/*

   BLIS
   An object-based framework for developing high-performance BLAS-like
   libraries.

   Copyright (C) 2014, The University of Texas at Austin
   Copyright (C) 2018 - 2019, Advanced Micro Devices, Inc.

   Redistribution and use in source and binary forms, with or without
   modification, are permitted provided that the following conditions are
   met:
    - Redistributions of source code must retain the above copyright
      notice, this list of conditions and the following disclaimer.
    - Redistributions in binary form must reproduce the above copyright
      notice, this list of conditions and the following disclaimer in the
      documentation and/or other materials provided with the distribution.
    - Neither the name(s) of the copyright holder(s) nor the names of its
      contributors may be used to endorse or promote products derived
      from this software without specific prior written permission.

   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
   HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

*/

#include "blis.h"

#ifdef BLIS_ENABLE_OPENMP

#ifndef BLIS_TREE_BARRIER

// Define the non-tree barrier implementations of the init, cleanup, and
// barrier functions. These are the default unless the tree barrier
// versions are requested at compile-time.

void bli_thrcomm_init_openmp( dim_t n_threads, thrcomm_t* comm )
{
	if ( comm == NULL ) return;
	comm->sent_object = NULL;
	comm->n_threads = n_threads;
	comm->barrier_sense = 0;
	comm->barrier_threads_arrived = 0;
}


void bli_thrcomm_cleanup_openmp( thrcomm_t* comm )
{
	//if ( comm == NULL ) return;
	return;
}

//'Normal' barrier for openmp
//barrier routine taken from art of multicore programming
void bli_thrcomm_barrier_openmp( dim_t t_id, thrcomm_t* comm )
{
#if 0
	if ( comm == NULL || comm->n_threads == 1 )
		return;
	gint_t my_sense = comm->barrier_sense;
	dim_t my_threads_arrived;

	_Pragma( "omp atomic capture" )
		my_threads_arrived = ++(comm->barrier_threads_arrived);

	if ( my_threads_arrived == comm->n_threads )
	{
		comm->barrier_threads_arrived = 0;
		comm->barrier_sense = !comm->barrier_sense;
	}
	else
	{
		volatile gint_t* listener = &comm->barrier_sense;
		while ( *listener == my_sense ) {}
	}
#endif
	bli_thrcomm_barrier_atomic( t_id, comm );
}

#else

// Define the tree barrier implementations of the init, cleanup, and
// barrier functions.

void bli_thrcomm_init_openmp( dim_t n_threads, thrcomm_t* comm )
{
	err_t r_val;

	if ( comm == NULL ) return;
	comm->sent_object = NULL;
	comm->n_threads = n_threads;
	comm->barriers = bli_malloc_intl( sizeof( barrier_t* ) * n_threads, &r_val );
	bli_thrcomm_tree_barrier_create( n_threads, BLIS_TREE_BARRIER_ARITY, comm->barriers, 0 );
}

void bli_thrcomm_cleanup_openmp( thrcomm_t* comm )
{
	if ( comm == NULL ) return;
	for ( dim_t i = 0; i < comm->n_threads; i++ )
	{
	   bli_thrcomm_tree_barrier_free( comm->barriers[i] );
	}
	bli_free_intl( comm->barriers );
}

void bli_thrcomm_barrier_openmp( dim_t t_id, thrcomm_t* comm )
{
	// Return early if the comm is NULL or if there is only one
	// thread participating.
	if ( comm == NULL || comm->n_threads == 1 ) return;

	bli_thrcomm_tree_barrier( comm->barriers[t_id] );
}

// -- Helper functions ---------------------------------------------------------

//Tree barrier used for Intel Xeon Phi
barrier_t* bli_thrcomm_tree_barrier_create( int num_threads, int arity, barrier_t** leaves, int leaf_index )
{
	err_t r_val;

	barrier_t* me = bli_malloc_intl( sizeof( barrier_t ), &r_val );

	me->dad = NULL;
	me->signal = 0;

	// Base Case
	if ( num_threads <= arity )
	{
		//Now must be registered as a leaf
		for ( int i = 0; i < num_threads; i++ )
		{
			leaves[ leaf_index + i ] = me;
		}
		me->count = num_threads;
		me->arity = num_threads;
	}
	else
	{
		// Otherwise this node has children
		int threads_per_kid = num_threads / arity;
		int defecit = num_threads - threads_per_kid * arity;

		for ( int i = 0; i < arity; i++ )
		{
			int threads_this_kid = threads_per_kid;
			if ( i < defecit ) threads_this_kid++;

			barrier_t* kid = bli_thrcomm_tree_barrier_create( threads_this_kid, arity, leaves, leaf_index );
			kid->dad = me;

			leaf_index += threads_this_kid;
		}  
		me->count = arity;
		me->arity = arity;
	}  

	return me;
}

void bli_thrcomm_tree_barrier_free( barrier_t* barrier )
{
	if ( barrier == NULL )
		return;
	barrier->count--;
	if ( barrier->count == 0 )
	{
		bli_thrcomm_tree_barrier_free( barrier->dad );
		bli_free_intl( barrier );
	}
	return;
}

// Use __sync_* builtins (assumed available) if __atomic_* ones are not present.
#ifndef __ATOMIC_RELAXED

#define __ATOMIC_RELAXED
#define __ATOMIC_ACQUIRE
#define __ATOMIC_RELEASE
#define __ATOMIC_ACQ_REL

//#define __atomic_add_fetch( ptr, value, constraint ) __sync_add_and_fetch( ptr, value )
//#define __atomic_fetch_add( ptr, value, constraint ) __sync_fetch_and_add( ptr, value )

#define __atomic_load_n(    ptr,        constraint ) __sync_fetch_and_add( ptr, 0     )
#define __atomic_sub_fetch( ptr, value, constraint ) __sync_sub_and_fetch( ptr, value )
#define __atomic_fetch_xor( ptr, value, constraint ) __sync_fetch_and_xor( ptr, value )

#endif

void bli_thrcomm_tree_barrier( barrier_t* barack )
{
	gint_t my_signal = __atomic_load_n( &barack->signal, __ATOMIC_RELAXED );

	dim_t my_count =
	__atomic_sub_fetch( &barack->count, 1, __ATOMIC_ACQ_REL );

	if ( my_count == 0 )
	{
		if ( barack->dad != NULL )
		{
			bli_thrcomm_tree_barrier( barack->dad );
		}
		barack->count = barack->arity;
		__atomic_fetch_xor( &barack->signal, 1, __ATOMIC_RELEASE );
	}
	else
	{
		while ( __atomic_load_n( &barack->signal, __ATOMIC_ACQUIRE ) == my_signal ) {}
	}
}

#endif

#endif

