Why is Apache-Spark - Python so slow locally as compared to pandas?
Because:
- Apache Spark is a complex framework designed to distribute processing across hundreds of nodes, while ensuring correctness and fault tolerance. Each of these properties has significant cost.
- Because purely in-memory in-core processing (Pandas) is orders of magnitude faster than disk and network (even local) I/O (Spark).
- Because parallelism (and distributed processing) add significant overhead, and even with optimal (embarrassingly parallel workload) does not guarantee any performance improvements.
- Because local mode is not designed for performance. It is used for testing.
- Last but not least - 2 cores running on 393MB is not enough to see any performance improvements, and single node doesn't provide any opportunity for distribution
- Also Spark: Inconsistent performance number in scaling number of cores, Why is pyspark so much slower in finding the max of a column?, Why does my Spark run slower than pure Python? Performance comparison
You can go on like this for a long time...