ElevatorLinear.c

#include <stdbool.h>

//======================================================

static TYPE PAD1 CALIGN __attribute__(( unused ));		// protect further false sharing
static VTYPE fast CALIGN;
#ifndef CAS
static VTYPE * b CALIGN, x CALIGN, y CALIGN;
#endif // ! CAS
static TYPE PAD2 CALIGN __attribute__(( unused ));		// protect further false sharing

#ifdef CAS

#define trylock( x ) Cas( (fast), false, true )

#elif defined( WCasBL )

static inline bool trylock( TYPE id ) {					// based on Burns-Lamport algorithm
	b[id] = true;
	Fence();											// force store before more loads
	for ( typeof(id) thr = 0; thr < id; thr += 1 ) {
		if ( FASTPATH( b[thr] ) ) {
			b[id] = false;
			return false ;
		} // if
	} // for
	for ( typeof(id) thr = id + 1; thr < N; thr += 1 ) {
		await( ! b[thr] );
	} // for
	bool leader;
	if ( ! fast ) { fast = true; leader = true; }
	else leader = false;
	b[id] = false;
	return leader;
} // WCas

#elif defined( WCasLF )

static inline bool trylock( TYPE id ) {					// based on Lamport-Fast algorithm
	b[id] = true;
	x = id;
	Fence();											// force store before more loads
	if ( FASTPATH( y != N ) ) {
		b[id] = false;
		return false;
	} // if
	y = id;
	Fence();											// force store before more loads
	if ( FASTPATH( x != id ) ) {
		b[id] = false;
		Fence();										// OPTIONAL, force store before more loads
		for ( typeof(N) k = 0; k < N; k += 1 )
			await( ! b[k] );
		if ( FASTPATH( y != id ) ) return false;
	} // if
	bool leader;
	if ( ! fast ) { fast = true; leader = true; }
	else leader = false;
	y = N;
	b[id] = false;
	return leader;
} // WCas

#else
	#error unsupported architecture
#endif // WCas

#define unlock() fast = false

//======================================================

static TYPE PAD3 CALIGN __attribute__(( unused ));		// protect further false sharing
typedef struct CALIGN {
	VTYPE apply;
#ifdef FLAG
	VTYPE flag;
#endif // FLAG
} Flags;
static Flags * flags CALIGN;

#ifndef FLAG
static VTYPE first CALIGN;
#endif // FLAG
static TYPE PAD4 CALIGN __attribute__(( unused ));		// protect further false sharing

static void * Worker( void * arg ) {
	TYPE id = (size_t)arg;
	uint64_t entry;

	// _Atomic qualifier not preserved in typeof => VTYPE
	VTYPE * applyId = &flags[id].apply;					// optimizations
	#ifdef FLAG
	VTYPE * flagId = &flags[id].flag;
	VTYPE * flagN = &flags[N].flag;
	#endif // FLAG

	#ifdef FAST
	typeof(id) cnt = 0, oid = id;
	#endif // FAST

	NCS_DECL;

	typeof(id) thr;

	for ( int r = 0; r < RUNS; r += 1 ) {
		RTYPE randomThreadChecksum = 0;

		for ( entry = 0; stop == 0; entry += 1 ) {
			NCS;

			*applyId = true;							// entry protocol
			if ( FASTPATH( trylock( id ) ) ) {			// true => leader
				#ifndef CAS
				Fence();								// force store before more loads
				#endif // ! CAS

				#ifdef FLAG
				await( *flagId || *flagN );
				*flagN = false;
				#else
				await( first == id || first == N );
				first = id;
				#endif // FLAG
				unlock();
			} else {
				#ifdef FLAG
				await( *flagId );
				#else
				await( first == id );
				#endif // FLAG
			} // if
			#ifdef FLAG
			*flagId = false;
			#endif // FLAG

			randomThreadChecksum += CS( id );

			#ifdef CYCLEUP
			for ( thr = cycleUp( id, N ); ! flags[thr].apply; thr = cycleUp( thr, N ) );
			#else // CYCLEDOWN
			#define Mod( a, b, N ) ((a + b) < N ? (a + b) : (a + b - N))
			for ( thr = N - 1; ! flags[Mod(id, thr, N)].apply; thr -= 1 );
			#endif // CYCLEUP

			*applyId = false;							// must appear before setting first
			#ifdef CYCLEUP
			if ( FASTPATH( thr != id ) )
				#ifdef FLAG
				flags[thr].flag = true; else *flagN = true;
				#else // NOFLAG
				first = thr; else first = N;
				#endif // FLAG

			#else // CYCLEDOWN

			if ( FASTPATH( thr != 0 ) )
				#ifdef FLAG
				flags[Mod(id, thr, N)].flag = true; else *flagN = true;
				#else // NOFLAG
				first = Mod(id, thr, N); else first = N;
				#endif // FLAG
			#endif // CYCLEUP

			#ifdef FAST
			id = startpoint( cnt );						// different starting point each experiment
			cnt = cycleUp( cnt, NoStartPoints );

			applyId = &flags[id].apply;				// must reset for new id

			#ifdef FLAG
			flagId = &flags[id].flag;
			flagN = &flags[N].flag;
			#endif // FLAG
			#endif // FAST
		} // for

		Fai( sumOfThreadChecksums, randomThreadChecksum );

		#ifdef FAST
		id = oid;

		applyId = &flags[id].apply;					// must reset for new id
		#ifdef FLAG
		flagId = &flags[id].flag;
		flagN = &flags[N].flag;
		#endif // FLAG
		#endif // FAST
		entries[r][id] = entry;
		Fai( Arrived, 1 );
		while ( stop != 0 ) Pause();
		Fai( Arrived, -1 );
	} // for
	return NULL;
} // Worker

void __attribute__((noinline)) ctor() {
	flags = Allocator( (N + 1) * sizeof(typeof(flags[0])) );
	for ( typeof(N) id = 0; id <= N; id += 1 ) {		// initialize shared data
		flags[id].apply = false;
		#ifdef FLAG
		flags[id].flag = false;
		#endif // FLAG
	} // for

	#ifdef FLAG
	flags[N].flag = true;
	#else
	first = N;
	#endif // FLAG

	#ifndef CAS
	b = Allocator( N * sizeof(typeof(b[0])) );
	for ( typeof(N) id = 0; id < N; id += 1 ) {			// initialize shared data
		b[id] = false;
	} // for
	y = N;
	#endif // CAS
	unlock();
} // ctor

void __attribute__((noinline)) dtor() {
	#ifndef CAS
	free( (void *)b );
	#endif // ! CAS
	free( (void *)flags );
} // dtor

// Local Variables: //
// tab-width: 4 //
// compile-command: "gcc -Wall -Wextra -std=gnu11 -O3 -DNDEBUG -fno-reorder-functions -DPIN -DAlgorithm=ElevatorLinear -DWCasLF Harness.c -lpthread -lm -D`hostname` -DCFMT -DCNT=0" //
// End: //