static void allocate_memory(void) {
int64_t maxlocalverts = g.max_nlocalverts;
int lg_local_queue_size = lg_int64_t((maxlocalverts + ulong_bits_squared - 1) / ulong_bits_squared * ulong_bits_squared);
g_lg_local_queue_size = lg_local_queue_size;
int64_t local_queue_summary_size = (INT64_C(1) << lg_local_queue_size) / ulong_bits_squared;
int64_t local_queue_size = local_queue_summary_size * ulong_bits;
g_local_queue_summary_size = local_queue_summary_size;
g_local_queue_size = local_queue_size;
int64_t global_queue_summary_size = MUL_SIZE(local_queue_summary_size);
int64_t global_queue_size = MUL_SIZE(local_queue_size);
g_global_queue_summary_size = global_queue_summary_size;
g_global_queue_size = global_queue_size;
g_in_queue = (unsigned long*)xmalloc(global_queue_size * sizeof(unsigned long));
g_in_queue_summary = (unsigned long*)xmalloc(global_queue_summary_size * sizeof(unsigned long));
g_out_queue = (unsigned long*)xmalloc(local_queue_size * sizeof(unsigned long));
g_out_queue_summary = (unsigned long*)xmalloc(local_queue_summary_size * sizeof(unsigned long));
g_visited = (unsigned long*)xmalloc(local_queue_size * sizeof(unsigned long));
}
/* This version is the traditional level-synchronized BFS using two queues. A
* bitmap is used to indicate which vertices have been visited. Messages are
* sent and processed asynchronously throughout the code to hopefully overlap
* communication with computation. */
void run_bfs(int64_t root, int64_t* pred) {
allocate_memory();
const ptrdiff_t nlocalverts = g.nlocalverts;
const size_t* const restrict rowstarts = g.rowstarts;
const int64_t* const restrict column = g.column;
int64_t maxlocalverts = g.max_nlocalverts;
/* Set up the visited bitmap. */
const int ulong_bits = sizeof(unsigned long) * CHAR_BIT;
const int ulong_bits_squared = ulong_bits * ulong_bits;
int64_t local_queue_summary_size = (maxlocalverts + ulong_bits_squared - 1) / ulong_bits_squared;
int64_t local_queue_size = local_queue_summary_size * ulong_bits;
int lg_local_queue_size = lg_int64_t(local_queue_size);
int64_t global_queue_summary_size = MUL_SIZE(local_queue_summary_size);
int64_t global_queue_size = MUL_SIZE(local_queue_size);
#define SWIZZLE_VERTEX(c) ((VERTEX_OWNER(c) << lg_local_queue_size) * ulong_bits | VERTEX_LOCAL(c))
#if 0
int64_t* restrict column_swizzled = (int64_t*)xmalloc(nlocaledges * sizeof(int64_t));
{
size_t i;
for (i = 0; i < nlocaledges; ++i) {
int64_t c = column[i];
column_swizzled[i] = SWIZZLE_VERTEX(c);
}
}
#endif
unsigned long* restrict in_queue = g_in_queue;
memset(in_queue, 0, global_queue_size * sizeof(unsigned long));
unsigned long* restrict in_queue_summary = g_in_queue_summary;
memset(in_queue_summary, 0, global_queue_summary_size * sizeof(unsigned long));
unsigned long* restrict out_queue = g_out_queue;
unsigned long* restrict out_queue_summary = g_out_queue_summary;
unsigned long* restrict visited = g_visited;
memset(visited, 0, local_queue_size * sizeof(unsigned long));
#define SET_IN(v) do {int64_t vs = SWIZZLE_VERTEX(v); size_t word_idx = vs / ulong_bits; int bit_idx = vs % ulong_bits; unsigned long mask = (1UL << bit_idx); in_queue_summary[word_idx / ulong_bits] |= (1UL << (word_idx % ulong_bits)); in_queue[word_idx] |= mask;} while (0)
#define TEST_IN(vs) (((in_queue_summary[vs / ulong_bits / ulong_bits] & (1UL << ((vs / ulong_bits) % ulong_bits))) != 0) && ((in_queue[vs / ulong_bits] & (1UL << (vs % ulong_bits))) != 0))
#define TEST_VISITED_LOCAL(v) ((visited[(v) / ulong_bits] & (1UL << ((v) % ulong_bits))) != 0)
// #define SET_VISITED_LOCAL(v) do {size_t word_idx = (v) / ulong_bits; int bit_idx = (v) % ulong_bits; unsigned long mask = (1UL << bit_idx); __sync_fetch_and_or(&visited[word_idx], mask); __sync_fetch_and_or(&out_queue[word_idx], mask);} while (0)
#define SET_VISITED_LOCAL(v) do {size_t word_idx = (v) / ulong_bits; int bit_idx = (v) % ulong_bits; unsigned long mask = (1UL << bit_idx); visited[word_idx] |= mask; out_queue[word_idx] |= mask;} while (0)
SET_IN(root);
{ptrdiff_t i; _Pragma("omp parallel for schedule(static)") for (i = 0; i < nlocalverts; ++i) pred[i] = -1;}
if (VERTEX_OWNER(root) == rank) {
pred[VERTEX_LOCAL(root)] = root;
SET_VISITED_LOCAL(VERTEX_LOCAL(root));
}
uint16_t cur_level = 0;
while (1) {
++cur_level;
#if 0
if (rank == 0) fprintf(stderr, "BFS level %" PRIu16 "\n", cur_level);
#endif
memset(out_queue, 0, local_queue_size * sizeof(unsigned long));
// memset(out_queue_summary, 0, local_queue_summary_size * sizeof(unsigned long));
ptrdiff_t i, ii;
#if 0
#pragma omp parallel for schedule(static)
for (i = 0; i < global_queue_summary_size; ++i) {
unsigned long val = 0UL;
int j;
unsigned long mask = 1UL;
for (j = 0; j < ulong_bits; ++j, mask <<= 1) {
if (in_queue[i * ulong_bits + j]) val |= mask;
}
in_queue_summary[i] = val;
}
#endif
unsigned long not_done = 0;
#pragma omp parallel for schedule(static) reduction(|:not_done)
for (ii = 0; ii < nlocalverts; ii += ulong_bits) {
size_t i, i_end = ii + ulong_bits;
if (i_end > nlocalverts) i_end = nlocalverts;
for (i = ii; i < i_end; ++i) {
if (!TEST_VISITED_LOCAL(i)) {
size_t j, j_end = rowstarts[i + 1];
for (j = rowstarts[i]; j < j_end; ++j) {
int64_t v1 = column[j];
int64_t v1_swizzled = SWIZZLE_VERTEX(v1);
if (TEST_IN(v1_swizzled)) {
pred[i] = (v1 & INT64_C(0xFFFFFFFFFFFF)) | ((int64_t)cur_level << 48);
not_done |= 1;
SET_VISITED_LOCAL(i);
break;
}
}
}
}
}
#if 1
#pragma omp parallel for schedule(static)
for (i = 0; i < local_queue_summary_size; ++i) {
unsigned long val = 0UL;
int j;
unsigned long mask = 1UL;
for (j = 0; j < ulong_bits; ++j, mask <<= 1) {
unsigned long full_val = out_queue[i * ulong_bits + j];
visited[i * ulong_bits + j] |= full_val;
if (full_val) val |= mask;
}
out_queue_summary[i] = val;
// not_done |= val;
}
#endif
MPI_Allreduce(MPI_IN_PLACE, ¬_done, 1, MPI_UNSIGNED_LONG, MPI_BOR, MPI_COMM_WORLD);
if (not_done == 0) break;
MPI_Allgather(out_queue, local_queue_size, MPI_UNSIGNED_LONG, in_queue, local_queue_size, MPI_UNSIGNED_LONG, MPI_COMM_WORLD);
MPI_Allgather(out_queue_summary, local_queue_summary_size, MPI_UNSIGNED_LONG, in_queue_summary, local_queue_summary_size, MPI_UNSIGNED_LONG, MPI_COMM_WORLD);
}
deallocate_memory();
}