ENAF: A Multi-Exit Network with an Adaptive Patch Fusion for Large Image Super Resolution

To accelerate single image super-resolution (SISR) networks on large images (2K-8K) many recent approaches decompose an image into small patches and dynamically determine an execution path according to its difficulty (referred to as a dynamic network). To quantify the hardness of a patch they mainly rely on a handcrafted assessment score e.g. edge which weakly associates a patch's texture with the computational complexity of a SISR model. To address the problem we introduce ENAF - a dynamic network for SISR with an adaptive patch fusion. Built on top of a backbone ENAF incorporates multiple early exits (EEs) to tackle the over-parameterized SISR model. More importantly ENAF plugs a tiny network that estimates PSNR to associate data texture with a computation cost at an EE. Based on the scores ENAF effectively assigns image patches to an exit enhancing the quality-complexity trade-off. Extensive experiments on common datasets with popular SISR backbones demonstrate the effectiveness of ENAF in various settings. The source code will be available.