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cio7

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12-04-2009
02:53 AM

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ippiCrossCorrValid_NormLevel_8u32f performance issue

While evaluating Ipp6.1 version (x86, 32bit) I have noticed that the

ippiCrossCorrValid_NormLevel_8u32f performs significantly slower (2-3 times) than

ippiCrossCorrValid_Norm_8u32f function on identical input.

Furthermore, it does perform slower than the ippiCrossCorrValid_NormLevel_8u32f from version IPP5.1.

The behaviour was identical on both Intel Core2Duo and Intel Atom processors.

The difference in performance is somewhat dependent on the actual size parameters for source and template.

Any information on this topic would be wellcome.

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PaulF_IntelCorp

Employee

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09-17-2010
05:02 PM

87 Views

I suspect this has to do with differences in the nature of the calculation. The two are described below, note that the significant difference is the "cross-correlation value" that is calculated. The formulae are nearly identical, but one involves substantially more calculations than the other.

Go to this page:

http://software.intel.com/sites/products/documentation/hpc/ipp/ippi/ippi_ch11/ch11_image_proximity_m...

in the documentation to see a detailed description of the two different correlation values:_{tx}(r,c) and_{tx}(r,c)

The function ippiCrossCorrValid_Norm is declared in the ippi.h file. It operates with ROI (see Regions of Interest in Intel IPP). This function computes the normalized cross-correlation values _{tx}(r,c) for the pixels of the source image without zero-padded edges. The size of the resulting matrix with normalized cross-correlation values is

(W_{s} - W_{t} + 1) * (H_{s} - H_{t} + 1),

where W_{s} , H_{s} denote the width and height of the source image, and W_{t} , H_{t} denote the width and height of the template. The template anchor for matching the image pixel is always at the geometric center of the template. (See the formula for _{tx}(r,c) in section Image Proximity Measures).

The function ippiCrossCorrValid_NormLevel is declared in the ippi.h file. It operates with ROI (see Regions of Interest in Intel IPP). This function computes the normalized correlation coefficients _{tx}(r,c) for the pixels of the source image without zero-padded edges. The size of the resulting matrix with normalized correlation coefficients is

(W_{s} - W_{t} + 1) * (H_{s} - H_{t} + 1),

where W_{s} , H_{s} denote the width and height of the source image, and W_{t} , H_{t} denote the width and height of the template. The template anchor for matching the image pixel is always at the geometric center of the template. (See the formula for _{tx}(r,c) in section Image Proximity Measures).

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