Eager mode is easier to use, more suitable for ML researchers, and hence is the default mode of execution
PyTorch executes operations line-by-line without a wholistic view of the code. It has the benefit of flexibility and easier to debug at the cost of many optimization opportunities.

github.com
https://github.com/kimbochen/md-blogs/tree/main/pytorch-systems-intro
Optimizing Production PyTorch Models’ Performance with Graph Transformations
1. Introduction
https://pytorch.org/blog/optimizing-production-pytorch-performance-with-graph-transformations/

Seonglae Cho