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Kokkos_Spinwait.cpp
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Sat, Aug 10, 22:31

Kokkos_Spinwait.cpp
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/*
//@HEADER
// ************************************************************************
//
// Kokkos v. 2.0
// Copyright (2014) Sandia Corporation
//
// Under the terms of Contract DE-AC04-94AL85000 with Sandia Corporation,
// the U.S. Government retains certain rights in this software.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// 1. Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//
// 2. 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.
//
// 3. Neither the name of the Corporation nor the names of the
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY SANDIA CORPORATION "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 SANDIA CORPORATION OR THE
// 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.
//
// Questions? Contact H. Carter Edwards (hcedwar@sandia.gov)
//
// ************************************************************************
//@HEADER
*/
#include <Kokkos_Macros.hpp>
#if defined( KOKKOS_ACTIVE_EXECUTION_MEMORY_SPACE_HOST )
#include <Kokkos_Atomic.hpp>
#include <impl/Kokkos_Spinwait.hpp>
#include <impl/Kokkos_BitOps.hpp>
#if defined( KOKKOS_ENABLE_STDTHREAD )
#include <thread>
#elif !defined( _WIN32 )
#include <sched.h>
#include <time.h>
#else
#include <process.h>
#include <winsock2.h>
#include <windows.h>
#endif
/*--------------------------------------------------------------------------*/
namespace Kokkos {
namespace Impl {
namespace {
void host_thread_yield( const uint32_t i , const int force_yield )
{
static constexpr uint32_t sleep_limit = 1 << 13 ;
static constexpr uint32_t yield_limit = 1 << 12 ;
const int c = Kokkos::Impl::bit_scan_reverse(i);
if ( sleep_limit < i ) {
// Attempt to put the thread to sleep for 'c' milliseconds
#if defined( KOKKOS_ENABLE_STDTHREAD )
std::this_thread::sleep_for( std::chrono::nanoseconds( c * 1000 ) )
#elif !defined( _WIN32 )
timespec req ;
req.tv_sec = 0 ;
req.tv_nsec = 1000 * c ;
nanosleep( &req, nullptr );
#else /* defined( _WIN32 ) IS Microsoft Windows */
Sleep(c);
#endif
}
else if ( force_yield || yield_limit < i ) {
// Attempt to yield thread resources to runtime
#if defined( KOKKOS_ENABLE_STDTHREAD )
std::this_thread::yield();
#elif !defined( _WIN32 )
sched_yield();
#else /* defined( _WIN32 ) IS Microsoft Windows */
YieldProcessor();
#endif
}
#if defined( KOKKOS_ENABLE_ASM )
else if ( (1u<<4) < i ) {
// Insert a few no-ops to quiet the thread:
for ( int k = 0 ; k < c ; ++k ) {
#if defined( __amd64 ) || defined( __amd64__ ) || \
defined( __x86_64 ) || defined( __x86_64__ )
#if !defined( _WIN32 ) /* IS NOT Microsoft Windows */
asm volatile( "nop\n" );
#else
__asm__ __volatile__( "nop\n" );
#endif
#elif defined(__PPC64__)
asm volatile( "nop\n" );
#endif
}
}
{
// Insert memory pause
#if defined( __amd64 ) || defined( __amd64__ ) || \
defined( __x86_64 ) || defined( __x86_64__ )
#if !defined( _WIN32 ) /* IS NOT Microsoft Windows */
asm volatile( "pause\n":::"memory" );
#else
__asm__ __volatile__( "pause\n":::"memory" );
#endif
#elif defined(__PPC64__)
asm volatile( "or 27, 27, 27" ::: "memory" );
#endif
}
#endif /* defined( KOKKOS_ENABLE_ASM ) */
}
}}} // namespace Kokkos::Impl::{anonymous}
/*--------------------------------------------------------------------------*/
namespace Kokkos {
namespace Impl {
void spinwait_while_equal( volatile int32_t & flag , const int32_t value )
{
Kokkos::store_fence();
uint32_t i = 0 ; while( value == flag ) host_thread_yield(++i,0);
Kokkos::load_fence();
}
void spinwait_until_equal( volatile int32_t & flag , const int32_t value )
{
Kokkos::store_fence();
uint32_t i = 0 ; while( value != flag ) host_thread_yield(++i,0);
Kokkos::load_fence();
}
void spinwait_while_equal( volatile int64_t & flag , const int64_t value )
{
Kokkos::store_fence();
uint32_t i = 0 ; while( value == flag ) host_thread_yield(++i,0);
Kokkos::load_fence();
}
void spinwait_until_equal( volatile int64_t & flag , const int64_t value )
{
Kokkos::store_fence();
uint32_t i = 0 ; while( value != flag ) host_thread_yield(++i,0);
Kokkos::load_fence();
}
void yield_while_equal( volatile int32_t & flag , const int32_t value )
{
Kokkos::store_fence();
uint32_t i = 0 ; while( value == flag ) host_thread_yield(++i,1);
Kokkos::load_fence();
}
void yield_until_equal( volatile int32_t & flag , const int32_t value )
{
Kokkos::store_fence();
uint32_t i = 0 ; while( value != flag ) host_thread_yield(++i,1);
Kokkos::load_fence();
}
void yield_while_equal( volatile int64_t & flag , const int64_t value )
{
Kokkos::store_fence();
uint32_t i = 0 ; while( value == flag ) host_thread_yield(++i,1);
Kokkos::load_fence();
}
void yield_until_equal( volatile int64_t & flag , const int64_t value )
{
Kokkos::store_fence();
uint32_t i = 0 ; while( value != flag ) host_thread_yield(++i,1);
Kokkos::load_fence();
}
} /* namespace Impl */
} /* namespace Kokkos */
#else
void KOKKOS_CORE_SRC_IMPL_SPINWAIT_PREVENT_LINK_ERROR() {}
#endif

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