[SYSTEMDS-1741] Rework codegen cost-based plan selector (opt V2)

• Type: Sub-task
• Status: Closed
• Priority: Major
• Resolution: Done
• Fix Version/s: SystemML 0.15
• Component/s: Compiler, Runtime
• Assignee: Matthias Boehm
• Reporter: Matthias Boehm
• Created: 30/Jun/17 06:31
• Updated: 09/Sep/17 03:35
• Resolved: 05/Aug/17 08:02

Description

So far our the cost-based codegen plan selector considers all materialization points per connected component of partial fusion plan candidates as well as multi aggregates and various cleanups in independent steps. This aims to rework this into a full-fledged cost-based optimizer to address poor plan choices encountered in various complex DAGs.

In detail, the new cost-based plan selector needs to address the following in an holistic manner:

• Potential materialization points (operators with multiple consumers), decided on a per-consumer basis
• Sparsity exploitation (in cost model and template flagging) incl ordering of inputs
• Decisions on (overlapping) template types
• Multi-aggregates for cell- and row-templates
• Constraints and costs for distributed operations (see SYSTEMML-1443)