/usr/share/octave/packages/general-1.3.4/safeprod.m is in octave-general 1.3.4-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 | ## Copyright (C) 2008 VZLU Prague, a.s., Czech Republic
##
## This program is free software; you can redistribute it and/or modify it under
## the terms of the GNU General Public License as published by the Free Software
## Foundation; either version 3 of the License, or (at your option) any later
## version.
##
## This program is distributed in the hope that it will be useful, but WITHOUT
## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
## FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
## details.
##
## You should have received a copy of the GNU General Public License along with
## this program; if not, see <http://www.gnu.org/licenses/>.
## -*- texinfo -*-
## @deftypefn{Function File} {@var{p} =} safeprod (@var{x}, @var{dim})
## @deftypefnx{Function File} {[@var{p}, @var{e}] =} safeprod (@var{x}, @var{dim})
## This function forms product(s) of elements of the array @var{x} along the dimension
## specified by @var{dim}, analogically to @code{prod}, but avoids overflows and underflows
## if possible. If called with 2 output arguments, @var{p} and @var{e} are computed
## so that the product is @code{@var{p} * 2^@var{e}}.
## @seealso{prod,log2}
## @end deftypefn
## Author: Jaroslav Hajek <highegg@gmail.com>
function [p, e] = safeprod (x, dim)
if (nargin < 1 || nargin > 2)
print_usage ();
endif
if (nargin < 2)
if (rows(x) == 1)
dim = 2;
else
dim = 1;
endif
endif
% try the normal algorithm first
if (nargout < 2)
p = prod (x, dim);
else
p = 0;
endif
% 0, Inf and NaN are possibly problematic results. If detected, use the safe
% formula.
flag = (p == 0 | ! isfinite (p));
if (any (flag(:)))
[f, e] = log2 (x);
p = prod (f, dim);
e = sum (e, dim);
if (nargout < 2)
p = p .* 2.^e;
endif
endif
endfunction
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