Re: fast hist() / histogram() implementation in C++

[Paul Kienzle]

Here are the tests from hist.m in octave:

%!test
%!  [nn,xx]=hist([1:4],3);
%!  assert(xx, [1.5,2.5,3.5]);
%!  assert(nn, [2,1,1]);
%!test
%!  [nn,xx]=hist([1:4]',3);
%!  assert(xx, [1.5,2.5,3.5]');
%!  assert(nn, [2,1,1]');
%!test
%!  [nn,xx]=hist([[1:4]',[1:4]'],3);
%!  assert(xx, [[1.5,2.5,3.5]',[1.5,2.5,3.5]']);
%!  assert(nn, [[2,1,1]',[2,1,1]']);
%!assert(hist(1,1),1);
%!test
%!  for n = [10, 30, 100, 1000]
%!    assert( sum(hist([1:n], n)), n );
%!    assert( sum(hist([1:n], [2:n-1])), n);
%!    assert( sum(hist([1:n], [1:n])), n );
%!    assert( sum(hist([1:n], 29)), n);
%!    assert( sum(hist([1:n], 30)), n);
%!  endfor


Here's the result from your hist function:

>>>>> processing hist
>>>>> /Users/paulkienzle/Downloads/histc-Nov05/hist.m
  ***** test
  [nn,xx]=hist([1:4],3);
  assert(xx, [1.5,2.5,3.5]);
  assert(nn, [2,1,1]);
!!!!! test failed
error: assert (nn,[2, 1, 1]) expected
  2  1  1
but got
  1  1  2
maximum absolute error 1 exceeds tolerance 0
  ***** test
  [nn,xx]=hist([1:4]',3);
  assert(xx, [1.5,2.5,3.5]');
  assert(nn, [2,1,1]');
!!!!! test failed
error: assert (xx,[1.5, 2.5, 3.5]') expected
  1.5000
  2.5000
  3.5000
but got
  1.5000  2.5000  3.5000
Dimensions don't match
  ***** test
  [nn,xx]=hist([[1:4]',[1:4]'],3);
  assert(xx, [[1.5,2.5,3.5]',[1.5,2.5,3.5]']);
  assert(nn, [[2,1,1]',[2,1,1]']);
!!!!! test failed
error: assert (xx,[[1.5, 2.5, 3.5]', [1.5, 2.5, 3.5]']) expected
  1.5000  1.5000
  2.5000  2.5000
  3.5000  3.5000
but got
  1.5000  2.5000  3.5000
Dimensions don't match
  ***** assert(hist(1,1),1);
!!!!! test failed
error: first argument must be real vector or matrix
  ***** test
  for n = [10, 30, 100, 1000]
    assert( sum(hist([1:n], n)), n );
    assert( sum(hist([1:n], [2:n-1])), n);
    assert( sum(hist([1:n], [1:n])), n );
    assert( sum(hist([1:n], 29)), n);
    assert( sum(hist([1:n], 30)), n);
  endfor
PASSES 1 out of 5 tests

On Nov 5, 2004, at 1:30 PM, Petr Mikulik wrote:

> > > I acknowledge the effort in improving hist.m. Is is as fast as 
> > > M-language
> > > allows. Unfortunately, using it for large images (e.g. 2D detector 
> > > data)
> > > like 512^2 and above goes beyond the user patiency (at least, for 
> > > me). That
> > > was my move to reimplement my own favourite histogram.m into 
> > > histogram.oct.
> > > ...
> > > Thus, in average, 50x speedup is achieved for linearly spaced bins,
> > > and 27x for logarithmically (or whichever non-linearly) spaced bins.
> >
> > These improvements do appear to be impressive.
> >
> > I would recommend that you contribute them to octave-forge,
> > probably in the main/general directory.
> >
> > Additionally, you can ask jwe if he is prepared to add them to
> > octave.
>
>
> I've implemented histogram evaluation in C++: routine histc.cc, and its
> corresponding hist.m.
>
> Get it from here:
>         http://www.physics.muni.cz/~mikulik/tmp/histc-Nov05.zip
>
> It supports histogram of a vector and 2D matrix.
> I don't know how to access dimensions for N-dim matrices. Someone can
> contribute the missing code?
>
> Thus I ask -- what do you think -- could this replace hist.m, and 
> contribute
> the missing histc function in the Octave package?
>
> Petr
>
>
>
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