[Help-gsl] what's wrong in my poly code?

[Marco Maggi]

If I run the following GNU Octave code:

real_coeffs = [1 2 3 4 5];
roots(real_coeffs)

I get:

ans =

     -1.2878 +     0.8579i
     -1.2878 -     0.8579i
     0.28782 +     1.4161i
     0.28782 -     1.4161i

if I run the following GSL code:

#include <gsl/gsl_poly.h>
#include <stdio.h>
#include <stdlib.h>


int
main (int argc, const char *const argv[])
{
  gsl_poly_complex_workspace *  w;
  double        coeffs[5] = { 1.0, 2.0, 3.0, 4.0, 5.0 };
  double        result[10];
  int           e;
  size_t        i;


  w = gsl_poly_complex_workspace_alloc(5);
  e = gsl_poly_complex_solve(coeffs, 5, w, result);
  gsl_poly_complex_workspace_free(w);

  for (i=0; i<8; i+=2)
    {
      printf("%f %f\n", result[i], result[i+1]);
    }
  return 0;
}

I get:

0.137832 0.678154
0.137832 -0.678154
-0.537832 0.358285
-0.537832 -0.358285

what am I doing wrong?

TIA

--
Marco Maggi

"They say jump!, you say how high?"
Rage Against the Machine - "Bullet in the Head"