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clearer comments regarding nohalo.cpp optimization

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This commit is contained in:
Nicolas Robidoux 2010-05-19 20:39:48 +00:00
parent 94c0e0bbd8
commit c4f3b8dd51
1 changed files with 7 additions and 8 deletions
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15
libvips/resample/nohalo.cpp
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@ -763,8 +763,8 @@ lbbicubic( const double c00,
* Computation of the four min and four max over 3x3 input data
* sub-blocks of the 4x4 input stencil.
*
* Surprisingly, we have not succeeded in reducing the number of
* comparisons needed by using the fact that the data comes from the
* Surprisingly, we have not succeeded in reducing the number of "?
* :" needed by using the fact that the data comes from the
* (co-monotone) method Nohalo so that it is known ahead of time
* that
*
@ -784,14 +784,13 @@ lbbicubic( const double c00,
*
* "min(b,c) <= a <= max(b,c)".)
*
* We have, however, succeeded in eliminating one flag
* computation/the use of one intermediate result. See the two
* commented out lines below.
* We have, however, succeeded in eliminating one flag computation
* (one comparison) and one use of an intermediate result. See the
* two commented out lines below.
*
* Overall, only 27 comparisons are needed (to compute 4 mins and 4
* maxes!). Without the simplication, 28 comparisoins would be used.
*
* Suggestions welcome!
* maxes!). Without the simplification, 28 comparisoins would be
* used.
*/
const double m1 = (dos_two <= dos_thr) ? dos_two : dos_thr ;
const double M1 = (dos_two <= dos_thr) ? dos_thr : dos_two ;