opencv/modules/dnn/src/opencl/ocl4dnn_lrn.cl

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#define CONCAT(A,B) A##_##B
#define TEMPLATE(name,type) CONCAT(name,type)
#define KERNEL_ARG_DTYPE float

#if defined(cl_khr_fp16)
#pragma OPENCL EXTENSION cl_khr_fp16 : enable
#endif

__kernel void TEMPLATE(lrn_full_no_scale,Dtype)(const int nthreads, __global const Dtype* in,
                             const int num, const int channels,
                             const int height, const int width, const int size,
                             const KERNEL_ARG_DTYPE alpha_over_size, const KERNEL_ARG_DTYPE k,
                             __global Dtype* const out,
                             const KERNEL_ARG_DTYPE negative_beta) {
  for (int index = get_global_id(0); index < nthreads;
      index += get_global_size(0)) {
    // find out the local offset
    const int w = index % width;
    const int h = (index / width) % height;
    const int n = index / width / height;
    const int offset = (n * channels * height + h) * width + w;
    const int step = height * width;
    __global const Dtype* in_off = in + offset;
    __global Dtype* out_off = out + offset;
    int head = 0;
    const int pre_pad = (size - 1) / 2;
    const int post_pad = size - pre_pad - 1;
    float accum_scale = 0;
    // fill the scale at [n, :, h, w]
    // accumulate values
    while (head < post_pad && head < channels) {
      float v = in_off[head * step];
      accum_scale += v * v;
      ++head;
    }
    // both add and subtract
    while (head < channels) {
      float v = in_off[head * step];
      accum_scale += v * v;
      if (head - size >= 0) {
        v = in_off[(head - size) * step];
        accum_scale -= v * v;
      }
      float scale_val = k + accum_scale * alpha_over_size;
      out_off[(head - post_pad) * step] = (Dtype)((float)in_off[(head - post_pad) * step] * native_powr(scale_val, negative_beta));
      ++head;
    }
    // subtract only
    while (head < channels + post_pad) {
      if (head - size >= 0) {
        float v = in_off[(head - size) * step];
        accum_scale -= v * v;
      }
      float scale_val = k + accum_scale * alpha_over_size;
      out_off[(head - post_pad) * step] = (Dtype)((float)in_off[(head - post_pad) * step] * native_powr(scale_val, negative_beta));
      ++head;
    }
  }
}