The AWS Deep Learning AMIs now include advanced optimizations for Chainer 4 and Microsoft Cognitive Toolkit (CNTK) 2.5.1 that are tailored to deliver higher-performance training across Amazon EC2 instances.  

Source: Amazon Web Services News AWS Deep Learning AMIs Now Include Optimized Chainer 4 and CNTK 2.5.1 to Accelerate Deep Learning on Amazon EC2 Instances