Add reduction support in yaksa

[nusislam]

Pull Request Description

Expected Impact

Author Checklist

• Reference appropriate issues (with "Fixes" or "See" as appropriate)
• Commits are self-contained and do not do two things at once
• Commit message is of the form: module: short description and follows good practice
• Add comments such that someone without knowledge of the code could understand
• Have read and agree to the Yaksa CLA terms (https://github.com/pmodels/yaksa/wiki/Yaksa-Contributor-License-Agreement)