That's pretty sweet.
I wondered about this the other day: You can't use std::copy directly on
types that could in theory benefit from it. For example:
#include <algorithm>
#include <iostream>
#include "itkVector.h"
int main(int argc, char *argv[])
{
typedef itk::Vector<double, 32> VecType;
VecType a, b;
// this won't work
std::copy(a,a.end(),b);
// this works but is fugly
std::copy(a.GetDataPointer(),
a.GetDataPointer()+VecType::Dimension,
b.GetDataPointer());
}
Would it add unacceptable ugliness to support std::algorithm copy
semantics?
--
Kent Williams [email protected]
On 5/8/13 7:37 AM, "Bradley Lowekamp" <[email protected]> wrote:
>
>
>
>Hello,
>
>
>I know the CastImageFilter is no the most exciting filter but, it's
>probably the most frequently used and should be as snappy as possible.
>And the lessons learn here should be applicable to many other places.
>
>
>I am clamming that I have speed this guy up by 5-25X from ITK v4.3.2 when
>the following two patch are combined:
>
>
>http://review.source.kitware.com/#/c/11174/
>http://review.source.kitware.com/#/c/11163/
>
>
>
>I have to thank Kent for motivating the use of using std:copy for
>conversion to get most of this gain, in ImageAlgorithm::Copy.
>
>
>The following performance was measure by converting short to float, with
>the following loop:
>
>
>const unsigned int cnt = 5;
>
>
> for ( unsigned int j = 0; j < 10; ++j )
> {
> t.Start();
> for ( unsigned int i = 0; i < cnt; ++i )
> {
> inImage1->Modified();
> f->Update();
> }
> t.Stop();
> }
>
>
> std::cout << "\t+Add Average Time: " << t.GetMean()/cnt << t.GetUnit()
><< std::endl;
>
>
>
>
>
>I hope the follow table get formatted OK over e-mail:
>
>
>gcc 4.4.74.3.2masterw/ std::copymaster speedupincremental speeduptotal
>speedup[64, 64,
>64]0.00230210.00072730.00012913.165104825.63317275717.82958224[128, 128,
>128]0.01696210.00433210.00101023.9154090134.2882285416.79016867[256, 256,
>256]0.14184400.03067570.02385984.6239857611.2856645915.94489476[32,
>32]0.00001410.00000640.00000372.1828232231.7320512033.780761589[64,
>64]0.00003640.00001160.00000343.128445423.41794490910.6928541[128,
>128]0.00012510.00003190.00000773.9209226224.16303764816.32294849[256,
>256]0.00046880.00010400.00001904.509772995.46965017624.66688063gcc
>4.7.1[64, 64,
>64]0.001622900.00049710.00012433.2649981893.99942067713.05810127[128,
>128,
>128]0.011172400.00222670.00095295.0174247322.33688300211.72513457[256,
>256, 256]0.089189000.02281310.02360303.9095519680.9665339153.77871457[32,
>32]0.000011200.00000580.00000361.9167268711.6311584593.126485249[64,
>64]0.000026280.00000750.00000323.483567442.3718157528.262380129[128,
>128]0.000087600.00001400.00000746.2571732661.89174800111.83699502[256,
>256]0.000317160.00003170.000019110.005110391.65661205616.5745865icc
>13.0.1[64, 64,
>64]0.00187010.0012090.0001301621.5468320939.28842519314.36763418[128,
>128,
>128]0.01223670.0079420.0009915831.5408278398.00905219212.34057058[256,
>256, 256]0.09650670.0603450.01903721.5992387163.1698674175.069374698[32,
>32]0.00001140.0000093.28E-061.2467412812.7921503123.481089056[64,
>64]0.00003010.0000183.22E-061.7153699545.4444565279.339257142[128,
>128]0.00010300.0000629.04E-061.6631539176.85224533711.39633867[256,
>256]0.00039610.0002212.05E-051.79448405810.7557825119.30108025
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