OpenBLAS/lapack/getf2/getf2_k.c

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#include <stdio.h>
#include <float.h>
#include "common.h"

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;
  blasint *ipiv, offset;
  FLOAT *a;

  FLOAT temp1, temp2;
  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);
	temp2 = *(b + ip);
	*(b + i) = temp2;
	*(b + ip) = temp1;
      }
    }

    for (i = 1; i < len; i++) {
      b[i] -= DOTU_K(i, a + i, lda, b, 1);
    }

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

      jp = j + IAMAX_K(m - j, b + j, 1);
      if (jp>m) jp = m;        //avoid out of boundary when the iamax kernel does not cope with NaN in input, see gh issue 723
      ipiv[j + offset] = jp + offset;
      jp--;
      temp1 = *(b + jp);

      if (temp1 != ZERO) {
#if defined(DOUBLE)
	if (fabs(temp1) >= DBL_MIN ) {
#else
	if (fabs(temp1) >= FLT_MIN ) {
#endif
  	  temp1 = dp1 / temp1;

	  if (jp != j) {
	    SWAP_K(j + 1, 0, 0, ZERO, a + j, lda, a + jp, lda, NULL, 0);
	  }
	  if (j + 1 < m) {
	    SCAL_K(m - j - 1, 0, 0, temp1, b + j + 1, 1, NULL, 0, NULL, 0);
	  }
        }
      } else {
	if (!info) info = j + 1;
      }
    }
    b += lda;
  }
  return info;
}