[Insight-developers] ImageRegionIterator performance

[Miller, James V (CRD)]

As a first step to reducing the variety of image iterators that we have in itk, I attacked the
performance of the ImageRegionIterator.  Originally, I had written this iterator to lock down an API,
with no real regard for performance. However, people have complained about its performance, so I
spent some time this afternoon optimizing the code.

My test created a 200x200x200 unsigned short image and walked a 190x190x190 region setting each pixel
to a constant value.  I compared the access of raw pointers running through a contiguous block of
memory (equivalent in size to 190x190x190) to the ImageRegionIterator before and after my
optimizations. 

Raw Pointer      Original RegionIterator     New RegionIterator
 7 seconds              63 seconds               8 seconds

These timings are on my pokey 266MHz laptop using a debug build of itk. Based on these timings, I
would say the RegionIterator is ready for prime-time.  

The optimized code has been checked into the repository


Jim Miller
_____________________________________
Computer Graphics & Systems Program
GE Corporate Research & Development
Bldg. KW, Room C218B
P.O. Box 8, Schenectady NY 12301

millerjv at crd.ge.com <mailto:millerjv at crd.ge.com> 
(518) 387-4005, Dial Comm: 8*833-4005, 
Cell: (518) 505-7065, Fax: (518) 387-6981

 <<James Miller (E-mail).vcf>> 

begin 600 James Miller (E-mail).vcf
M0D5'24XZ5D-!4D0-"E9%4E-)3TXZ,BXQ#0I..DUI;&QE<CM*86UE<PT*1DXZ
M2F%M97, at 36EL;&5R("A%+6UA:6PI#0I/4D<Z1T4 at 0V]R<&]R871E(%(F1#M%
M4TP-"E1%3#M73U)+.U9/24-%.B at U,3 at I(#,X-RTT,#`U#0I414P[5T]22SM6
M3TE#13HJ.#,S+30P,#4-"E1%3#M73U)+.T9!6#HH-3$X*2`S.#<M-CDX,0T*
M0412.U=/4DL[14Y#3T1)3D<]455/5$5$+5!224Y404),13H[0V]M<'5T97(@
M1W)A<&AI8W,@)B!3>7-T96US(%!R;V=R86T[0DQ$1R!+5RP at 4DT@0S(Q.$(]
M,$0],$%03R!";W@@.#M38VAE;F5C/0T*=&%D>3M.63LQ,C,P,3M5;FET960@
M4W1A=&5S(&]F($%M97)I8V$-"DQ!0D5,.U=/4DL[14Y#3T1)3D<]455/5$5$
M+5!224Y404),13I#;VUP=71E<B!'<F%P:&EC<R`F(%-Y<W1E;7, at 4')O9W)A
M;3TP1#TP04),1$<@2U<L(%)-($,R,3A"/3!$/3!!4$\@0F]X(#@],$0]#0H]
M,$%38VAE;F5C=&%D>2P at 3ED@,3(S,#$],$0],$%5;FET960 at 4W1A=&5S(&]F
M($%M97)I8V$-"D5-04E,.U!2148[24Y415).150Z;6EL;&5R:G9`8W)D+F=E
G+F-O;0T*4D56.C(P,#`P,3(X5#$V,C8U-EH-"D5.1#I60T%21`T*
`
end