kmp_info_t *thread, kmp_dephash_t *h, kmp_intptr_t addr )
 {
     kmp_int32 bucket = __kmp_dephash_hash(addr);

     kmp_dephash_entry_t *entry;
     for ( entry = h->buckets[bucket]; entry; entry = entry->next_in_bucket )
         if ( entry->addr == addr ) break;

     if ( entry == NULL ) {
         // create entry. This is only done by one thread so no locking required
 #if USE_FAST_MEMORY
         entry = (kmp_dephash_entry_t *) __kmp_fast_allocate( thread, sizeof(kmp_dephash_entry_t) );
 #else
         entry = (kmp_dephash_entry_t *) __kmp_thread_malloc( thread, sizeof(kmp_dephash_entry_t) );
 #endif
         entry->addr = addr;
         entry->last_out = NULL;
         entry->last_ins = NULL;
         entry->next_in_bucket = h->buckets[bucket];
         h->buckets[bucket] = entry;
 #ifdef KMP_DEBUG
         h->nelements++;
         if ( entry->next_in_bucket ) h->nconflicts++;
 #endif
     }
     return entry;
 }

 static kmp_depnode_list_t *
 __kmp_add_node ( kmp_info_t *thread, kmp_depnode_list_t *list, kmp_depnode_t *node )
 {
     kmp_depnode_list_t *new_head;

 #if USE_FAST_MEMORY
     new_head = (kmp_depnode_list_t *) __kmp_fast_allocate(thread,sizeof(kmp_depnode_list_t));
 #else
     new_head = (kmp_depnode_list_t *) __kmp_thread_malloc(thread,sizeof(kmp_depnode_list_t));
 #endif

     new_head->node = __kmp_node_ref(node);
     new_head->next = list;

     return new_head;
 }

 static void
 __kmp_depnode_list_free ( kmp_info_t *thread, kmp_depnode_list *list )
 {
     kmp_depnode_list *next;

     for ( ; list ; list = next ) {
         next = list->next;

         __kmp_node_deref(thread,list->node);
 #if USE_FAST_MEMORY
         __kmp_fast_free(thread,list);
 #else
         __kmp_thread_free(thread,list);
 #endif
     }
 }

 static inline void
 __kmp_track_dependence ( kmp_depnode_t *source, kmp_depnode_t *sink )
 {
 #ifdef KMP_SUPPORT_GRAPH_OUTPUT
     kmp_taskdata_t * task_source = KMP_TASK_TO_TASKDATA(source->dn.task);
     kmp_taskdata_t * task_sink = KMP_TASK_TO_TASKDATA(sink->dn.task);    // this can be NULL when if(0) ...

     __kmp_printf("%d(%s) -> %d(%s)\n", source->dn.id, task_source->td_ident->psource, sink->dn.id, task_sink->td_ident->psource);
 #endif
 }

 template< bool filter >
 static inline kmp_int32
 __kmp_process_deps ( kmp_int32 gtid, kmp_depnode_t *node, kmp_dephash_t *hash,
                      bool dep_barrier,kmp_int32 ndeps, kmp_depend_info_t *dep_list)
 {
     KA_TRACE(30, ("__kmp_process_deps<%d>: T#%d processing %d depencies : dep_barrier = %d\n", filter, gtid, ndeps, dep_barrier ) );

     kmp_info_t *thread = __kmp_threads[ gtid ];
     kmp_int32 npredecessors=0;
     for ( kmp_int32 i = 0; i < ndeps ; i++ ) {
         const kmp_depend_info_t * dep = &dep_list[i];

         KMP_DEBUG_ASSERT(dep->flags.in);

         if ( filter && dep->base_addr == 0 ) continue; // skip filtered entries

         kmp_dephash_entry_t *info = __kmp_dephash_find(thread,hash,dep->base_addr);
         kmp_depnode_t *last_out = info->last_out;

         if ( dep->flags.out && info->last_ins ) {
             for ( kmp_depnode_list_t * p = info->last_ins; p; p = p->next ) {
                 kmp_depnode_t * indep = p->node;
                 if ( indep->dn.task ) {
                     KMP_ACQUIRE_DEPNODE(gtid,indep);
                     if ( indep->dn.task ) {
                         __kmp_track_dependence(indep,node);
                         indep->dn.successors = __kmp_add_node(thread, indep->dn.successors, node);
                         KA_TRACE(40,("__kmp_process_deps<%d>: T#%d adding dependence from %p to %p",
                                  filter,gtid, KMP_TASK_TO_TASKDATA(indep->dn.task), KMP_TASK_TO_TASKDATA(node->dn.task)));
                         npredecessors++;
                     }
                     KMP_RELEASE_DEPNODE(gtid,indep);
                 }
             }

             __kmp_depnode_list_free(thread,info->last_ins);
             info->last_ins = NULL;

         } else if ( last_out && last_out->dn.task ) {
             KMP_ACQUIRE_DEPNODE(gtid,last_out);
             if ( last_out->dn.task ) {
                 __kmp_track_dependence(last_out,node);
                 last_out->dn.successors = __kmp_add_node(thread, last_out->dn.successors, node);
                 KA_TRACE(40,("__kmp_process_deps<%d>: T#%d adding dependence from %p to %p",
                              filter,gtid, KMP_TASK_TO_TASKDATA(last_out->dn.task), KMP_TASK_TO_TASKDATA(node->dn.task)));

                 npredecessors++;
             }
             KMP_RELEASE_DEPNODE(gtid,last_out);
         }

         if ( dep_barrier ) {
             // if this is a sync point in the serial sequence, then the previous outputs are guaranteed to be completed after
             // the execution of this task so the previous output nodes can be cleared.
             __kmp_node_deref(thread,last_out);
             info->last_out = NULL;
         } else {
             if ( dep->flags.out ) {
                 __kmp_node_deref(thread,last_out);
                 info->last_out = __kmp_node_ref(node);
             } else
                 info->last_ins = __kmp_add_node(thread, info->last_ins, node);
         }

     }

     KA_TRACE(30, ("__kmp_process_deps<%d>: T#%d found %d predecessors\n", filter, gtid, npredecessors ) );

     return npredecessors;
 }

 #define NO_DEP_BARRIER (false)
 #define DEP_BARRIER (true)

 // returns true if the task has any outstanding dependence
 static bool
 __kmp_check_deps ( kmp_int32 gtid, kmp_depnode_t *node, kmp_task_t *task, kmp_dephash_t *hash, bool dep_barrier,
                    kmp_int32 ndeps, kmp_depend_info_t *dep_list,
                    kmp_int32 ndeps_noalias, kmp_depend_info_t *noalias_dep_list )
 {
     int i;

     kmp_taskdata_t * taskdata = KMP_TASK_TO_TASKDATA(task);
     KA_TRACE(20, ("__kmp_check_deps: T#%d checking dependencies for task %p : %d possibly aliased dependencies, %d non-aliased depedencies : dep_barrier=%d .\n", gtid, taskdata, ndeps, ndeps_noalias, dep_barrier ) );

     // Filter deps in dep_list
     // TODO: Different algorithm for large dep_list ( > 10 ? )
     for ( i = 0; i < ndeps; i ++ ) {
         if ( dep_list[i].base_addr != 0 )
             for ( int j = i+1; j < ndeps; j++ )
                 if ( dep_list[i].base_addr == dep_list[j].base_addr ) {
                     dep_list[i].flags.in |= dep_list[j].flags.in;
                     dep_list[i].flags.out |= dep_list[j].flags.out;
                     dep_list[j].base_addr = 0; // Mark j element as void
                 }
     }

     // doesn't need to be atomic as no other thread is going to be accessing this node just yet
     // npredecessors is set -1 to ensure that none of the releasing tasks queues this task before we have finished processing all the dependencies
     node->dn.npredecessors = -1;

     // used to pack all npredecessors additions into a single atomic operation at the end
     int npredecessors;

     npredecessors = __kmp_process_deps<true>(gtid, node, hash, dep_barrier, ndeps, dep_list);
     npredecessors += __kmp_process_deps<false>(gtid, node, hash, dep_barrier, ndeps_noalias, noalias_dep_list);

     node->dn.task = task;
     KMP_MB();

     // Account for our initial fake value
     npredecessors++;

     // Update predecessors and obtain current value to check if there are still any outstandig dependences (some tasks may have finished while we processed the dependences)
     npredecessors = KMP_TEST_THEN_ADD32(&node->dn.npredecessors, npredecessors) + npredecessors;

     KA_TRACE(20, ("__kmp_check_deps: T#%d found %d predecessors for task %p \n", gtid, npredecessors, taskdata ) );

     // beyond this point the task could be queued (and executed) by a releasing task...
     return npredecessors > 0 ? true : false;
 }

 void
 __kmp_release_deps ( kmp_int32 gtid, kmp_taskdata_t *task )
 {
     kmp_info_t *thread = __kmp_threads[ gtid ];
     kmp_depnode_t *node = task->td_depnode;

     if ( task->td_dephash ) {
         KA_TRACE(40, ("__kmp_realease_deps: T#%d freeing dependencies hash of task %p.\n", gtid, task ) );
         __kmp_dephash_free(thread,task->td_dephash);
     }

     if ( !node ) return;

     KA_TRACE(20, ("__kmp_realease_deps: T#%d notifying succesors of task %p.\n", gtid, task ) );

     KMP_ACQUIRE_DEPNODE(gtid,node);
     node->dn.task = NULL; // mark this task as finished, so no new dependencies are generated
     KMP_RELEASE_DEPNODE(gtid,node);

     kmp_depnode_list_t *next;
     for ( kmp_depnode_list_t *p = node->dn.successors; p; p = next ) {
         kmp_depnode_t *successor = p->node;
         kmp_int32 npredecessors = KMP_TEST_THEN_DEC32(&successor->dn.npredecessors) - 1;

         // successor task can be NULL for wait_depends or because deps are still being processed
         if ( npredecessors == 0 ) {
             KMP_MB();
             if ( successor->dn.task ) {
                 KA_TRACE(20, ("__kmp_realease_deps: T#%d successor %p of %p scheduled for execution.\n", gtid, successor->dn.task, task ) );
                 __kmp_omp_task(gtid,successor->dn.task,false);
             }
         }

         next = p->next;
         __kmp_node_deref(thread,p->node);
 #if USE_FAST_MEMORY
         __kmp_fast_free(thread,p);
 #else
         __kmp_thread_free(thread,p);
 #endif
     }

     __kmp_node_deref(thread,node);

     KA_TRACE(20, ("__kmp_realease_deps: T#%d all successors of %p notified of completation\n", gtid, task ) );
 }

 /*!
 @ingroup TASKING
 @param loc_ref location of the original task directive
 @param gtid Global Thread ID of encountering thread
 @param new_task task thunk allocated by __kmp_omp_task_alloc() for the ''new task''
 @param ndeps Number of depend items with possible aliasing
 @param dep_list List of depend items with possible aliasing
 @param ndeps_noalias Number of depend items with no aliasing
 @param noalias_dep_list List of depend items with no aliasing

 @return Returns either TASK_CURRENT_NOT_QUEUED if the current task was not suspendend and queued, or TASK_CURRENT_QUEUED if it was suspended and queued

 Schedule a non-thread-switchable task with dependences for execution
 */
 kmp_int32
 __kmpc_omp_task_with_deps( ident_t *loc_ref, kmp_int32 gtid, kmp_task_t * new_task,
                             kmp_int32 ndeps, kmp_depend_info_t *dep_list,
                             kmp_int32 ndeps_noalias, kmp_depend_info_t *noalias_dep_list )
 {

     kmp_taskdata_t * new_taskdata = KMP_TASK_TO_TASKDATA(new_task);
     KA_TRACE(10, ("__kmpc_omp_task_with_deps(enter): T#%d loc=%p task=%p\n",
                   gtid, loc_ref, new_taskdata ) );

     kmp_info_t *thread = __kmp_threads[ gtid ];
     kmp_taskdata_t * current_task = thread->th.th_current_task;

     bool serial = current_task->td_flags.team_serial || current_task->td_flags.tasking_ser || current_task->td_flags.final;

     if ( !serial && ( ndeps > 0 || ndeps_noalias > 0 )) {
         /* if no dependencies have been tracked yet, create the dependence hash */
         if ( current_task->td_dephash == NULL )
             current_task->td_dephash = __kmp_dephash_create(thread);

 #if USE_FAST_MEMORY
         kmp_depnode_t *node = (kmp_depnode_t *) __kmp_fast_allocate(thread,sizeof(kmp_depnode_t));
 #else
         kmp_depnode_t *node = (kmp_depnode_t *) __kmp_thread_malloc(thread,sizeof(kmp_depnode_t));
 #endif

         __kmp_init_node(node);
         new_taskdata->td_depnode = node;

         if ( __kmp_check_deps( gtid, node, new_task, current_task->td_dephash, NO_DEP_BARRIER,
                                ndeps, dep_list, ndeps_noalias,noalias_dep_list ) ) {
             KA_TRACE(10, ("__kmpc_omp_task_with_deps(exit): T#%d task had blocking dependencies: "
                   "loc=%p task=%p, return: TASK_CURRENT_NOT_QUEUED\n", gtid, loc_ref,
                   new_taskdata ) );
             return TASK_CURRENT_NOT_QUEUED;
         }
     }

     KA_TRACE(10, ("__kmpc_omp_task_with_deps(exit): T#%d task had no blocking dependencies : "
                   "loc=%p task=%p, transferring to __kmpc_omp_task\n", gtid, loc_ref,
                   new_taskdata ) );

     return __kmpc_omp_task(loc_ref,gtid,new_task);
 }

 /*!
 @ingroup TASKING
 @param loc_ref location of the original task directive
 @param gtid Global Thread ID of encountering thread
 @param ndeps Number of depend items with possible aliasing
 @param dep_list List of depend items with possible aliasing
 @param ndeps_noalias Number of depend items with no aliasing
 @param noalias_dep_list List of depend items with no aliasing

 Blocks the current task until all specifies dependencies have been fulfilled.
 */
 void
 __kmpc_omp_wait_deps ( ident_t *loc_ref, kmp_int32 gtid, kmp_int32 ndeps, kmp_depend_info_t *dep_list,
                        kmp_int32 ndeps_noalias, kmp_depend_info_t *noalias_dep_list )
 {
     KA_TRACE(10, ("__kmpc_omp_wait_deps(enter): T#%d loc=%p\n", gtid, loc_ref) );

     if ( ndeps == 0 && ndeps_noalias == 0 ) {
         KA_TRACE(10, ("__kmpc_omp_wait_deps(exit): T#%d has no dependencies to wait upon : loc=%p\n", gtid, loc_ref) );
         return;
     }

     kmp_info_t *thread = __kmp_threads[ gtid ];
     kmp_taskdata_t * current_task = thread->th.th_current_task;

     // We can return immediately as:
     //   - dependences are not computed in serial teams
     //   - if the dephash is not yet created it means we have nothing to wait for
     if ( current_task->td_flags.team_serial || current_task->td_flags.tasking_ser || current_task->td_flags.final || current_task->td_dephash == NULL ) {
         KA_TRACE(10, ("__kmpc_omp_wait_deps(exit): T#%d has no blocking dependencies : loc=%p\n", gtid, loc_ref) );
         return;
     }

     kmp_depnode_t node;
     __kmp_init_node(&node);

     if (!__kmp_check_deps( gtid, &node, NULL, current_task->td_dephash, DEP_BARRIER,
                            ndeps, dep_list, ndeps_noalias, noalias_dep_list )) {
         KA_TRACE(10, ("__kmpc_omp_wait_deps(exit): T#%d has no blocking dependencies : loc=%p\n", gtid, loc_ref) );
         return;
     }

     int thread_finished = FALSE;
     kmp_flag_32 flag((volatile kmp_uint32 *)&(node.dn.npredecessors), 0U);
     while ( node.dn.npredecessors > 0 ) {
         flag.execute_tasks(thread, gtid, FALSE, &thread_finished,
 #if USE_ITT_BUILD
                            NULL,
 #endif
                            __kmp_task_stealing_constraint );
     }

     KA_TRACE(10, ("__kmpc_omp_wait_deps(exit): T#%d finished waiting : loc=%p\n", gtid, loc_ref) );
 }

 #endif /* OMP_40_ENABLED */
	/*
	* kmp_taskdeps.cpp
	* $Revision: 42539 $
	* $Date: 2013-07-17 11:20:01 -0500 (Wed, 17 Jul 2013) $
	*/


	//===----------------------------------------------------------------------===//
	//
	// The LLVM Compiler Infrastructure
	//
	// This file is dual licensed under the MIT and the University of Illinois Open
	// Source Licenses. See LICENSE.txt for details.
	//
	//===----------------------------------------------------------------------===//


	//#define KMP_SUPPORT_GRAPH_OUTPUT 1

	#include "kmp.h"
	#include "kmp_io.h"
	#include "kmp_wait_release.h"

	#if OMP_40_ENABLED

	//TODO: Improve memory allocation? keep a list of pre-allocated structures? allocate in blocks? re-use list finished list entries?
	//TODO: don't use atomic ref counters for stack-allocated nodes.
	//TODO: find an alternate to atomic refs for heap-allocated nodes?
	//TODO: Finish graph output support
	//TODO: kmp_lock_t seems a tad to big (and heavy weight) for this. Check other runtime locks
	//TODO: Any ITT support needed?

	#ifdef KMP_SUPPORT_GRAPH_OUTPUT
	static kmp_int32 kmp_node_id_seed = 0;
	#endif

	static void
	__kmp_init_node ( kmp_depnode_t *node )
	{
	node->dn.task = NULL; // set to null initially, it will point to the right task once dependences have been processed
	node->dn.successors = NULL;
	__kmp_init_lock(&node->dn.lock);
	node->dn.nrefs = 1; // init creates the first reference to the node
	#ifdef KMP_SUPPORT_GRAPH_OUTPUT
	node->dn.id = KMP_TEST_THEN_INC32(&kmp_node_id_seed);
	#endif
	}

	static inline kmp_depnode_t *
	__kmp_node_ref ( kmp_depnode_t *node )
	{
	KMP_TEST_THEN_INC32(&node->dn.nrefs);
	return node;
	}

	static inline void
	__kmp_node_deref ( kmp_info_t thread, kmp_depnode_t node )
	{
	if (!node) return;

	kmp_int32 n = KMP_TEST_THEN_DEC32(&node->dn.nrefs) - 1;
	if ( n == 0 ) {
	KMP_ASSERT(node->dn.nrefs == 0);
	#if USE_FAST_MEMORY
	__kmp_fast_free(thread,node);
	#else
	__kmp_thread_free(thread,node);
	#endif
	}
	}

	#define KMP_ACQUIRE_DEPNODE(gtid,n) __kmp_acquire_lock(&(n)->dn.lock,(gtid))
	#define KMP_RELEASE_DEPNODE(gtid,n) __kmp_release_lock(&(n)->dn.lock,(gtid))

	static void
	__kmp_depnode_list_free ( kmp_info_t thread, kmp_depnode_list list );

	static const kmp_int32 kmp_dephash_log2 = 6;
	static const kmp_int32 kmp_dephash_size = (1 << kmp_dephash_log2);

	static inline kmp_int32
	__kmp_dephash_hash ( kmp_intptr_t addr )
	{
	//TODO alternate to try: set = (((Addr64)(addrUsefulBits * 9.618)) % m_num_sets );
	return ((addr >> kmp_dephash_log2) ^ addr) % kmp_dephash_size;
	}

	static kmp_dephash_t *
	__kmp_dephash_create ( kmp_info_t *thread )
	{
	kmp_dephash_t *h;

	kmp_int32 size = kmp_dephash_size * sizeof(kmp_dephash_entry_t) + sizeof(kmp_dephash_t);

	#if USE_FAST_MEMORY
	h = (kmp_dephash_t *) __kmp_fast_allocate( thread, size );
	#else
	h = (kmp_dephash_t *) __kmp_thread_malloc( thread, size );
	#endif

	#ifdef KMP_DEBUG
	h->nelements = 0;
	#endif
	h->buckets = (kmp_dephash_entry **)(h+1);

	for ( kmp_int32 i = 0; i < kmp_dephash_size; i++ )
	h->buckets[i] = 0;

	return h;
	}

	static void
	__kmp_dephash_free ( kmp_info_t thread, kmp_dephash_t h )
	{
	for ( kmp_int32 i=0; i < kmp_dephash_size; i++ ) {
	if ( h->buckets[i] ) {
	kmp_dephash_entry_t *next;
	for ( kmp_dephash_entry_t *entry = h->buckets[i]; entry; entry = next ) {
	next = entry->next_in_bucket;
	__kmp_depnode_list_free(thread,entry->last_ins);
	__kmp_node_deref(thread,entry->last_out);
	#if USE_FAST_MEMORY
	__kmp_fast_free(thread,entry);
	#else
	__kmp_thread_free(thread,entry);
	#endif
	}
	}
	}
	#if USE_FAST_MEMORY
	__kmp_fast_free(thread,h);
	#else
	__kmp_thread_free(thread,h);
	#endif
	}

	static kmp_dephash_entry *
	__kmp_dephash_find ( kmp_info_t thread, kmp_dephash_t h, kmp_intptr_t addr )
	{
	kmp_int32 bucket = __kmp_dephash_hash(addr);

	kmp_dephash_entry_t *entry;
	for ( entry = h->buckets[bucket]; entry; entry = entry->next_in_bucket )
	if ( entry->addr == addr ) break;

	if ( entry == NULL ) {
	// create entry. This is only done by one thread so no locking required
	#if USE_FAST_MEMORY
	entry = (kmp_dephash_entry_t *) __kmp_fast_allocate( thread, sizeof(kmp_dephash_entry_t) );
	#else
	entry = (kmp_dephash_entry_t *) __kmp_thread_malloc( thread, sizeof(kmp_dephash_entry_t) );
	#endif
	entry->addr = addr;
	entry->last_out = NULL;
	entry->last_ins = NULL;
	entry->next_in_bucket = h->buckets[bucket];
	h->buckets[bucket] = entry;
	#ifdef KMP_DEBUG
	h->nelements++;
	if ( entry->next_in_bucket ) h->nconflicts++;
	#endif
	}
	return entry;
	}

	static kmp_depnode_list_t *
	__kmp_add_node ( kmp_info_t thread, kmp_depnode_list_t list, kmp_depnode_t *node )
	{
	kmp_depnode_list_t *new_head;

	#if USE_FAST_MEMORY
	new_head = (kmp_depnode_list_t *) __kmp_fast_allocate(thread,sizeof(kmp_depnode_list_t));
	#else
	new_head = (kmp_depnode_list_t *) __kmp_thread_malloc(thread,sizeof(kmp_depnode_list_t));
	#endif

	new_head->node = __kmp_node_ref(node);
	new_head->next = list;

	return new_head;
	}

	static void
	__kmp_depnode_list_free ( kmp_info_t thread, kmp_depnode_list list )
	{
	kmp_depnode_list *next;

	for ( ; list ; list = next ) {
	next = list->next;

	__kmp_node_deref(thread,list->node);
	#if USE_FAST_MEMORY
	__kmp_fast_free(thread,list);
	#else
	__kmp_thread_free(thread,list);
	#endif
	}
	}

	static inline void
	__kmp_track_dependence ( kmp_depnode_t source, kmp_depnode_t sink )
	{
	#ifdef KMP_SUPPORT_GRAPH_OUTPUT
	kmp_taskdata_t * task_source = KMP_TASK_TO_TASKDATA(source->dn.task);
	kmp_taskdata_t * task_sink = KMP_TASK_TO_TASKDATA(sink->dn.task); // this can be NULL when if(0) ...

	__kmp_printf("%d(%s) -> %d(%s)\n", source->dn.id, task_source->td_ident->psource, sink->dn.id, task_sink->td_ident->psource);
	#endif
	}

	template< bool filter >
	static inline kmp_int32
	__kmp_process_deps ( kmp_int32 gtid, kmp_depnode_t node, kmp_dephash_t hash,
	bool dep_barrier,kmp_int32 ndeps, kmp_depend_info_t *dep_list)
	{
	KA_TRACE(30, ("__kmp_process_deps<%d>: T#%d processing %d depencies : dep_barrier = %d\n", filter, gtid, ndeps, dep_barrier ) );

	kmp_info_t *thread = __kmp_threads[ gtid ];
	kmp_int32 npredecessors=0;
	for ( kmp_int32 i = 0; i < ndeps ; i++ ) {
	const kmp_depend_info_t * dep = &dep_list[i];

	KMP_DEBUG_ASSERT(dep->flags.in);

	if ( filter && dep->base_addr == 0 ) continue; // skip filtered entries

	kmp_dephash_entry_t *info = __kmp_dephash_find(thread,hash,dep->base_addr);
	kmp_depnode_t *last_out = info->last_out;

	if ( dep->flags.out && info->last_ins ) {
	for ( kmp_depnode_list_t * p = info->last_ins; p; p = p->next ) {
	kmp_depnode_t * indep = p->node;
	if ( indep->dn.task ) {
	KMP_ACQUIRE_DEPNODE(gtid,indep);
	if ( indep->dn.task ) {
	__kmp_track_dependence(indep,node);
	indep->dn.successors = __kmp_add_node(thread, indep->dn.successors, node);
	KA_TRACE(40,("__kmp_process_deps<%d>: T#%d adding dependence from %p to %p",
	filter,gtid, KMP_TASK_TO_TASKDATA(indep->dn.task), KMP_TASK_TO_TASKDATA(node->dn.task)));
	npredecessors++;
	}
	KMP_RELEASE_DEPNODE(gtid,indep);
	}
	}

	__kmp_depnode_list_free(thread,info->last_ins);
	info->last_ins = NULL;

	} else if ( last_out && last_out->dn.task ) {
	KMP_ACQUIRE_DEPNODE(gtid,last_out);
	if ( last_out->dn.task ) {
	__kmp_track_dependence(last_out,node);
	last_out->dn.successors = __kmp_add_node(thread, last_out->dn.successors, node);
	KA_TRACE(40,("__kmp_process_deps<%d>: T#%d adding dependence from %p to %p",
	filter,gtid, KMP_TASK_TO_TASKDATA(last_out->dn.task), KMP_TASK_TO_TASKDATA(node->dn.task)));

	npredecessors++;
	}
	KMP_RELEASE_DEPNODE(gtid,last_out);
	}

	if ( dep_barrier ) {
	// if this is a sync point in the serial sequence, then the previous outputs are guaranteed to be completed after
	// the execution of this task so the previous output nodes can be cleared.
	__kmp_node_deref(thread,last_out);
	info->last_out = NULL;
	} else {
	if ( dep->flags.out ) {
	__kmp_node_deref(thread,last_out);
	info->last_out = __kmp_node_ref(node);
	} else
	info->last_ins = __kmp_add_node(thread, info->last_ins, node);
	}

	}

	KA_TRACE(30, ("__kmp_process_deps<%d>: T#%d found %d predecessors\n", filter, gtid, npredecessors ) );

	return npredecessors;
	}

	#define NO_DEP_BARRIER (false)
	#define DEP_BARRIER (true)

	// returns true if the task has any outstanding dependence
	static bool
	__kmp_check_deps ( kmp_int32 gtid, kmp_depnode_t node, kmp_task_t task, kmp_dephash_t *hash, bool dep_barrier,
	kmp_int32 ndeps, kmp_depend_info_t *dep_list,
	kmp_int32 ndeps_noalias, kmp_depend_info_t *noalias_dep_list )
	{
	int i;

	kmp_taskdata_t * taskdata = KMP_TASK_TO_TASKDATA(task);
	KA_TRACE(20, ("__kmp_check_deps: T#%d checking dependencies for task %p : %d possibly aliased dependencies, %d non-aliased depedencies : dep_barrier=%d .\n", gtid, taskdata, ndeps, ndeps_noalias, dep_barrier ) );

	// Filter deps in dep_list
	// TODO: Different algorithm for large dep_list ( > 10 ? )
	for ( i = 0; i < ndeps; i ++ ) {
	if ( dep_list[i].base_addr != 0 )
	for ( int j = i+1; j < ndeps; j++ )
	if ( dep_list[i].base_addr == dep_list[j].base_addr ) {
	dep_list[i].flags.in \|= dep_list[j].flags.in;
	dep_list[i].flags.out \|= dep_list[j].flags.out;
	dep_list[j].base_addr = 0; // Mark j element as void
	}
	}

	// doesn't need to be atomic as no other thread is going to be accessing this node just yet
	// npredecessors is set -1 to ensure that none of the releasing tasks queues this task before we have finished processing all the dependencies
	node->dn.npredecessors = -1;

	// used to pack all npredecessors additions into a single atomic operation at the end
	int npredecessors;

	npredecessors = __kmp_process_deps<true>(gtid, node, hash, dep_barrier, ndeps, dep_list);
	npredecessors += __kmp_process_deps<false>(gtid, node, hash, dep_barrier, ndeps_noalias, noalias_dep_list);

	node->dn.task = task;
	KMP_MB();

	// Account for our initial fake value
	npredecessors++;

	// Update predecessors and obtain current value to check if there are still any outstandig dependences (some tasks may have finished while we processed the dependences)
	npredecessors = KMP_TEST_THEN_ADD32(&node->dn.npredecessors, npredecessors) + npredecessors;

	KA_TRACE(20, ("__kmp_check_deps: T#%d found %d predecessors for task %p \n", gtid, npredecessors, taskdata ) );

	// beyond this point the task could be queued (and executed) by a releasing task...
	return npredecessors > 0 ? true : false;
	}

	void
	__kmp_release_deps ( kmp_int32 gtid, kmp_taskdata_t *task )
	{
	kmp_info_t *thread = __kmp_threads[ gtid ];
	kmp_depnode_t *node = task->td_depnode;

	if ( task->td_dephash ) {
	KA_TRACE(40, ("__kmp_realease_deps: T#%d freeing dependencies hash of task %p.\n", gtid, task ) );
	__kmp_dephash_free(thread,task->td_dephash);
	}

	if ( !node ) return;

	KA_TRACE(20, ("__kmp_realease_deps: T#%d notifying succesors of task %p.\n", gtid, task ) );

	KMP_ACQUIRE_DEPNODE(gtid,node);
	node->dn.task = NULL; // mark this task as finished, so no new dependencies are generated
	KMP_RELEASE_DEPNODE(gtid,node);

	kmp_depnode_list_t *next;
	for ( kmp_depnode_list_t *p = node->dn.successors; p; p = next ) {
	kmp_depnode_t *successor = p->node;
	kmp_int32 npredecessors = KMP_TEST_THEN_DEC32(&successor->dn.npredecessors) - 1;

	// successor task can be NULL for wait_depends or because deps are still being processed
	if ( npredecessors == 0 ) {
	KMP_MB();
	if ( successor->dn.task ) {
	KA_TRACE(20, ("__kmp_realease_deps: T#%d successor %p of %p scheduled for execution.\n", gtid, successor->dn.task, task ) );
	__kmp_omp_task(gtid,successor->dn.task,false);
	}
	}

	next = p->next;
	__kmp_node_deref(thread,p->node);
	#if USE_FAST_MEMORY
	__kmp_fast_free(thread,p);
	#else
	__kmp_thread_free(thread,p);
	#endif
	}

	__kmp_node_deref(thread,node);

	KA_TRACE(20, ("__kmp_realease_deps: T#%d all successors of %p notified of completation\n", gtid, task ) );
	}

	/*!
	@ingroup TASKING
	@param loc_ref location of the original task directive
	@param gtid Global Thread ID of encountering thread
	@param new_task task thunk allocated by __kmp_omp_task_alloc() for the ''new task''
	@param ndeps Number of depend items with possible aliasing
	@param dep_list List of depend items with possible aliasing
	@param ndeps_noalias Number of depend items with no aliasing
	@param noalias_dep_list List of depend items with no aliasing

	@return Returns either TASK_CURRENT_NOT_QUEUED if the current task was not suspendend and queued, or TASK_CURRENT_QUEUED if it was suspended and queued

	Schedule a non-thread-switchable task with dependences for execution
	*/
	kmp_int32
	__kmpc_omp_task_with_deps( ident_t loc_ref, kmp_int32 gtid, kmp_task_t new_task,
	kmp_int32 ndeps, kmp_depend_info_t *dep_list,
	kmp_int32 ndeps_noalias, kmp_depend_info_t *noalias_dep_list )
	{

	kmp_taskdata_t * new_taskdata = KMP_TASK_TO_TASKDATA(new_task);
	KA_TRACE(10, ("__kmpc_omp_task_with_deps(enter): T#%d loc=%p task=%p\n",
	gtid, loc_ref, new_taskdata ) );

	kmp_info_t *thread = __kmp_threads[ gtid ];
	kmp_taskdata_t * current_task = thread->th.th_current_task;

	bool serial = current_task->td_flags.team_serial \|\| current_task->td_flags.tasking_ser \|\| current_task->td_flags.final;

	if ( !serial && ( ndeps > 0 \|\| ndeps_noalias > 0 )) {
	/* if no dependencies have been tracked yet, create the dependence hash */
	if ( current_task->td_dephash == NULL )
	current_task->td_dephash = __kmp_dephash_create(thread);

	#if USE_FAST_MEMORY
	kmp_depnode_t node = (kmp_depnode_t ) __kmp_fast_allocate(thread,sizeof(kmp_depnode_t));
	#else
	kmp_depnode_t node = (kmp_depnode_t ) __kmp_thread_malloc(thread,sizeof(kmp_depnode_t));
	#endif

	__kmp_init_node(node);
	new_taskdata->td_depnode = node;

	if ( __kmp_check_deps( gtid, node, new_task, current_task->td_dephash, NO_DEP_BARRIER,
	ndeps, dep_list, ndeps_noalias,noalias_dep_list ) ) {
	KA_TRACE(10, ("__kmpc_omp_task_with_deps(exit): T#%d task had blocking dependencies: "
	"loc=%p task=%p, return: TASK_CURRENT_NOT_QUEUED\n", gtid, loc_ref,
	new_taskdata ) );
	return TASK_CURRENT_NOT_QUEUED;
	}
	}

	KA_TRACE(10, ("__kmpc_omp_task_with_deps(exit): T#%d task had no blocking dependencies : "
	"loc=%p task=%p, transferring to __kmpc_omp_task\n", gtid, loc_ref,
	new_taskdata ) );

	return __kmpc_omp_task(loc_ref,gtid,new_task);
	}

	/*!
	@ingroup TASKING
	@param loc_ref location of the original task directive
	@param gtid Global Thread ID of encountering thread
	@param ndeps Number of depend items with possible aliasing
	@param dep_list List of depend items with possible aliasing
	@param ndeps_noalias Number of depend items with no aliasing
	@param noalias_dep_list List of depend items with no aliasing

	Blocks the current task until all specifies dependencies have been fulfilled.
	*/
	void
	__kmpc_omp_wait_deps ( ident_t loc_ref, kmp_int32 gtid, kmp_int32 ndeps, kmp_depend_info_t dep_list,
	kmp_int32 ndeps_noalias, kmp_depend_info_t *noalias_dep_list )
	{
	KA_TRACE(10, ("__kmpc_omp_wait_deps(enter): T#%d loc=%p\n", gtid, loc_ref) );

	if ( ndeps == 0 && ndeps_noalias == 0 ) {
	KA_TRACE(10, ("__kmpc_omp_wait_deps(exit): T#%d has no dependencies to wait upon : loc=%p\n", gtid, loc_ref) );
	return;
	}

	kmp_info_t *thread = __kmp_threads[ gtid ];
	kmp_taskdata_t * current_task = thread->th.th_current_task;

	// We can return immediately as:
	// - dependences are not computed in serial teams
	// - if the dephash is not yet created it means we have nothing to wait for
	if ( current_task->td_flags.team_serial \|\| current_task->td_flags.tasking_ser \|\| current_task->td_flags.final \|\| current_task->td_dephash == NULL ) {
	KA_TRACE(10, ("__kmpc_omp_wait_deps(exit): T#%d has no blocking dependencies : loc=%p\n", gtid, loc_ref) );
	return;
	}

	kmp_depnode_t node;
	__kmp_init_node(&node);

	if (!__kmp_check_deps( gtid, &node, NULL, current_task->td_dephash, DEP_BARRIER,
	ndeps, dep_list, ndeps_noalias, noalias_dep_list )) {
	KA_TRACE(10, ("__kmpc_omp_wait_deps(exit): T#%d has no blocking dependencies : loc=%p\n", gtid, loc_ref) );
	return;
	}

	int thread_finished = FALSE;
	kmp_flag_32 flag((volatile kmp_uint32 *)&(node.dn.npredecessors), 0U);
	while ( node.dn.npredecessors > 0 ) {
	flag.execute_tasks(thread, gtid, FALSE, &thread_finished,
	#if USE_ITT_BUILD
	NULL,
	#endif
	__kmp_task_stealing_constraint );
	}

	KA_TRACE(10, ("__kmpc_omp_wait_deps(exit): T#%d finished waiting : loc=%p\n", gtid, loc_ref) );
	}

	#endif /* OMP_40_ENABLED */