Понимание поведения глобального идентификатора в OpenCL

Question

OpenCL новичок вопрос

Я пытаюсь написать ядро, чтобы выполнить задачу более прямоугольные области изображения.

OpenCL

__kernel void GrayBlockSignalSeparation 
(
    __global float * rhos 
) 
{ 
    const int neighbourhoodSize = 60; 

    const int x = get_global_id(0); 
    const int y = get_global_id(1); 

    rhos[x - 1 + (y-1)*(neighbourhoodSize) ] = x; 
} 

C#

private static void GraySignalSeparation 
(       
    ref Image<Gray, float> Signal 
) 
{ 
    float[] rhos = new float[(int)(image.Width/60) * (int)(image.Height/60)];     
    CLCalc.Program.Variable rhosVar = new CLCalc.Program.Variable(rhos); 

    CLCalc.Program.MemoryObject[] args = new CLCalc.Program.MemoryObject[] 
    {      
     rhosVar 
    }; 
    GraySignalSeparationKernel.Execute(args, new int[] { (int)(image.Width/60), (int)(image.Height/60) }); 

    rhosVar.ReadFromDeviceTo(rhos); 

} 

Когда я проверить значения Rho в отладчике я считаю, что некоторые из них, по всей видимости, были упущены и установлены равными нулю.

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Answer 1

Попробуйте это:

rhos[x + (y)*(correct_stride) ] = x; 

где correct_stride = image.Width/60;

Глобальные идентификаторы индексируются от 0 до. Он формирует последовательность, например, 0,1,2,3,4 ... и не 1,2,3,4 ... Если мы строги, вы вызываете неопределенное поведение, так как ваш первый индекс выполняет запись за пределами памяти, которую вы первоначально выделены.

Также

float[] rhos = new float[(int)(image.Width/60) * (int)(image.Height/60)]; 

меня беспокоит немного. Ваше изображение точно 3600x3600? В противном случае ваш шаг неправильный. Переменная neighbourhoodsize должна быть шириной используемого сегмента изображения.