[Octave-bug-tracker] [bug #55100] [octave forge] (image) Unit test in normxcorr2 fails randomly

[Avinoam Kalma]

Follow-up Comment #3, bug #55100 (project octave):

I thought also that factor of 4 will suffice, but using the following simple
script


Nm = 0;
cnt = 0;
for i=1:10000000
a = rand (10, 10);
c = normxcorr2 (a(5:7, 6:9), a);
f = abs(c(7,9)-1)/eps;
if (f > 20)
    cnt++;
    fprintf (" i = %d cnt = %d f = %g\n", i, cnt, f);
end    
if (f > Nm)
  Nm = f;
  fprintf (" i = %d Nm = %g\n", i, Nm);
end
end


shows that if I make 10,000,000 tests, the factor should be 42 (the answer
to...), and in 21 cases out of 10,000,000,  a factor of 20 will not suffice. 
The question is if we can allow a few random failures (21 out of 10,000,000 is
realy negligible), or we should use a factor that the test will never fail.


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