OpenMP locks instead of busy-waiting with NUM_PARALLEL

Makefile.rule

@@ -90,13 +90,6 @@ VERSION = 0.3.26.dev
 # footprint penalty, even if users reduce the actual number of threads at runtime.
 # NUM_THREADS = 24
 
-# If you have enabled USE_OPENMP and your application would call
-# OpenBLAS's calculation API from multiple threads, please comment this in.
-# This flag defines how many instances of OpenBLAS's calculation API can actually
-# run in parallel. If more than NUM_PARALLEL threads call OpenBLAS's calculation API,
-# they need to wait for the preceding API calls to finish or risk data corruption.
-# NUM_PARALLEL = 2
-
 # When multithreading, OpenBLAS needs to use a memory buffer for communicating
 # and collating results for individual subranges of the original matrix. Since
 # the original GotoBLAS of the early 2000s, the default size of this buffer has

Makefile.system

@@ -304,11 +304,6 @@ HAVE_FMA3=
 include $(TOPDIR)/Makefile_kernel.conf
 endif
 
-
-ifndef NUM_PARALLEL
-NUM_PARALLEL = 1
-endif
-
 ifndef NUM_THREADS
 NUM_THREADS = $(NUM_CORES)
 endif
@@ -1476,8 +1471,6 @@ endif
 
 CCOMMON_OPT	+= -DMAX_CPU_NUMBER=$(NUM_THREADS)
 
-CCOMMON_OPT	+= -DMAX_PARALLEL_NUMBER=$(NUM_PARALLEL)
-
 ifdef USE_SIMPLE_THREADED_LEVEL3
 CCOMMON_OPT	+= -DUSE_SIMPLE_THREADED_LEVEL3
 endif

cmake/system.cmake

@@ -133,9 +133,6 @@ if (NOT CMAKE_CROSSCOMPILING)
 
 endif()
 
-if (NOT DEFINED NUM_PARALLEL)
-  set(NUM_PARALLEL 1)
-endif()
 
 if (NOT DEFINED NUM_THREADS)
   if (DEFINED NUM_CORES AND NOT NUM_CORES EQUAL 0)
@@ -475,8 +472,6 @@ endif ()
 
 set(CCOMMON_OPT "${CCOMMON_OPT} -DMAX_CPU_NUMBER=${NUM_THREADS}")
 
-set(CCOMMON_OPT "${CCOMMON_OPT} -DMAX_PARALLEL_NUMBER=${NUM_PARALLEL}")
-
 if (BUFFERSIZE)
 set(CCOMMON_OPT "${CCOMMON_OPT} -DBUFFERSIZE=${BUFFERSIZE}")
 endif ()

common.h

@@ -188,7 +188,7 @@ extern "C" {
 
 #define ALLOCA_ALIGN 63UL
 
-#define NUM_BUFFERS MAX(50,(MAX_CPU_NUMBER * 2 * MAX_PARALLEL_NUMBER))
+#define NUM_BUFFERS MAX(50,(MAX_CPU_NUMBER * 2))
 
 #ifdef NEEDBUNDERSCORE
 #define BLASFUNC(FUNC) FUNC##_

driver/level3/level3_thread.c

@@ -540,18 +540,32 @@ static int round_up(int remainder, int width, int multiple)
 	return width;
 }
 
-
 static int gemm_driver(blas_arg_t *args, BLASLONG *range_m, BLASLONG
 		       *range_n, IFLOAT *sa, IFLOAT *sb,
                        BLASLONG nthreads_m, BLASLONG nthreads_n) {
 
-#ifndef USE_OPENMP
-#ifndef OS_WINDOWS
-static pthread_mutex_t  level3_lock    = PTHREAD_MUTEX_INITIALIZER;
-#else
+#ifdef USE_OPENMP
+  static omp_lock_t level3_lock;
+  static volatile BLASLONG omp_lock_initialized = 0;
+  static BLASULONG critical_section_lock = 0;
+
+  while(omp_lock_initialized == 0)
+  {
+    blas_lock(&critical_section_lock);
+    {
+      if(omp_lock_initialized == 0)
+      {
+        omp_init_lock(&level3_lock);
+        omp_lock_initialized = 1;
+      }
+    blas_unlock(&critical_section_lock);
+    }
+  }
+#elif OS_WINDOWS
 CRITICAL_SECTION level3_lock;
 InitializeCriticalSection((PCRITICAL_SECTION)&level3_lock);
-#endif
+#else
+static pthread_mutex_t  level3_lock    = PTHREAD_MUTEX_INITIALIZER;
 #endif
 
   blas_arg_t newarg;
@@ -599,12 +613,12 @@ InitializeCriticalSection((PCRITICAL_SECTION)&level3_lock);
 #endif
 #endif
 
-#ifndef USE_OPENMP
-#ifndef OS_WINDOWS
-pthread_mutex_lock(&level3_lock);
-#else
+#ifdef USE_OPENMP
+omp_set_lock(&level3_lock);
+#elif OS_WINDOWS
 EnterCriticalSection((PCRITICAL_SECTION)&level3_lock);
-#endif
+#else
+pthread_mutex_lock(&level3_lock);
 #endif
 
 #ifdef USE_ALLOC_HEAP
@@ -732,12 +746,12 @@ EnterCriticalSection((PCRITICAL_SECTION)&level3_lock);
   free(job);
 #endif
 
-#ifndef USE_OPENMP
-#ifndef OS_WINDOWS
-  pthread_mutex_unlock(&level3_lock);
-#else
+#ifdef USE_OPENMP
+  omp_unset_lock(&level3_lock);
+#elif OS_WINDOWS
   LeaveCriticalSection((PCRITICAL_SECTION)&level3_lock);
-#endif
+#else
+  pthread_mutex_unlock(&level3_lock);
 #endif
 
   return 0;

driver/others/blas_server_omp.c

@@ -73,31 +73,27 @@ int blas_omp_threads_local = 1;
 
 extern int openblas_omp_adaptive_env(void);
 
-static void * blas_thread_buffer[MAX_PARALLEL_NUMBER][MAX_CPU_NUMBER];
-#ifdef HAVE_C11
-static atomic_bool blas_buffer_inuse[MAX_PARALLEL_NUMBER];
-#else
-static _Bool blas_buffer_inuse[MAX_PARALLEL_NUMBER];
-#endif
+static void * blas_thread_buffer[MAX_CPU_NUMBER];
 
 static void adjust_thread_buffers(void) {
 
-  int i=0, j=0;
+  int i=0;
+
+  // Add assertion to ensure blas_cpu_number is within valid range
+  assert(0 <= blas_cpu_number && blas_cpu_number <= MAX_CPU_NUMBER);
 
   //adjust buffer for each thread
-  for(i=0; i < MAX_PARALLEL_NUMBER; i++) {
-    for(j=0; j < blas_cpu_number; j++){
-      if(blas_thread_buffer[i][j] == NULL){
-        blas_thread_buffer[i][j] = blas_memory_alloc(2);
+    for(i=0; i < blas_cpu_number; i++){
+      if(blas_thread_buffer[i] == NULL){
+        blas_thread_buffer[i] = blas_memory_alloc(2);
       }
     }
-    for(; j < MAX_CPU_NUMBER; j++){
-      if(blas_thread_buffer[i][j] != NULL){
-        blas_memory_free(blas_thread_buffer[i][j]);
-        blas_thread_buffer[i][j] = NULL;
+    for(; i < MAX_CPU_NUMBER; i++){
+      if(blas_thread_buffer[i] != NULL){
+        blas_memory_free(blas_thread_buffer[i]);
+        blas_thread_buffer[i] = NULL;
       }
     }
-  }
 }
 
 void goto_set_num_threads(int num_threads) {
@@ -147,17 +143,15 @@ extern int openblas_omp_num_threads_env(void);
 }
 
 int BLASFUNC(blas_thread_shutdown)(void){
-  int i=0, j=0;
+  int i=0;
   blas_server_avail = 0;
 
-  for(i=0; i<MAX_PARALLEL_NUMBER; i++) {
-    for(j=0; j<MAX_CPU_NUMBER; j++){
-      if(blas_thread_buffer[i][j]!=NULL){
-        blas_memory_free(blas_thread_buffer[i][j]);
-        blas_thread_buffer[i][j]=NULL;
+    for(i=0; i<MAX_CPU_NUMBER; i++){
+      if(blas_thread_buffer[i]!=NULL){
+        blas_memory_free(blas_thread_buffer[i]);
+        blas_thread_buffer[i]=NULL;
       }
     }
-  }
 
   return 0;
 }
@@ -285,7 +279,7 @@ static void legacy_exec(void *func, int mode, blas_arg_t *args, void *sb){
    }
 }
 
-static void exec_threads(blas_queue_t *queue, int buf_index){
+static void exec_threads(blas_queue_t *queue){
 
   void *buffer, *sa, *sb;
   int pos=0, release_flag=0;
@@ -306,7 +300,7 @@ static void exec_threads(blas_queue_t *queue, int buf_index){
   if ((sa == NULL) && (sb == NULL) && ((queue -> mode & BLAS_PTHREAD) == 0)) {
 
     pos = omp_get_thread_num();
-    buffer = blas_thread_buffer[buf_index][pos];
+    buffer = blas_thread_buffer[pos];
 
     //fallback
     if(buffer==NULL) {
@@ -392,7 +386,7 @@ int exec_blas(BLASLONG num, blas_queue_t *queue){
   // Handle lazy re-init of the thread-pool after a POSIX fork
   if (unlikely(blas_server_avail == 0)) blas_thread_init();
 
-  BLASLONG i, buf_index;
+  BLASLONG i;
 
   if ((num <= 0) || (queue == NULL)) return 0;
 
@@ -407,23 +401,6 @@ int exec_blas(BLASLONG num, blas_queue_t *queue){
   }
 #endif
 
-  while(true) {
-    for(i=0; i < MAX_PARALLEL_NUMBER; i++) {
-#ifdef HAVE_C11
-      _Bool inuse = false;
-      if(atomic_compare_exchange_weak(&blas_buffer_inuse[i], &inuse, true)) {
-#else
-      if(blas_buffer_inuse[i] == false) {
-        blas_buffer_inuse[i] = true;
-#endif
-        buf_index = i;
-        break;
-      }
-    }
-    if(i != MAX_PARALLEL_NUMBER)
-      break;
-  }
-
 if (openblas_omp_adaptive_env() != 0) {
 #pragma omp parallel for num_threads(num) schedule(OMP_SCHED)
   for (i = 0; i < num; i ++) {
@@ -432,7 +409,7 @@ if (openblas_omp_adaptive_env() != 0) {
     queue[i].position = i;
 #endif
 
-    exec_threads(&queue[i], buf_index);
+    exec_threads(&queue[i]);
   }
 } else {
 #pragma omp parallel for schedule(OMP_SCHED)
@@ -442,16 +419,9 @@ if (openblas_omp_adaptive_env() != 0) {
     queue[i].position = i;
 #endif
 
-    exec_threads(&queue[i], buf_index);
+    exec_threads(&queue[i]);
   }
 }
-
-#ifdef HAVE_C11
-  atomic_store(&blas_buffer_inuse[buf_index], false);
-#else
-  blas_buffer_inuse[buf_index] = false;
-#endif
-
   return 0;
 }