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comparison scripts/general/nextpow2.m @ 25236:69b21b8a0e9f

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nextpow2.m: Compute value correctly for Inf or NaN inputs (bug #53463). * nextpow2.m: Change docstring to define the output variable N. Check for failure of 2-input form of log2 function by looking for an exponent of 0. If found, copy over the value that log2 was not able to process (e.g., Inf or NaN). Add BIST tests for special cases. Add fail pattern to %!error test.
author Rik <rik@octave.org>
date Thu, 12 Apr 2018 14:34:10 -0700
parents 6652d3823428
children 996d78102a71
comparison
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25235:27e6b38571d3 25236:69b21b8a0e9f
15 ## You should have received a copy of the GNU General Public License 15 ## You should have received a copy of the GNU General Public License
16 ## along with Octave; see the file COPYING. If not, see 16 ## along with Octave; see the file COPYING. If not, see
17 ## <https://www.gnu.org/licenses/>. 17 ## <https://www.gnu.org/licenses/>.
18 18
19 ## -*- texinfo -*- 19 ## -*- texinfo -*-
20 ## @deftypefn {} {} nextpow2 (@var{x}) 20 ## @deftypefn {} {@var{n} =} nextpow2 (@var{x})
21 ## Compute the exponent for the smallest power of two larger than the input. 21 ## Compute the exponent for the smallest power of two larger than the input.
22 ## 22 ##
23 ## For each element in the input array @var{x}, return the first integer 23 ## For each element in the input array @var{x}, return the first integer
24 ## @var{n} such that 24 ## @var{n} such that
25 ## @tex 25 ## @tex
45 if (! isnumeric (x)) 45 if (! isnumeric (x))
46 error ("nextpow2: X must be numeric"); 46 error ("nextpow2: X must be numeric");
47 endif 47 endif
48 48
49 [f, n] = log2 (abs (x)); 49 [f, n] = log2 (abs (x));
50 n(f == 0.5)--; 50 idx = (n == 0); # Find any failures of log2 function (n == 0)
51 n(idx) = f(idx); # and copy over value.
52 n(f == 0.5)--;
51 53
52 endfunction 54 endfunction
53 55
54 56
55 %!assert (nextpow2 (16), 4) 57 %!assert (nextpow2 (16), 4)
57 %!assert (nextpow2 (31), 5) 59 %!assert (nextpow2 (31), 5)
58 %!assert (nextpow2 (-16), 4) 60 %!assert (nextpow2 (-16), 4)
59 %!assert (nextpow2 (-17), 5) 61 %!assert (nextpow2 (-17), 5)
60 %!assert (nextpow2 (-31), 5) 62 %!assert (nextpow2 (-31), 5)
61 %!assert (nextpow2 (1:17), [0 1 2 2 3 3 3 3 4 4 4 4 4 4 4 4 5]) 63 %!assert (nextpow2 (1:17), [0 1 2 2 3 3 3 3 4 4 4 4 4 4 4 4 5])
64 ## Special cases
65 %!assert (nextpow2 (0), 0)
66 %!assert (nextpow2 (1), 0)
67 %!assert (nextpow2 (Inf), Inf)
68 %!assert (nextpow2 (-Inf), Inf)
69 %!assert (nextpow2 (NaN), NaN)
70 %!assert (nextpow2 ([1, Inf, 3, -Inf, 9, NaN]), [0, Inf, 2, Inf, 4, NaN])
62 71
72 ## Test input validation
63 %!error nexpow2 () 73 %!error nexpow2 ()
64 %!error nexpow2 (1, 2) 74 %!error nexpow2 (1, 2)
75 %!error <X must be numeric> nextpow2 ("t")