#include "blas_extended.h"
#include "blas_extended_private.h"
void BLAS_ssum_x(int n, const float *x, int incx,
		 float *sum, enum blas_prec_type prec)

/*
 * Purpose
 * =======
 * 
 * This routine computes the summation:
 * 
 *     sum <- SUM_{i=0, n-1} x[i].
 * 
 * Arguments
 * =========
 *
 * n      (input) int
 *        The length of vector x.
 * 
 * x      (input) const float*
 *        Array of length n.
 * 
 * incx   (input) int
 *        The stride used to access components x[i].
 *
 * sum    (output) float*
 * 
 * prec   (input) enum blas_prec_type
 *        Specifies the internal precision to be used.
 *        = blas_prec_single: single precision.
 *        = blas_prec_double: double precision.
 *        = blas_prec_extra : anything at least 1.5 times as accurate
 *                            than double, and wider than 80-bits.
 *                            We use double-double in our implementation.
 *
 */
{
  static const char routine_name[] = "BLAS_ssum_x";
  switch (prec) {
  case blas_prec_single:
  case blas_prec_double:
  case blas_prec_indigenous:{

      int i, xi;
      float *sum_i = sum;
      const float *x_i = x;
      float x_elem;
      double tmp;


      /* Test the input parameters. */
      if (n < 0)
	BLAS_error(routine_name, -1, n, NULL);
      if (incx == 0)
	BLAS_error(routine_name, -3, incx, NULL);

      /* Immediate return. */
      if (n <= 0) {
	*sum_i = 0.0;
	return;
      }



      tmp = 0.0;


      if (incx < 0)
	xi = -(n - 1) * incx;
      else
	xi = 0;

      for (i = 0; i < n; i++, xi += incx) {
	x_elem = x_i[xi];
	tmp = tmp + x_elem;
      }
      *sum = tmp;



      break;
    }

  case blas_prec_extra:
    {
      int i, xi;
      float *sum_i = sum;
      const float *x_i = x;
      float x_elem;
      double head_tmp, tail_tmp;
      FPU_FIX_DECL;

      /* Test the input parameters. */
      if (n < 0)
	BLAS_error(routine_name, -1, n, NULL);
      if (incx == 0)
	BLAS_error(routine_name, -3, incx, NULL);

      /* Immediate return. */
      if (n <= 0) {
	*sum_i = 0.0;
	return;
      }

      FPU_FIX_START;

      head_tmp = tail_tmp = 0.0;


      if (incx < 0)
	xi = -(n - 1) * incx;
      else
	xi = 0;

      for (i = 0; i < n; i++, xi += incx) {
	x_elem = x_i[xi];
	{
	  double dt = (double) x_elem;
	  {
	    /* Compute double-double = double-double + double. */
	    double e, t1, t2;

	    /* Knuth trick. */
	    t1 = head_tmp + dt;
	    e = t1 - head_tmp;
	    t2 = ((dt - e) + (head_tmp - (t1 - e))) + tail_tmp;

	    /* The result is t1 + t2, after normalization. */
	    head_tmp = t1 + t2;
	    tail_tmp = t2 - (head_tmp - t1);
	  };
	}
      }
      *sum = head_tmp;

      FPU_FIX_STOP;
    }
    break;
  }
}