  Semantic segmentation is pixel-wise classification which retains critical
spatial information. The "feature map reuse" has been commonly adopted in CNN
based approaches to take advantage of feature maps in the early layers for the
later spatial reconstruction. Along this direction, we go a step further by
proposing a fully dense neural network with an encoder-decoder structure that
we abbreviate as FDNet. For each stage in the decoder module, feature maps of
all the previous blocks are adaptively aggregated to feed-forward as input. On
the one hand, it reconstructs the spatial boundaries accurately. On the other
hand, it learns more efficiently with the more efficient gradient
backpropagation. In addition, we propose the boundary-aware loss function to
focus more attention on the pixels near the boundary, which boosts the "hard
examples" labeling. We have demonstrated the best performance of the FDNet on
the two benchmark datasets: PASCAL VOC 2012, NYUDv2 over previous works when
not considering training on other datasets.
