OpenBLAS/driver/level3/level3_thread.c

/*********************************************************************/
/* Copyright 2009, 2010 The University of Texas at Austin.           */
/* All rights reserved.                                              */
/*                                                                   */
/* Redistribution and use in source and binary forms, with or        */
/* without modification, are permitted provided that the following   */
/* conditions are met:                                               */
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/*   1. Redistributions of source code must retain the above         */
/*      copyright notice, this list of conditions and the following  */
/*      disclaimer.                                                  */
/*                                                                   */
/*   2. Redistributions in binary form must reproduce the above      */
/*      copyright notice, this list of conditions and the following  */
/*      disclaimer in the documentation and/or other materials       */
/*      provided with the distribution.                              */
/*                                                                   */
/*    THIS  SOFTWARE IS PROVIDED  BY THE  UNIVERSITY OF  TEXAS AT    */
/*    AUSTIN  ``AS IS''  AND ANY  EXPRESS OR  IMPLIED WARRANTIES,    */
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/*********************************************************************/

#ifndef CACHE_LINE_SIZE
#define CACHE_LINE_SIZE 8
#endif

#ifndef DIVIDE_RATE
#define DIVIDE_RATE 2
#endif

#ifndef SWITCH_RATIO
#define SWITCH_RATIO 2
#endif

#ifndef GEMM_LOCAL
#if   defined(NN)
#define GEMM_LOCAL    GEMM_NN
#elif defined(NT)
#define GEMM_LOCAL    GEMM_NT
#elif defined(NR)
#define GEMM_LOCAL    GEMM_NR
#elif defined(NC)
#define GEMM_LOCAL    GEMM_NC
#elif defined(TN)
#define GEMM_LOCAL    GEMM_TN
#elif defined(TT)
#define GEMM_LOCAL    GEMM_TT
#elif defined(TR)
#define GEMM_LOCAL    GEMM_TR
#elif defined(TC)
#define GEMM_LOCAL    GEMM_TC
#elif defined(RN)
#define GEMM_LOCAL    GEMM_RN
#elif defined(RT)
#define GEMM_LOCAL    GEMM_RT
#elif defined(RR)
#define GEMM_LOCAL    GEMM_RR
#elif defined(RC)
#define GEMM_LOCAL    GEMM_RC
#elif defined(CN)
#define GEMM_LOCAL    GEMM_CN
#elif defined(CT)
#define GEMM_LOCAL    GEMM_CT
#elif defined(CR)
#define GEMM_LOCAL    GEMM_CR
#elif defined(CC)
#define GEMM_LOCAL    GEMM_CC
#endif
#endif

typedef struct {
  volatile BLASLONG working[MAX_CPU_NUMBER][CACHE_LINE_SIZE * DIVIDE_RATE];
} job_t;


#ifndef BETA_OPERATION
#ifndef COMPLEX
#define BETA_OPERATION(M_FROM, M_TO, N_FROM, N_TO, BETA, C, LDC) \
	GEMM_BETA((M_TO) - (M_FROM), (N_TO - N_FROM), 0, \
		  BETA[0], NULL, 0, NULL, 0, \
		  (FLOAT *)(C) + ((M_FROM) + (N_FROM) * (LDC)) * COMPSIZE, LDC)
#else
#define BETA_OPERATION(M_FROM, M_TO, N_FROM, N_TO, BETA, C, LDC) \
	GEMM_BETA((M_TO) - (M_FROM), (N_TO - N_FROM), 0, \
		  BETA[0], BETA[1], NULL, 0, NULL, 0, \
		  (FLOAT *)(C) + ((M_FROM) + (N_FROM) * (LDC)) * COMPSIZE, LDC)
#endif
#endif

#ifndef ICOPY_OPERATION
#if defined(NN) || defined(NT) || defined(NC) || defined(NR) || \
    defined(RN) || defined(RT) || defined(RC) || defined(RR)
#define ICOPY_OPERATION(M, N, A, LDA, X, Y, BUFFER) GEMM_ITCOPY(M, N, (FLOAT *)(A) + ((Y) + (X) * (LDA)) * COMPSIZE, LDA, BUFFER);
#else
#define ICOPY_OPERATION(M, N, A, LDA, X, Y, BUFFER) GEMM_INCOPY(M, N, (FLOAT *)(A) + ((X) + (Y) * (LDA)) * COMPSIZE, LDA, BUFFER);
#endif
#endif

#ifndef OCOPY_OPERATION
#if defined(NN) || defined(TN) || defined(CN) || defined(RN) || \
    defined(NR) || defined(TR) || defined(CR) || defined(RR)
#define OCOPY_OPERATION(M, N, A, LDA, X, Y, BUFFER) GEMM_ONCOPY(M, N, (FLOAT *)(A) + ((X) + (Y) * (LDA)) * COMPSIZE, LDA, BUFFER);
#else
#define OCOPY_OPERATION(M, N, A, LDA, X, Y, BUFFER) GEMM_OTCOPY(M, N, (FLOAT *)(A) + ((Y) + (X) * (LDA)) * COMPSIZE, LDA, BUFFER);
#endif
#endif

#ifndef KERNEL_FUNC
#if defined(NN) || defined(NT) || defined(TN) || defined(TT)
#define KERNEL_FUNC	GEMM_KERNEL_N
#endif
#if defined(CN) || defined(CT) || defined(RN) || defined(RT)
#define KERNEL_FUNC	GEMM_KERNEL_L
#endif
#if defined(NC) || defined(TC) || defined(NR) || defined(TR)
#define KERNEL_FUNC	GEMM_KERNEL_R
#endif
#if defined(CC) || defined(CR) || defined(RC) || defined(RR)
#define KERNEL_FUNC	GEMM_KERNEL_B
#endif
#endif

#ifndef KERNEL_OPERATION
#ifndef COMPLEX
#define KERNEL_OPERATION(M, N, K, ALPHA, SA, SB, C, LDC, X, Y) \
	KERNEL_FUNC(M, N, K, ALPHA[0], SA, SB, (FLOAT *)(C) + ((X) + (Y) * LDC) * COMPSIZE, LDC)
#else
#define KERNEL_OPERATION(M, N, K, ALPHA, SA, SB, C, LDC, X, Y) \
	KERNEL_FUNC(M, N, K, ALPHA[0], ALPHA[1], SA, SB, (FLOAT *)(C) + ((X) + (Y) * LDC) * COMPSIZE, LDC)
#endif
#endif

#ifndef FUSED_KERNEL_OPERATION
#if defined(NN) || defined(TN) || defined(CN) || defined(RN) || \
    defined(NR) || defined(TR) || defined(CR) || defined(RR)
#ifndef COMPLEX
#define FUSED_KERNEL_OPERATION(M, N, K, ALPHA, SA, SB, B, LDB, C, LDC, I, J, L) \
	FUSED_GEMM_KERNEL_N(M, N, K, ALPHA[0], SA, SB, \
	(FLOAT *)(B) + ((L) + (J) * LDB) * COMPSIZE, LDB, (FLOAT *)(C) + ((I) + (J) * LDC) * COMPSIZE, LDC)
#else
#define FUSED_KERNEL_OPERATION(M, N, K, ALPHA, SA, SB, B, LDB, C, LDC, I, J, L) \
	FUSED_GEMM_KERNEL_N(M, N, K, ALPHA[0], ALPHA[1], SA, SB, \
	(FLOAT *)(B) + ((L) + (J) * LDB) * COMPSIZE, LDB, (FLOAT *)(C) + ((I) + (J) * LDC) * COMPSIZE, LDC)

#endif
#else
#ifndef COMPLEX
#define FUSED_KERNEL_OPERATION(M, N, K, ALPHA, SA, SB, B, LDB, C, LDC, I, J, L) \
	FUSED_GEMM_KERNEL_T(M, N, K, ALPHA[0], SA, SB, \
	(FLOAT *)(B) + ((J) + (L) * LDB) * COMPSIZE, LDB, (FLOAT *)(C) + ((I) + (J) * LDC) * COMPSIZE, LDC)
#else
#define FUSED_KERNEL_OPERATION(M, N, K, ALPHA, SA, SB, B, LDB, C, LDC, I, J, L) \
	FUSED_GEMM_KERNEL_T(M, N, K, ALPHA[0], ALPHA[1], SA, SB, \
	(FLOAT *)(B) + ((J) + (L) * LDB) * COMPSIZE, LDB, (FLOAT *)(C) + ((I) + (J) * LDC) * COMPSIZE, LDC)
#endif
#endif
#endif

#ifndef A
#define A	args -> a
#endif
#ifndef LDA
#define LDA	args -> lda
#endif
#ifndef B
#define B	args -> b
#endif
#ifndef LDB
#define LDB	args -> ldb
#endif
#ifndef C
#define C	args -> c
#endif
#ifndef LDC
#define LDC	args -> ldc
#endif
#ifndef M
#define M	args -> m
#endif
#ifndef N
#define N	args -> n
#endif
#ifndef K
#define K	args -> k
#endif

#ifdef TIMING
#define START_RPCC()		rpcc_counter = rpcc()
#define STOP_RPCC(COUNTER)	COUNTER  += rpcc() - rpcc_counter
#else
#define START_RPCC()
#define STOP_RPCC(COUNTER)
#endif

static int inner_thread(blas_arg_t *args, BLASLONG *range_m, BLASLONG *range_n, FLOAT *sa, FLOAT *sb, BLASLONG mypos){

  FLOAT *buffer[DIVIDE_RATE];

  BLASLONG k, lda, ldb, ldc;
  BLASLONG m_from, m_to, n_from, n_to, N_from, N_to;

  FLOAT *alpha, *beta;
  FLOAT *a, *b, *c;
  job_t *job = (job_t *)args -> common;
  BLASLONG xxx, bufferside;

  BLASLONG ls, min_l, jjs, min_jj;
  BLASLONG is, min_i, div_n;

  BLASLONG i, current;
  BLASLONG l1stride, l2size;

#ifdef TIMING
  BLASULONG rpcc_counter;
  BLASULONG copy_A = 0;
  BLASULONG copy_B = 0;
  BLASULONG kernel = 0;
  BLASULONG waiting1 = 0;
  BLASULONG waiting2 = 0;
  BLASULONG waiting3 = 0;
  BLASULONG waiting6[MAX_CPU_NUMBER];
  BLASULONG ops    = 0;

  for (i = 0; i < args -> nthreads; i++) waiting6[i] = 0;
#endif

  k = K;

  a = (FLOAT *)A;
  b = (FLOAT *)B;
  c = (FLOAT *)C;

  lda = LDA;
  ldb = LDB;
  ldc = LDC;

  alpha = (FLOAT *)args -> alpha;
  beta  = (FLOAT *)args -> beta;

  m_from = 0;
  m_to   = M;

  if (range_m) {
    m_from = range_m[0];
    m_to   = range_m[1];
  }

  n_from = 0;
  n_to   = N;

  N_from = 0;
  N_to   = N;

  if (range_n) {
    n_from = range_n[mypos + 0];
    n_to   = range_n[mypos + 1];

    N_from = range_n[0];
    N_to   = range_n[args -> nthreads];
  }

  if (beta) {
#ifndef COMPLEX
    if (beta[0] != ONE)
#else
    if ((beta[0] != ONE) || (beta[1] != ZERO))
#endif
      BETA_OPERATION(m_from, m_to, N_from, N_to, beta, c, ldc);
  }

  if ((k == 0) || (alpha == NULL)) return 0;

  if ((alpha[0] == ZERO)
#ifdef COMPLEX
      && (alpha[1] == ZERO)
#endif
      ) return 0;

  l2size = GEMM_P * GEMM_Q;

#if 0
  fprintf(stderr, "Thread[%ld]  m_from : %ld m_to : %ld n_from : %ld n_to : %ld N_from : %ld N_to : %ld\n",
	  mypos, m_from, m_to, n_from, n_to, N_from, N_to);

  fprintf(stderr, "GEMM: P = %4ld  Q = %4ld  R = %4ld\n", (BLASLONG)GEMM_P, (BLASLONG)GEMM_Q, (BLASLONG)GEMM_R);

#endif

  div_n = (n_to - n_from + DIVIDE_RATE - 1) / DIVIDE_RATE;
  
  buffer[0] = sb;
  for (i = 1; i < DIVIDE_RATE; i++) {
    buffer[i] = buffer[i - 1] + GEMM_Q * ((div_n + GEMM_UNROLL_N - 1) & ~(GEMM_UNROLL_N - 1)) * COMPSIZE;
  }
  

  for(ls = 0; ls < k; ls += min_l){

    min_l = k - ls;

    if (min_l >= GEMM_Q * 2) {
      min_l  = GEMM_Q;
    } else {
      if (min_l > GEMM_Q) min_l = (min_l + 1) / 2;
    }

    l1stride = 1;
    min_i = m_to - m_from;
    
    if (min_i >= GEMM_P * 2) {
      min_i = GEMM_P;
    } else {
      if (min_i > GEMM_P) {
	min_i = (min_i / 2 + GEMM_UNROLL_M - 1) & ~(GEMM_UNROLL_M - 1);
      } else {
	if (args -> nthreads == 1) l1stride = 0;
      }
    }

    START_RPCC();
    
    ICOPY_OPERATION(min_l, min_i, a, lda, ls, m_from, sa);
    
    STOP_RPCC(copy_A);
    
    div_n = (n_to - n_from + DIVIDE_RATE - 1) / DIVIDE_RATE;
    
    for (xxx = n_from, bufferside = 0; xxx < n_to; xxx += div_n, bufferside ++) {
      
      START_RPCC();
      
      /* Make sure if no one is using buffer */
      for (i = 0; i < args -> nthreads; i++)
	while (job[mypos].working[i][CACHE_LINE_SIZE * bufferside]) {YIELDING;};
      
      STOP_RPCC(waiting1);
      
#if defined(FUSED_GEMM) && !defined(TIMING)

      FUSED_KERNEL_OPERATION(min_i, MIN(n_to, xxx + div_n) - xxx, min_l, alpha,
			     sa, buffer[bufferside], b, ldb, c, ldc, m_from, xxx, ls);

#else

      for(jjs = xxx; jjs < MIN(n_to, xxx + div_n); jjs += min_jj){
	min_jj = MIN(n_to, xxx + div_n) - jjs;

#if defined(BULLDOZER) && defined(ARCH_X86_64) && defined(DOUBLE) && !defined(COMPLEX)
	if (min_jj >= 12*GEMM_UNROLL_N) min_jj = 12*GEMM_UNROLL_N;
	else
		if (min_jj >= 6*GEMM_UNROLL_N) min_jj = 6*GEMM_UNROLL_N;
		else
			if (min_jj >= 3*GEMM_UNROLL_N) min_jj = 3*GEMM_UNROLL_N;
			else
				if (min_jj > GEMM_UNROLL_N) min_jj = GEMM_UNROLL_N;
#else

	if (min_jj > GEMM_UNROLL_N) min_jj = GEMM_UNROLL_N;
#endif	

	START_RPCC();
	
	OCOPY_OPERATION(min_l, min_jj, b, ldb, ls, jjs, 
			buffer[bufferside] + min_l * (jjs - xxx) * COMPSIZE * l1stride);
	
	STOP_RPCC(copy_B);
	
	START_RPCC();
	
	KERNEL_OPERATION(min_i, min_jj, min_l, alpha,
			 sa, buffer[bufferside] + min_l * (jjs - xxx) * COMPSIZE * l1stride,
			 c, ldc, m_from, jjs);
	  
	STOP_RPCC(kernel);

#ifdef TIMING
	  ops += 2 * min_i * min_jj * min_l;
#endif

      }
#endif
	
      for (i = 0; i < args -> nthreads; i++) job[mypos].working[i][CACHE_LINE_SIZE * bufferside] = (BLASLONG)buffer[bufferside];
      WMB;
    }

    current = mypos;
    
    do {
      current ++;
      if (current >= args -> nthreads) current = 0;
      
      div_n = (range_n[current + 1]  - range_n[current] + DIVIDE_RATE - 1) / DIVIDE_RATE;
      
      for (xxx = range_n[current], bufferside = 0; xxx < range_n[current + 1]; xxx += div_n, bufferside ++) {
	
	if (current != mypos) {
	  
	  START_RPCC();
	  
	  /* thread has to wait */
	  while(job[current].working[mypos][CACHE_LINE_SIZE * bufferside] == 0) {YIELDING;};
	  
	  STOP_RPCC(waiting2);
	    
	  START_RPCC();

	  KERNEL_OPERATION(min_i, MIN(range_n[current + 1]  - xxx,  div_n), min_l, alpha,
			   sa, (FLOAT *)job[current].working[mypos][CACHE_LINE_SIZE * bufferside],
			   c, ldc, m_from, xxx);

	STOP_RPCC(kernel);
#ifdef TIMING
	  ops += 2 * min_i * MIN(range_n[current + 1]  - xxx,  div_n) * min_l;
#endif
	}
	
	if (m_to - m_from == min_i) {
	  job[current].working[mypos][CACHE_LINE_SIZE * bufferside] &= 0;
	}
      }
    } while (current != mypos);
    

    for(is = m_from + min_i; is < m_to; is += min_i){
      min_i = m_to - is;

      if (min_i >= GEMM_P * 2) {
	min_i = GEMM_P;
      } else 
	if (min_i > GEMM_P) {
	  min_i = ((min_i + 1) / 2 + GEMM_UNROLL_M - 1) & ~(GEMM_UNROLL_M - 1);
	}
      
      START_RPCC();
      
      ICOPY_OPERATION(min_l, min_i, a, lda, ls, is, sa);
      
      STOP_RPCC(copy_A);
      
      current = mypos;
      do {
	
	div_n = (range_n[current + 1]  - range_n[current] + DIVIDE_RATE - 1) / DIVIDE_RATE;
	
	for (xxx = range_n[current], bufferside = 0; xxx < range_n[current + 1]; xxx += div_n, bufferside ++) {
	  
	  START_RPCC();
	  
	  KERNEL_OPERATION(min_i, MIN(range_n[current + 1] - xxx, div_n), min_l, alpha,
			   sa, (FLOAT *)job[current].working[mypos][CACHE_LINE_SIZE * bufferside],
			   c, ldc, is, xxx);
	  
	STOP_RPCC(kernel);

#ifdef TIMING
	ops += 2 * min_i * MIN(range_n[current + 1]  - xxx, div_n) * min_l;
#endif

	if (is + min_i >= m_to) {
	  /* Thread doesn't need this buffer any more */
	  job[current].working[mypos][CACHE_LINE_SIZE * bufferside] &= 0;
	  WMB;
	}
	}
	
	current ++;
	if (current >= args -> nthreads) current = 0;
	
      } while (current != mypos);
      
    }
    
  }
  
  START_RPCC();

  for (i = 0; i < args -> nthreads; i++) {
    for (xxx = 0; xxx < DIVIDE_RATE; xxx++) {
      while (job[mypos].working[i][CACHE_LINE_SIZE * xxx] ) {YIELDING;};
    }
  }

  STOP_RPCC(waiting3);

#ifdef TIMING
  BLASLONG waiting = waiting1 + waiting2 + waiting3;
  BLASLONG total = copy_A + copy_B + kernel + waiting;

  fprintf(stderr, "GEMM   [%2ld] Copy_A : %6.2f  Copy_B : %6.2f  Wait1 : %6.2f Wait2 : %6.2f Wait3 : %6.2f Kernel : %6.2f",
	  mypos, (double)copy_A /(double)total * 100., (double)copy_B /(double)total * 100.,
	  (double)waiting1 /(double)total * 100.,
	  (double)waiting2 /(double)total * 100.,
	  (double)waiting3 /(double)total * 100.,
	  (double)ops/(double)kernel / 4. * 100.);

#if 0
  fprintf(stderr, "GEMM   [%2ld] Copy_A : %6.2ld  Copy_B : %6.2ld  Wait : %6.2ld\n",
	  mypos, copy_A, copy_B, waiting);

  fprintf(stderr, "Waiting[%2ld] %6.2f %6.2f %6.2f\n",
	  mypos,
	  (double)waiting1/(double)waiting * 100.,
	  (double)waiting2/(double)waiting * 100.,
	  (double)waiting3/(double)waiting * 100.);
#endif
  fprintf(stderr, "\n");
#endif

  return 0;
}

static int gemm_driver(blas_arg_t *args, BLASLONG *range_m, BLASLONG
		       *range_n, FLOAT *sa, FLOAT *sb, BLASLONG mypos){

  blas_arg_t newarg;

  job_t          job[MAX_CPU_NUMBER];
  blas_queue_t queue[MAX_CPU_NUMBER];

  BLASLONG range_M[MAX_CPU_NUMBER + 1];
  BLASLONG range_N[MAX_CPU_NUMBER + 1];

  BLASLONG num_cpu_m, num_cpu_n;

  BLASLONG nthreads = args -> nthreads;

  BLASLONG width, i, j, k, js;
  BLASLONG m, n, n_from, n_to;
  int  mode;

#ifndef COMPLEX
#ifdef XDOUBLE
  mode  =  BLAS_XDOUBLE | BLAS_REAL | BLAS_NODE;
#elif defined(DOUBLE)
  mode  =  BLAS_DOUBLE  | BLAS_REAL | BLAS_NODE;
#else
  mode  =  BLAS_SINGLE  | BLAS_REAL | BLAS_NODE;
#endif  
#else
#ifdef XDOUBLE
  mode  =  BLAS_XDOUBLE | BLAS_COMPLEX | BLAS_NODE;
#elif defined(DOUBLE)
  mode  =  BLAS_DOUBLE  | BLAS_COMPLEX | BLAS_NODE;
#else
  mode  =  BLAS_SINGLE  | BLAS_COMPLEX | BLAS_NODE;
#endif  
#endif

  newarg.m        = args -> m;
  newarg.n        = args -> n;
  newarg.k        = args -> k;
  newarg.a        = args -> a;
  newarg.b        = args -> b;
  newarg.c        = args -> c;
  newarg.lda      = args -> lda;
  newarg.ldb      = args -> ldb;
  newarg.ldc      = args -> ldc;
  newarg.alpha    = args -> alpha;
  newarg.beta     = args -> beta;
  newarg.nthreads = args -> nthreads;
  newarg.common   = (void *)job;
   
#ifdef PARAMTEST
  newarg.gemm_p  = args -> gemm_p;
  newarg.gemm_q  = args -> gemm_q;
  newarg.gemm_r  = args -> gemm_r;
#endif

  if (!range_m) {
    range_M[0] = 0;
    m          = args -> m;
  } else {
    range_M[0] = range_m[0];
    m          = range_m[1] - range_m[0];
  }

  num_cpu_m  = 0;

  while (m > 0){
    
    width  = blas_quickdivide(m + nthreads - num_cpu_m - 1, nthreads - num_cpu_m);

    m -= width;
    if (m < 0) width = width + m;

    range_M[num_cpu_m + 1] = range_M[num_cpu_m] + width;

    num_cpu_m ++;
  }

  for (i = 0; i < num_cpu_m; i++) {
    queue[i].mode    = mode;
    queue[i].routine = inner_thread;
    queue[i].args    = &newarg;
    queue[i].range_m = &range_M[i];
    queue[i].range_n = &range_N[0];
    queue[i].sa      = NULL;
    queue[i].sb      = NULL;
    queue[i].next    = &queue[i + 1];
  }
  
  queue[0].sa = sa;
  queue[0].sb = sb;
  
  if (!range_n) {
    n_from = 0;
    n_to   = args -> n;
  } else {
    n_from = range_n[0];
    n_to   = range_n[1];
  }

  for(js = n_from; js < n_to; js += GEMM_R * nthreads){
    n = n_to - js;
    if (n > GEMM_R * nthreads) n = GEMM_R * nthreads;
    
    range_N[0] = js;

    num_cpu_n  = 0;

    while (n > 0){
      
      width  = blas_quickdivide(n + nthreads - num_cpu_n - 1, nthreads - num_cpu_n);
      
      n -= width;
      if (n < 0) width = width + n;
      
      range_N[num_cpu_n + 1] = range_N[num_cpu_n] + width;
      
      num_cpu_n ++;
    }
 
    for (j = 0; j < num_cpu_m; j++) {
      for (i = 0; i < num_cpu_m; i++) {
	for (k = 0; k < DIVIDE_RATE; k++) {
	  job[j].working[i][CACHE_LINE_SIZE * k] = 0;
	}
      }
    }
    
    queue[num_cpu_m - 1].next = NULL;

    exec_blas(num_cpu_m, queue);
  }

  return 0;
}

int CNAME(blas_arg_t *args, BLASLONG *range_m, BLASLONG *range_n, FLOAT *sa, FLOAT *sb, BLASLONG mypos){

  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); 
    return 0;
  }

  if (range_m) {
    BLASLONG m_from = *(((BLASLONG *)range_m) + 0);
    BLASLONG m_to   = *(((BLASLONG *)range_m) + 1);

    m = m_to - m_from;
  }

  if (range_n) {
    BLASLONG n_from = *(((BLASLONG *)range_n) + 0);
    BLASLONG n_to   = *(((BLASLONG *)range_n) + 1);

    n = n_to - n_from;
  }

  if ((args -> m < nthreads * SWITCH_RATIO) || (args -> n < nthreads * 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));
  }
#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

  }

  return 0;
}