float im2col_get_pixel(__global float *im, int height, int width, int channels,
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int batch, int row, int col, int channel, int pad)
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{
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row -= pad;
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col -= pad;
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if (row < 0 || col < 0 || row >= height || col >= width) return 0;
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int index = col + width*(row + height*(channel+batch*channels));
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return im[index];
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}
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__kernel void im2col(__global float *data_im, int batch,
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int channels, int height, int width,
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int ksize, int stride, int pad, __global float *data_col)
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{
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int c,h,w,b;
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int height_col = (height - ksize) / stride + 1;
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int width_col = (width - ksize) / stride + 1;
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int channels_col = channels * ksize * ksize;
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if (pad){
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height_col = 1 + (height-1) / stride;
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width_col = 1 + (width-1) / stride;
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pad = ksize/2;
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}
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int id = get_global_id(0);
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w = id % width_col;
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id /= width_col;
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h = id % height_col;
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id /= height_col;
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c = id % channels_col;
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id /= channels_col;
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b = id % batch;
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id /= batch;
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int col_size = height_col*width_col*channels_col;
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int w_offset = c % ksize;
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int h_offset = (c / ksize) % ksize;
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int c_im = c / ksize / ksize;
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int im_row = h_offset + h * stride;
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int im_col = w_offset + w * stride;
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int col_index = (c * height_col + h) * width_col + w + b*col_size;
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data_col[col_index] = im2col_get_pixel(data_im, height, width, channels, b, im_row, im_col, c_im, pad);
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}
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