<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"><base href="x-msg://2040/"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Marius,<div><br></div><div>Sound like a great idea! Those are some great looking numbers. Also keep in mind that I got rather difference performance for different types with fill.</div><div><br></div><div>Using std::copy, and std::fill are both good things. Keep an eye out for usage of std::copy too, that can have even bigger change in performance.</div><div><br></div><div>Brad</div><div><br><div><div>On Apr 10, 2013, at 8:26 AM, <<a href="mailto:M.Staring@lumc.nl">M.Staring@lumc.nl</a>> wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div lang="EN-US" link="blue" vlink="purple" style="font-family: Helvetica; font-size: medium; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; "><div class="WordSection1" style="page: WordSection1; "><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">Hi Brad,<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; "><o:p> </o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">I saw your gerrit topic<span class="Apple-converted-space"> </span><a href="http://review.source.kitware.com/#/c/10762/" style="color: purple; text-decoration: underline; ">http://review.source.kitware.com/#/c/10762/</a><o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">And I wondered whether such a change would have implications elsewhere in the toolkit, most notably the image registration framework where array.Fill(0) is used quite a lot for initialization of derivatives and transform parameters.<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; "><o:p> </o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">So, I did a test, see the attached code, to compare an itk.Fill with a standard C fill using a for loop, with a C++ fill using std::fill_n. The results are in favour of the C++ way, for a tested array size between 1e2 and 1e7.<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; "><o:p> </o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">On my Win7 64bit machine using VS2008:<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; "><o:p> </o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">Array size = 100, repetitions = 20000000<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">The elapsed time for a itk.Fill 2483 ms.<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">The elapsed time for a C fill 4748 ms.<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">The elapsed time for a C++ fill_n 543 ms.<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; "><o:p> </o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">Array size = 1000, repetitions = 2000000<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">The elapsed time for a itk.Fill 2418 ms.<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">The elapsed time for a C fill 4585 ms.<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">The elapsed time for a C++ fill_n 404 ms.<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; "><o:p> </o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">Array size = 10000, repetitions = 200000<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">The elapsed time for a itk.Fill 2534 ms.<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">The elapsed time for a C fill 4605 ms.<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">The elapsed time for a C++ fill_n 618 ms.<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; "><o:p> </o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">Array size = 100000, repetitions = 20000<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">The elapsed time for a itk.Fill 2553 ms.<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">The elapsed time for a C fill 4593 ms.<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">The elapsed time for a C++ fill_n 580 ms.<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; "><o:p> </o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">Array size = 1000000, repetitions = 2000<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">The elapsed time for a itk.Fill 2605 ms.<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">The elapsed time for a C fill 4665 ms.<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">The elapsed time for a C++ fill_n 1284 ms.<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; "><o:p> </o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">Array size = 10000000, repetitions = 200<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">The elapsed time for a itk.Fill 3289 ms.<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">The elapsed time for a C fill 4780 ms.<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">The elapsed time for a C++ fill_n 1168 ms.<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; "><o:p> </o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">---<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">On my linux Ubuntu with gcc 4.6.3:<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; "><o:p> </o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">Array size = 100, repetitions = 20000000<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">The elapsed time for a itk.Fill 1870000 ms.<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">The elapsed time for a C fill 1660000 ms.<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">The elapsed time for a C++ fill_n 490000 ms.<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; "><o:p> </o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">Array size = 1000, repetitions = 2000000<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">The elapsed time for a itk.Fill 1520000 ms.<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">The elapsed time for a C fill 1520000 ms.<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">The elapsed time for a C++ fill_n 390000 ms.<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; "><o:p> </o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">Array size = 10000, repetitions = 200000<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">The elapsed time for a itk.Fill 1510000 ms.<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">The elapsed time for a C fill 1500000 ms.<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">The elapsed time for a C++ fill_n 380000 ms.<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; "><o:p> </o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">Array size = 100000, repetitions = 20000<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">The elapsed time for a itk.Fill 1500000 ms.<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">The elapsed time for a C fill 1500000 ms.<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">The elapsed time for a C++ fill_n 440000 ms.<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; "><o:p> </o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">Array size = 1000000, repetitions = 2000<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">The elapsed time for a itk.Fill 1500000 ms.<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">The elapsed time for a C fill 1500000 ms.<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">The elapsed time for a C++ fill_n 510000 ms.<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; "><o:p> </o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">Array size = 10000000, repetitions = 200<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">The elapsed time for a itk.Fill 1530000 ms.<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">The elapsed time for a C fill 1520000 ms.<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">The elapsed time for a C++ fill_n 1100000 ms.<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; "><o:p> </o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; "><o:p> </o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">I did not further test this on the effect on registration, but changing the itk::Array::Fill function to use std::fill_n may be a nice idea.<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">What do you think?<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; "><o:p> </o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">Marius<o:p></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; "><o:p> </o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; "><span lang="EN-GB">Marius Staring, PhD<o:p></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; "><span lang="EN-GB">Division of Image Processing (LKEB)<o:p></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; "><span lang="EN-GB">Department of Radiology<o:p></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; "><span lang="EN-GB">Leiden University Medical Center<o:p></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; "><span lang="EN-GB">PO Box 9600, 2300 RC Leiden, The Netherlands<o:p></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; "><span lang="EN-GB">phone: +31 (0)71 526 2137, fax: +31 (0)71 524 8256<o:p></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; "><span lang="EN-GB"><a href="mailto:m.staring@lumc.nl" style="color: purple; text-decoration: underline; ">m.staring@lumc.nl</a><o:p></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; "><o:p> </o:p></div></div><span><CMakeLists.txt></span><span><test.cxx></span></div></blockquote></div><br></div></body></html>