Optimizer

Executable

discopop_optimizer

The optimizer is experimental. It is not part of the GUI or MCP server pipeline; both use the autotuner to select suggestions.

Purpose

• Build an optimization graph from the program execution graph and the patterns found by the explorer, and evaluate mappings of the patterns to the devices described in a system configuration.
• Identify loop nests that can be collapsed (the collapse clause of loops).
• Select a combination of multiple patterns (-o: greedy, evolutionary or exhaustive search) so you do not have to choose combinable patterns manually.

Required input

Run the tool from inside the .discopop directory.

• File mapping
• Profiling and instrumentation output
• explorer/patterns.json, created by the explorer

Optional input

• Overhead measurements of the target system obtained with the OpenMP microbenchmark suite (OpenMP-Microbench), passed with --doall-microbench-file and --reduction-microbench-file.
• A system configuration file (optimizer/system_configuration.json by default). The optimizer creates a default one if the file does not exist.

Output

The optimizer extends the original set of patterns with its results and stores them in optimizer/patterns.json (inside .discopop), next to the experiment data of the run.

The patch generator does not read this file by default. To create patches for it, run:

discopop_patch_generator -a optimizer/patterns.json

Options

Option	Default	Description
-v, --verbose	off	Enable verbose output.
-p	0	Program path pruning: 0 none, 1 prune to the paths that cover 80% of the observed decisions per path split, 2 prune to the most likely path.
-o	0	Optimization level: 0 none, 1 greedy, 2 evolutionary, 3 exhaustive.
-opt-2-params <population_size> <generations>	50 5	Parameters of the evolutionary optimization (-o 2).
-s, --single-suggestions	off	Generate individual suggestions for device mappings.
--doall-microbench-file	none	Do-all microbenchmark results.
--reduction-microbench-file	none	Reduction microbenchmark results.
--system-configuration	optimizer/system_configuration.json	System configuration file.
--pin-function-calls-to-host	off	Force function calls on the host; prevents offloading of entire functions.
--profiling	off	Profile the optimizer (writes optimizer_profile.txt).
--log	WARNING	Log level.
--write-log	off	Write a log file.

Interactive pattern merging:

Option	Description
-i, --interactive	Start the interactive pattern merge tool.
--interactive-export <ids>	Merge and export the comma-separated suggestion ids. Requires -i.

Experimental options:

Option	Description
--allow-nested-parallelism	Allow nested parallelism suggestions. The cost estimation may be inaccurate.
--check-called-function-for-nested-parallelism	Extend the nesting check to called functions. Can increase the run time significantly.
--plot	Plot the internal graph.