 
  desc: When gpu program is loaded, you can only edit default param.
        When gpu program is unloaded, you can only edit basic parameter.
  			
  			Be careful with unload, it will do following things:
  			
  			1.temporarily remove default_param, if you save and exit now. 
  			  you will lost default_param, gpu program ref also will be blank.
  	
  			2.temporarily remove param setting of releated pass gpu program ref,
  			  if you save and exit now. you will lost all param setting.
  			  
  			Make sure you execute loadGpu after you finish setting. 
  			loadGpu will set back previous setting as much as possible.
  			
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  format: unloadGpuProgram
