code: def im2col_gpu(
      img,
      kh,
      kw,
      sy,
      sx,
      ph,
      pw,
      cover_all=False,
      dy=1,
      dx=1,
      out_h=None,
      out_w=None,
  ):
      n, c, h, w = img.shape
      if out_h is None:
          out_h = get_conv_outsize(h, kh, sy, ph, cover_all, dy)
      assert out_h > 0, "Height in the output should be positive."
      if out_w is None:
          out_w = get_conv_outsize(w, kw, sx, pw, cover_all, dx)
      assert out_w > 0, "Width in the output should be positive."
  
      col = cuda.cupy.empty(
          (n, c, kh, kw, out_h, out_w), dtype=img.dtype
      )
      cuda.elementwise(
          "raw T img, int32 h, int32 w, int32 out_h, int32 out_w,"
          "int32 kh, int32 kw, int32 sy, int32 sx, int32 ph, int32 pw,"
          "int32 dy, int32 dx",
          "T col",
          """
             int c0 = i / (kh * kw * out_h * out_w);
             int ky = i / (kw * out_h * out_w) % kh;
             int kx = i / (out_h * out_w) % kw;
             int out_y = i / out_w % out_h;
             int out_x = i % out_w;
             int in_y = ky * dy + out_y * sy - ph;
             int in_x = kx * dx + out_x * sx - pw;
             if (in_y >= 0 && in_y < h && in_x >= 0 && in_x < w) {
               col = img[in_x + w * (in_y + h * c0)];
             } else {
               col = 0;
             }
          """,
          "im2col",
      )(
          img.reduced_view(),
          h,
          w,
          out_h,
          out_w,
          kh,
          kw,
          sy,
          sx,
          ph,
          pw,
          dy,
          dx,
          col,
      )
      return col
  
file_path: chainer/chainer/utils/conv.py
imports: import numpy
  import six
  from chainer.backends import cuda
label_desc: Use image node_id 4 for calling a global function with example usage: im2col_gpu(img, kh, kw, sy, sx, ph, pw, cover_all, dy, dx, out_h, out_w) and returns: col