Commit db0d63ea authored by Pedro Gonnet's avatar Pedro Gonnet
Browse files

do away with OpenMP critical sections altogether.


Former-commit-id: 552857a49f282722571984e84aa3843ecd248e92
parent 3d9ebb0c
......@@ -23,3 +23,4 @@
#define atomic_add(v,i) __sync_fetch_and_add( v , i )
#define atomic_inc(v) atomic_add( v , 1 )
#define atomic_dec(v) atomic_add( v , -1 )
#define atomic_cas(v,o,n) __sync_val_compare_and_swap( v , o , n )
......@@ -339,9 +339,9 @@ void space_rebuild ( struct space *s , double cell_max ) {
void parts_sort ( struct part *parts , int *ind , int N , int min , int max ) {
struct {
int i, j, min, max;
int i, j, min, max, ready;
} qstack[space_qstack];
int first, last, waiting;
volatile int first, last, waiting;
int pivot;
int i, ii, j, jj, temp_i, qid;
......@@ -352,7 +352,10 @@ void parts_sort ( struct part *parts , int *ind , int N , int min , int max ) {
qstack[0].j = N-1;
qstack[0].min = min;
qstack[0].max = max;
first = 0; last = 0; waiting = 1;
qstack[0].ready = 1;
for ( i = 1 ; i < space_qstack ; i++ )
qstack[i].ready = 0;
first = 0; last = 1; waiting = 1;
/* Parallel bit. */
#pragma omp parallel default(shared) private(pivot,i,ii,j,jj,min,max,temp_i,qid,temp_p)
......@@ -361,26 +364,17 @@ void parts_sort ( struct part *parts , int *ind , int N , int min , int max ) {
/* Main loop. */
while ( waiting > 0 ) {
/* Try to get an index off the stack. */
qid = -1;
while ( waiting > 0 && qid < 0 ) {
#pragma omp critical (stack)
{
if ( last - first > space_qstack )
error( "Sorting stack overflow." );
if ( first <= last ) {
qid = first;
first += 1;
}
}
}
/* Grab an interval off the queue. */
qid = atomic_inc( &first ) % space_qstack;
/* Did we get an index? */
if ( qid < 0 )
continue;
/* Wait for the interval to be ready. */
while ( waiting > 0 && atomic_cas( &qstack[qid].ready , 1 , 0 ) != 1 );
/* Broke loop for all the wrong reasons? */
if ( waiting == 0 )
break;
/* Get the stack entry. */
qid %= space_qstack;
i = qstack[qid].i;
j = qstack[qid].j;
min = qstack[qid].min;
......@@ -415,43 +409,36 @@ void parts_sort ( struct part *parts , int *ind , int N , int min , int max ) {
/* Recurse on the left? */
if ( jj > i && pivot > min ) {
#pragma omp critical (stack)
{
last += 1;
qid = last % space_qstack;
qstack[qid].i = i;
qstack[qid].j = jj;
qstack[qid].min = min;
qstack[qid].max = pivot;
waiting += 1;
}
qid = atomic_inc( &last ) % space_qstack;
qstack[qid].i = i;
qstack[qid].j = jj;
qstack[qid].min = min;
qstack[qid].max = pivot;
qstack[qid].ready = 1;
atomic_inc( &waiting );
}
/* Recurse on the right? */
if ( jj+1 < j && pivot+1 < max ) {
#pragma omp critical (stack)
{
last += 1;
qid = last % space_qstack;
qstack[qid].i = jj+1;
qstack[qid].j = j;
qstack[qid].min = pivot+1;
qstack[qid].max = max;
waiting += 1;
}
qid = atomic_inc( &last ) % space_qstack;
qstack[qid].i = jj+1;
qstack[qid].j = j;
qstack[qid].min = pivot+1;
qstack[qid].max = max;
qstack[qid].ready = 1;
atomic_inc( &waiting );
}
#pragma omp critical (stack)
waiting -= 1;
atomic_dec( &waiting );
} /* main loop. */
} /* parallel bit. */
/* Verify sort. */
/* for ( i = 1 ; i < N ; i++ )
for ( i = 1 ; i < N ; i++ )
if ( ind[i-1] > ind[i] )
error( "Sorting failed!" ); */
error( "Sorting failed!" );
}
......
......@@ -98,7 +98,6 @@ struct space {
/* function prototypes. */
void parts_sort ( struct part *parts , int *ind , int N , int min , int max );
void parts_sort_par ( struct part *parts , int *ind , int N , int min , int max );
struct cell *space_getcell ( struct space *s );
int space_getsid ( struct space *s , struct cell **ci , struct cell **cj , double *shift );
void space_init ( struct space *s , double dim[3] , struct part *parts , int N , int periodic , double h_max );
......
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