Control Flow Graph Decision Node for Divergent Region Synchronization

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Control flow graphs with divergent conditions compromise parallelism during program code execution on processors, leading to inefficient execution due to divergent regions and runaway paths that hinder synchronization and optimization.

Innovation Solution

Identifying divergent regions of interest (DRIs) in control flow graphs and introducing a decision node to redirect and mark control flow paths, ensuring program thread synchronization and optimization by directing control flow to intended destinations based on markings.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If divergent conditions are present in control flow graph nodes, then program threads can handle different execution paths, but parallelism is compromised and execution efficiency decreases

Engineering Contradiction:

Improveprogram thread adaptabilityVSAvoidexecution efficiency

Core Design Contradiction:

Adaptability or versatilityVSProductivity

Solution Approach 1:

The control flow graph is segmented into divergent regions of interest (DRI) and non-divergent regions. By identifying and isolating divergent nodes, the patent segments the control flow to apply different optimization strategies to different regions, allowing parallel execution in non-divergent regions while handling divergence appropriately in marked regions.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Dominator nodes and post-dominator nodes serve as intermediaries to manage control flow divergence. These nodes act as synchronization points that coordinate between divergent and non-divergent regions, enabling parallel execution while maintaining correct program semantics across divergent paths.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If control flow paths diverge away from divergent regions, then alternative execution paths are enabled, but synchronization becomes difficult and runtime increases

Engineering Contradiction:

Improvecontrol flow flexibilityVSAvoidruntime

Core Design Contradiction:

Adaptability or versatilityVSLoss of time

Solution Approach 1:

The patent performs preliminary identification and marking of divergent regions and runaway paths during the compilation or analysis phase. By pre-marking these regions with metadata, the system prepares the control flow graph for optimized execution, allowing the runtime system to efficiently synchronize threads without ad-hoc analysis during execution.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The marking mechanism provides feedback information about control flow characteristics to the execution engine. By annotating runaway paths and divergent regions with metadata, the system enables the runtime system to make informed decisions about thread synchronization and parallelism optimization based on the marked control flow structure.

Inventive Principle:

Principle #23Feedback

3Productivity

If regular control flow paths are redirected to decision nodes, then control flow organization is improved and synchronization is enabled, but graph complexity increases

Engineering Contradiction:

Improveexecution efficiencyVSAvoidcontrol flow graph complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

Multiple control flow paths (both regular and runaway paths) are merged at dominator nodes and post-dominator nodes. This merging consolidates control flow convergence points, reducing the number of synchronization operations needed while maintaining correct program semantics across all divergent paths.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent adds a metadata dimension to the control flow graph by marking regions and paths with additional information. This dimensional extension allows the system to track and optimize control flow without fundamentally restructuring the graph, managing complexity through annotation rather than structural transformation.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Data Source

PatentUS9292269B2Control flow optimization for efficient program code execution on a processor

Publication Date: 2016.03.22 NVIDIA CORP

AI summary

A method includes identifying a divergent region of interest (DRI) not including a post dominator node thereof within a control flow graph, and introducing a decision node in the control flow graph such that the decision node post-dominates an entry point of the DRI and is dominated by the entry point. The method also includes redirecting a regular control flow path within the control flow graph from another node previously coupled to the DRI to the decision node, and redirecting a runaway path from the another node to the decision node. Further, the method includes marking the runaway path to differentiate the runaway path from the regular control flow path, and directing control flow from the decision node to an originally intended destination of each of the regular control flow path and the runaway path based on the marking to provide for program thread synchronization and optimization within the DRI.