[Insight-developers] Patch Set to minimize calls to GetInput/GetOutput

[Williams, Norman K]

Initial work done by Bradley Lowencamp.

http://review.source.kitware.com/#/c/6570/

This patch is passing all the regression tests.  I would welcome people
trying the patch out on their real-world code and desk-check it to see if
I missed something.

A completely unscientific benchmark -- the total time running ctest for
ITK -- shows a modest improvement in execution time; I suspect that the
actual speedup is better than this; I ran all tests instead of just
running tests that would be affected by removing the inner loop callbacks
to GetInput and GetOutput

Without Patch:
Total Test time (real) = 652.27 sec
2040.613u 168.422s 10:52.58 338.5%      0+0k 30+1724io 16130pf+0w


With Patch
Total Test time (real) = 634.32 sec
1874.695u 165.739s 10:34.64 321.5%      0+0k 0+1744io 1355pf+0w

In general, it would be better to call GetInput or GetOutput once in a
function rather than calling it over and over again, as is often the case,
but I decided that it wasn't worth the effort -- and the risk accidentally
break something -- of fixing everyplace I saw code that did this.  But
developers should keep in mind that these methods are not free, and
program accordingly.

--
Kent Williams norman-k-williams at uiowa.edu






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