How to optimize algorithms? (parallel processing and/or faster algorithms). Provide examples for both

How to optimize algorithms? (parallel processing and/or faster algorithms). Provide examples for both



"Premature optimization is the root of all evil"; Donald Knuth

Parallel processing: for instance in R with a single machine.
- doParallel and foreach package
- doParallel: parallel backend, will select n-cores of the machine
- for each: assign tasks for each core
- using Hadoop on a single node
- using Hadoop on multi-node

Faster algorithm:
- In computer science: Pareto principle; 90% of the execution time is spent executing 10% of the code
- Data structure: affect performance
- Caching: avoid unnecessary work
- Improve source code level
For instance: on early C compilers, WHILE(something) was slower than FOR(;;), because WHILE evaluated "something" and then had a conditional jump which tested if it was true while FOR had unconditional jump.

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