[vtkusers] timings for vtkImageReader2

[Budd Hirons]

3 seconds! you have to let me in on your secret!

UltraATA maximum transfer in the DMA mode 5 is only 100MB/s, so I guess 
it is possible, but unlikely, to read this in 3 seconds.  I ran this 
exercise on two machines, compiled from C++.

machine 1 (p4,ultraATA drive on board,DMA,DDR ram) - 18s read
machine 2 (dual Xeon,SCSI on PCI adapter,no DMA,pc133 ram) - 66s read

We regularly deal with volumes that exceed this one in size, and range 
to 800 megs on disk.  Load times to get very large chunks of data into 
can ram vary wildly, but it should not be expected to happen 
instantaneously.  45 seconds for larger datasets would not be off the 
mark in release on random equipment and with other processes likely running.

Cheers,
Budd.



Kate Kerekes wrote:
> Hello again,
> 
> I apologize for the length of this message.  I am still having problems with
> the time it takes vtkImageReader2 to read 268 MB of data (a series of 512
> files with 512x512 shorts each.)  I ran the following test program (from
> Mathieu Malaterre  translated to tcl by me) to see how long a read takes:
> 
> #!/bin/sh
> load vtkCommonTCL.dll
> load vtkFilteringTCL.dll
> load vtkGraphicsTCL.dll
> load vtkIOTCL.dll
> load vtkImagingTCL.dll
> load vtkRenderingTCL.dll
> load vtkHybridTCL.dll
> source Interactor.tcl
> source bindings-rw.tcl
> source bindings-iw.tcl
> source bindings.tcl
> source setget.tcl
>  
> console show
> 
> set createImage yes
> 
> if {$createImage=="yes"} {
> vtkImageNoiseSource noise
>    noise SetWholeExtent 0 511 0 511 0 511
>    noise SetMinimum 0.0
>    noise SetMaximum 1.0
>    [noise GetOutput] ReleaseDataFlagOn
>    puts "about to update vtkImageNoiseSource"
>    noise Update
>    puts "finished updating vtkImageNoiseSource"
>  
>    vtkImageCast cast
>    cast SetInput [noise GetOutput]
>    cast SetOutputScalarTypeToUnsignedShort 
>  
>    vtkImageWriter writer
>    writer SetInput [cast GetOutput]
>    writer SetFileDimensionality 3
>    writer SetFileName "bench.img"
>    puts "about to update writer"
>    writer Write
>    puts "finished updating writer"
> }
>  
>    vtkImageReader2 reader
>    [reader GetOutput] ReleaseDataFlagOn
>    reader SetDataExtent 0 511 0 511 0 511
>    reader SetDataScalarTypeToUnsignedShort
>    reader SetDataByteOrderToLittleEndian
>    reader SetFileName "bench.img"
> 
>    puts "about to update reader"
>    set time1 [clock clicks -milliseconds]
>    reader Update
>    set time2 [clock clicks -milliseconds]
>    puts "finished updating reader"
>    puts "reader update took [expr $time2-$time1] milliseconds"
> 
> The read takes 15 seconds on my machine (Windows XP with service pack 2, AMD
> athlon 64 chipset 3000+, with 512 megs of memory).  I am reading data from
> the IDE harddrive.  Mathieu's timing was 3 seconds.  This of course is not
> the newest machine out there, but it is not that old either.
> 
> Then when I try to read my series of slices, my machine takes 45 seconds.
> The only difference in reading the slice files and the bench.img created by
> ImageNoiseSource is that the bench.img is all three dimensions in one file
> (rather than a series of slices), and the bench.img file uses unsigned
> shorts rather than shorts (but both are 2 bytes, right?).
> 
> So here are my thoughts as to why the problem could be occurring--any
> feedback would be appreciated:
> 1.  my computer is too slow--I don't think this is it
> 2.  the bench.img file only reads faster because it has just been written to
> memory and is probably still in the cache and therefore takes less time to
> access
> 3.  the fact that my slices are in series and 512 different files have to be
> read is the slow down
> 4.  the code running in tcl is slower than code running in c (I can fix this
> by calling a c function from tcl--but only if I think this is really the
> problem)
> 5.  there is some other problem that I am unaware of--this is my worst fear
> :(
> 
> Please help!  All of the other feedback I have gotten before says that the
> read should take no more than a few seconds.  45 seconds is way too long for
> our customer and this is not even the largest filesize that will be used.
> 
> Thanks,
> Kate Kerekes
> 
> 
> 
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