Weird behavior of ocl matrix in opencv

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Hi,

I am faciong a qweird problem. I have two matrix, input and output. For each element i in a row r in the input matrix, it sums all element before i in that row and put the sum in i th column and r th row in output matrix. When I do this for small matrix, it gives me no problem. But for a big matrix (604x454), the output matrix contains GRARBAGE value in all output matrix rows except the first row.

"__kernel void "
            "  v2_integral_cols_sum(__global uchar *src,\n"
                    "int rows,int cols,__global int *lm_sum, int pixels,int steps,int o_steps)\n"
                    "{\n"

                "int gid=get_global_id(0);\n"
                "if(gid>=pixels)"
                "return;\n"
                "else \n"
                "{"
                "int x = gid % steps;\n"
                "int y = gid / steps;\n"
                "int sum=0;\n"


                "for (int i=0;i<=x;i++)"
                "{\n"
                    "sum=sum+src[y * steps + i];\n"
                "}\n"

            "lm_sum[y*o_steps + x]=sum;\n"


        "}"

    "}\n"

interestingly if I use the printf statement after the output assignment statement as in this block,I get correct output matrix. I do not find any explanation of this weird behavior. Anyone can help me?

"lm_sum[y*o_steps + x]=sum;\n"
 "if(gid==640)\n"
            "{"

            "printf(\"lm_sum [%d %d %d] %d  \",x,y,gid,lm_sum[y * o_steps+ x]);\n"


            "}\n"