Reducing threads for multi-threaded GEMMs on small matrices.

Author: Tim Moon

driver/level3/level3_thread.c

@@ -684,8 +684,6 @@ int CNAME(blas_arg_t *args, BLASLONG *range_m, BLASLONG *range_n, FLOAT *sa, FLO
   BLASLONG m = args -> m;
   BLASLONG n = args -> n;
   BLASLONG nthreads = args -> nthreads;
-  BLASLONG divN, divT;
-  int mode;
 
   if (nthreads  == 1) {
     GEMM_LOCAL(args, range_m, range_n, sa, sb, 0);
@@ -706,66 +704,21 @@ int CNAME(blas_arg_t *args, BLASLONG *range_m, BLASLONG *range_n, FLOAT *sa, FLO
     n = n_to - n_from;
   }
 
-  if ((m < nthreads * SWITCH_RATIO) || (n < nthreads * SWITCH_RATIO)) {
+  if ((m < 2 * SWITCH_RATIO) || (n < 2 * SWITCH_RATIO)) {
     GEMM_LOCAL(args, range_m, range_n, sa, sb, 0);
     return 0;
   }
 
-  divT = nthreads;
-  divN = 1;
-
-#if 0
-  while ((GEMM_P * divT > m * SWITCH_RATIO) && (divT > 1)) {
-    do {
-      divT --;
-      divN = 1;
-      while (divT * divN < nthreads) divN ++;
-    } while ((divT * divN != nthreads) && (divT > 1));
+  if (m < nthreads * SWITCH_RATIO) {
+    nthreads = blas_quickdivide(m, SWITCH_RATIO);
   }
-#endif
-
-  // fprintf(stderr, "divN = %4ld  divT = %4ld\n", divN, divT);
-
-  args -> nthreads = divT;
-
-  if (divN == 1){
-
-    gemm_driver(args, range_m, range_n, sa, sb, 0);
-  } else {
-#ifndef COMPLEX
-#ifdef XDOUBLE
-    mode  =  BLAS_XDOUBLE | BLAS_REAL;
-#elif defined(DOUBLE)
-    mode  =  BLAS_DOUBLE  | BLAS_REAL;
-#else
-    mode  =  BLAS_SINGLE  | BLAS_REAL;
-#endif
-#else
-#ifdef XDOUBLE
-    mode  =  BLAS_XDOUBLE | BLAS_COMPLEX;
-#elif defined(DOUBLE)
-    mode  =  BLAS_DOUBLE  | BLAS_COMPLEX;
-#else
-    mode  =  BLAS_SINGLE  | BLAS_COMPLEX;
-#endif
-#endif
-
-#if defined(TN) || defined(TT) || defined(TR) || defined(TC) || \
-    defined(CN) || defined(CT) || defined(CR) || defined(CC)
-    mode |= (BLAS_TRANSA_T);
-#endif
-#if defined(NT) || defined(TT) || defined(RT) || defined(CT) || \
-    defined(NC) || defined(TC) || defined(RC) || defined(CC)
-    mode |= (BLAS_TRANSB_T);
-#endif
-
-#ifdef OS_WINDOWS
-    gemm_thread_n(mode, args, range_m, range_n, GEMM_LOCAL,  sa, sb, divN);
-#else
-    gemm_thread_n(mode, args, range_m, range_n, gemm_driver, sa, sb, divN);
-#endif
-
+  if (n < nthreads * SWITCH_RATIO) {
+    nthreads = blas_quickdivide(n, SWITCH_RATIO);
   }
 
+  args -> nthreads = nthreads;
+  
+  gemm_driver(args, range_m, range_n, sa, sb, 0);
+
   return 0;
 }