[Octave-bug-tracker] [bug #63911] hilbert crash

[John W. Eaton]

Follow-up Comment #4, bug #63911 (project octave):

I see the following on a system with enough memory available to handle this
calculation.  Note that direct calculation of inv(hilb(50000)) fails with a
singular matrix error, and invhilb (50000) is garbage because the elements
become Inf (only 870 elements are *not* Inf).  But I don't see any crash.


octave:5> x = hilb (50000);
octave:6> y = inv (x);
warning: matrix singular to machine precision, rcond = 9.02849e-26
octave:7> y = invhilb (50000);
octave:8> size (x)
ans =

   50000   50000

octave:9> size (y)
ans =

   50000   50000

octave:10> xy = x * y;
octave:11> size (xy)
ans =

   50000   50000

octave:12> xy (1:5, 1:5)
ans =

   NaN   NaN   NaN   NaN   NaN
   NaN   NaN   NaN   NaN   NaN
   NaN   NaN   NaN   NaN   NaN
   NaN   NaN   NaN   NaN   NaN
   NaN   NaN   NaN   NaN   NaN

octave:13> y (1:5, 1:5)
ans =

   2.5000e+09  -3.1250e+18   1.3021e+27  -2.7127e+35   3.3908e+43
  -3.1250e+18   5.2083e+27  -2.4414e+36   5.4253e+44  -7.0643e+52
   1.3021e+27  -2.4414e+36   1.2207e+45  -2.8257e+53   3.7844e+61
  -2.7127e+35   5.4253e+44  -2.8257e+53   6.7279e+61  -9.1982e+69
   3.3908e+43  -7.0643e+52   3.7844e+61  -9.1982e+69   1.2775e+78

octave:14> sum (isnan (xy(:)))
ans = 2.5000e+09
octave:15> sum (isnan (y(:)))
ans = 0
octave:16> sum (isinf (y(:)))
ans = 2.5000e+09
octave:17> sum (isinf (x(:)))
ans = 0
octave:18> y(end-10:end,end-10:end)
ans =

   Inf  -Inf   Inf  -Inf   Inf  -Inf   Inf  -Inf   Inf  -Inf   Inf
  -Inf   Inf  -Inf   Inf  -Inf   Inf  -Inf   Inf  -Inf   Inf  -Inf
   Inf  -Inf   Inf  -Inf   Inf  -Inf   Inf  -Inf   Inf  -Inf   Inf
  -Inf   Inf  -Inf   Inf  -Inf   Inf  -Inf   Inf  -Inf   Inf  -Inf
   Inf  -Inf   Inf  -Inf   Inf  -Inf   Inf  -Inf   Inf  -Inf   Inf
  -Inf   Inf  -Inf   Inf  -Inf   Inf  -Inf   Inf  -Inf   Inf  -Inf
   Inf  -Inf   Inf  -Inf   Inf  -Inf   Inf  -Inf   Inf  -Inf   Inf
  -Inf   Inf  -Inf   Inf  -Inf   Inf  -Inf   Inf  -Inf   Inf  -Inf
   Inf  -Inf   Inf  -Inf   Inf  -Inf   Inf  -Inf   Inf  -Inf   Inf
  -Inf   Inf  -Inf   Inf  -Inf   Inf  -Inf   Inf  -Inf   Inf  -Inf
   Inf  -Inf   Inf  -Inf   Inf  -Inf   Inf  -Inf   Inf  -Inf   Inf
octave:19> sum (!isinf (y(:)))
ans = 870


By "crash" what does the OP mean?  An error message?  I would expect that on a
system with insufficient memory, so that's not a bug.  Or a segfault or some
other thing that causes Octave to exit?  That might be a bug.  But without
more info, I agree we should close this report as invalid.


    _______________________________________________________

Reply to this item at:

  <https://savannah.gnu.org/bugs/?63911>

_______________________________________________
Message sent via Savannah
https://savannah.gnu.org/