
2 Huixia Li et al.
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Fig. 1. The framework of our approach. The super-reso lu t io n opera ti o n is split into
three modules, i.e., low-level feature extractor, high-level fea t u re extractor and recon-
struction. We deploy PAMS with different α on each activation layer in the high-level
feature extractor. quant den o t es the quantization operation and clamp represents the
clamp function of quantization. Dash lines denote t h e weights are quantized with the
maximum. Here, we illustrate EDSR as backbone.
hot spot in computer vision for decades. Coming with the advances of dee p learn-
ing, deep convolutional neural networks (DCNNs) [ 7, 18, 23] have dominated SR
in recent years. These networks commonly use an extraction module to extract
a series of featur e maps from the LR image, cascaded with the u p- samp l in g
module, which stepwisely increases the resolution to reconstruct the HR image.
As one of the pioneering works for deep learning based SR, Dong et al. [7]
introduce three convolution layers to achieve high vis ual perception. After that,
Kim et al. [18] design a deep network VDSR by stacking 20 convolutional layers.
Subsequent works mainly resort to increasin g the network depth to improve SR
performance. For instance, Lim et al. [23] propose the enhanced deep resi d ual
networks (e.g. EDSR and MDSR) and remove batch normalization (BN) [16] to
reduce the memory consumption, which however still requires at least 64 convo-
lution layers (more than 160 layers for MDSR). A channel atte ntion mechanism
equipped into the RCAN model [38] requires more than 400 layers with about
30B FLOPs and 13M parameters. Such si gni fi cant computation and memory
overheads restrict their applications in scenarios where only limited memory
and computation resources are avai l abl e . Consequently, compressing deep SR
networks has attracted increasing attention recently [29].
Beyond SR, neural network compression and acceleration have been widely
studied in the literature. Representative works include parameter pruning [11–13,
27, 26, 22], low-rank approximation [6, 24, 25], compact networks [33, 28], knowl-
edge distillat ion (KD) [14, 32], neural architecture search (NAS) [43, 40] and
quantization [5, 17]. Considering the uniq ue structures such as EDSR [23] and
RDN [39] in SR, it is by nature t o leverage quantization schemes to acceler-
ate and compress SR networks, i.e., by converting full-precision weights [17],
activations [2], and gradients [41] to low bits.
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