gistfile1.txt

        // get NE, NW, SE, SW pixel values from (x, y)
        int ix_nw = static_cast<int>(::floor(ix));
        int iy_nw = static_cast<int>(::floor(iy));
        int ix_ne = ix_nw + 1;
        int iy_ne = iy_nw;
        int ix_sw = ix_nw;
        int iy_sw = iy_nw + 1;
        int ix_se = ix_nw + 1;
        int iy_se = iy_nw + 1;
        
        // get surfaces to each neighbor:
        scalar_t nw = (ix_se - ix)    * (iy_se - iy);
        scalar_t ne = (ix    - ix_sw) * (iy_sw - iy);
        scalar_t sw = (ix_ne - ix)    * (iy    - iy_ne);
        scalar_t se = (ix    - ix_nw) * (iy    - iy_nw);
        
        // calculate bilinear weighted pixel value and set output pixel
        auto inp_ptr_NC = input.data + n * inp_sN;
        auto out_ptr_NCHW = output.data + n * out_sN + h * out_sH + w * out_sW;
        for (int c = 0; c < C; ++c, inp_ptr_NC += inp_sC, out_ptr_NCHW += out_sC) {
          *out_ptr_NCHW = static_cast<scalar_t>(0);
          if (within_bounds_2d(iy_nw, ix_nw, inp_H, inp_W)) {
            *out_ptr_NCHW += inp_ptr_NC[iy_nw * inp_sH + ix_nw * inp_sW] * nw;
          }
          if (within_bounds_2d(iy_ne, ix_ne, inp_H, inp_W)) {
            *out_ptr_NCHW += inp_ptr_NC[iy_ne * inp_sH + ix_ne * inp_sW] * ne;
          }
          if (within_bounds_2d(iy_sw, ix_sw, inp_H, inp_W)) {
            *out_ptr_NCHW += inp_ptr_NC[iy_sw * inp_sH + ix_sw * inp_sW] * sw;
          }
          if (within_bounds_2d(iy_se, ix_se, inp_H, inp_W)) {
            *out_ptr_NCHW += inp_ptr_NC[iy_se * inp_sH + ix_se * inp_sW] * se;
          }
        }