OpenBLAS/lapack/getf2/zgetf2_k.c

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/* Copyright 2009, 2010 The University of Texas at Austin.           */
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#include <stdio.h>
#include <float.h>
#include "common.h"

double fabs(double);

static FLOAT dp1 =  1.;
static FLOAT dm1 = -1.;

blasint CNAME(blas_arg_t *args, BLASLONG *range_m, BLASLONG *range_n, FLOAT *sa, FLOAT *sb, BLASLONG myid) {

  BLASLONG m, n, lda, offset;
  blasint *ipiv;
  FLOAT *a;

  FLOAT temp1, temp2, temp3, temp4, ratio, den;
  blasint i, j;
  blasint ip, jp;
  blasint info;
  BLASLONG len;
  FLOAT *b;

  m    = args -> m;
  n    = args -> n;
  a    = (FLOAT *)args -> a;
  lda  = args -> lda;
  ipiv = (blasint *)args -> c;
  offset = 0;

  if (range_n) {
    m     -= range_n[0];
    n      = range_n[1] - range_n[0];
    offset = range_n[0];
    a     += range_n[0] * (lda + 1) * COMPSIZE;
  }

  info = 0;
  b = a;

  for (j = 0; j < n; j++) {

    len = MIN(j, m);

    for (i = 0; i < len; i++) {
      ip = ipiv[i + offset] - 1 - offset;
      if (ip != i) {
	temp1 = *(b + i  * 2 + 0);
	temp2 = *(b + i  * 2 + 1);
	temp3 = *(b + ip * 2 + 0);
	temp4 = *(b + ip * 2 + 1);
	*(b + i  * 2 + 0) = temp3;
	*(b + i  * 2 + 1) = temp4;
	*(b + ip * 2 + 0) = temp1;
	*(b + ip * 2 + 1) = temp2;
      }
    }

    ZTRSV_NLU(len, a, lda, b, 1, sb);

    if (j < m) {
      GEMV_N(m - j, j, 0, dm1,  ZERO, a + j * 2, lda, b, 1, b + j * 2, 1, sb);

      jp = j + IAMAX_K(m - j, b + j * 2, 1);
      if (jp>m) jp = m;        //avoid out of boundary
      ipiv[j + offset] = jp + offset;
      jp--;

      temp1 = *(b + jp * 2 + 0);
      temp2 = *(b + jp * 2 + 1);

  //    if ((temp1 != ZERO) || (temp2 != ZERO)) {
	if ((fabs(temp1) >= DBL_MIN) || (fabs(temp2) >= DBL_MIN)) {
		
	if (jp != j) {
	  SWAP_K(j + 1, 0, 0, ZERO, ZERO, a + j * 2, lda,
		 a + jp * 2, lda, NULL, 0);
	}

	if (fabs(temp1) >= fabs(temp2)){
	  ratio = temp2 / temp1;
	  den = dp1 /(temp1 * ( 1 + ratio * ratio));
	  temp3 =  den;
	  temp4 = -ratio * den;
	} else {
	  ratio = temp1 / temp2;
	  den = dp1 /(temp2 * ( 1 + ratio * ratio));
	  temp3 =  ratio * den;
	  temp4 = -den;
	}

	if (j + 1 < m) {
	  SCAL_K(m - j - 1, 0, 0, temp3, temp4,
		 b + (j + 1) * 2, 1, NULL, 0, NULL, 0);
	}
      } else {
	if (!info) info = j + 1;
      }
    }
    b += lda * 2;
  }
  return info;

}