Opencv ocl library performance problem and sample square code performance question??

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While i was Studying OpenCV and OpenCL (in OpenCV OCL Library), I had ocurred problem in ocl library and square sample code performance.

I think that GPU mode(OCL, OpenCL) performance more faster than CPU mode performance, but My Test result differ.
My Test is comparison in Square sample findsquares function time and in finsquare function used ocl library performance time
but hog_ocl is GPU Mode faster than CPU Mode
why don't know that......??...

Square Sample "findsquares" fucntion result time

ocl Sample performance_ocl result time in square sample is used ocl function

My Test Enviroment :
- CPU : AMD E-350 Processor
- GPU : ATI Radeon HD 6310
- Memory : 4GB
- OS : Ubuntu 12.04 LTS
- OpenCL Usable : Yes
- OpenCV Version : 2.4.4