2 Replies Latest reply on Dec 7, 2010 6:36 PM by himanshu.gautam

    How costly are type casts?

    FrodoTheGiant

      Hi,

      I have a kernel that is using data from a lookup table to initialize an array.

      Output data has to be of type float.

      To save __constant memory I use type "char" for the data in the lookup table (is OK since the values only go from -16 to +16).

       

      __constant char lookup_table[16] = {-12, 2, 9, -7, ...};

      __kernel void lookup(__global int* in, __global float* out){
          uint tid = get_global_id(0);
          out[tid] = (float)lookup_table[in[tid]];
      }

       

      My question: How costly are type casts? Would it be better to use type "float" for the lookup_table?