Compiler Control Word Tags for Parallel Memory Hazard Mitigation
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Solution Overview
Problem
Existing parallel processing architectures face challenges in efficiently mitigating memory access hazards such as write-after-read, read-after-write, and write-after-write conflicts, leading to inefficiencies in data processing and increased costs due to ineffective data handling.
Innovation Solution
The implementation of a control word tag system, where a compiler-generated control word tag supports memory access precedence information, enabling hazardless memory access operations by determining the order of memory access operations and modifying tags during runtime to accommodate changing memory access hazards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If memory access operations are executed in parallel without hazard mitigation, then processing speed is improved, but data correctness deteriorates due to write-after-read, read-after-write, and write-after-write conflicts
Solution Approach 1:
The compiler performs preliminary analysis at compile time to identify and tag memory access operations that may have hazards. Control word tags are generated in advance to mark operations requiring hazard mitigation, allowing the hardware to execute these operations in a safe sequential manner without stalling other parallel operations.
Solution Approach 2:
Control word tags act as intermediaries between the compiler's hazard analysis and the hardware's execution control. The tags carry precedence information that mediates the interaction between parallel memory access operations, enabling the hardware to automatically resolve potential conflicts without complex runtime hazard detection logic.
2Reliability
If hazard mitigation is implemented through runtime checking and stalling, then data correctness is improved, but processing speed deteriorates due to execution stalls
Solution Approach 1:
Instead of performing hazard checking at runtime, the compiler performs the hazard analysis and generates appropriate control word tags at compile time. This preliminary action eliminates the need for runtime stalling, as the hardware can simply follow the pre-determined execution order indicated by the tags.
Solution Approach 2:
The patent replaces the mechanical runtime hazard detection and stalling mechanism with a compiler-driven tagging system. The complex runtime checking logic is substituted with simple hardware that executes operations based on pre-computed tags, significantly reducing execution overhead.
3Reliability
If control word tags with precedence information are used, then hazard mitigation is improved, but device complexity increases due to tag generation and processing
Solution Approach 1:
The control word tag serves as a lightweight intermediary structure that carries only the essential precedence information needed for hazard mitigation. This simple tagged structure enables complex hazard management without requiring substantial changes to the underlying hardware architecture.
Solution Approach 2:
The patent modifies the control word format by adding tags with precedence information, changing the parameter structure of memory access operations. This parameter change allows the system to encode hazard mitigation requirements directly in the control words, eliminating the need for separate hazard detection hardware.
4Reliability
If memory access operations are executed sequentially to avoid hazards, then data correctness is improved, but productivity deteriorates due to reduced parallelism
Solution Approach 1:
The compiler performs preliminary hazard analysis and generates control word tags that identify which operations require sequential execution. This allows the system to maintain sequential execution only where necessary while preserving parallel execution for operations that do not have hazards, optimizing the balance between correctness and throughput.
Solution Approach 2:
Instead of sequentially executing all memory access operations, the system applies sequential execution selectively only to operations tagged with hazard information. This partial application of sequential execution maintains data correctness while preserving parallelism for the majority of operations that do not require hazard mitigation.
Data Source
AI summary
Techniques for parallel processing based on hazard mitigation avoidance are disclosed. An array of compute elements is accessed. Each compute element within the array is known to a compiler and is coupled to its neighboring compute elements within the array of compute elements. Control for the compute elements is provided on a cycle-by-cycle basis. Control is enabled by a stream of wide control words generated by the compiler. Memory access operation hazard mitigation is enabled. The hazard mitigation is enabled by a control word tag. The control word tag supports memory access precedence information and is provided by the compiler at compile time. A hazardless memory access operation is executed. The hazardless memory access operation is determined by the compiler, and the hazardless memory access operation is designated by a unique set of precedence information contained in the tag. The tag is modified during runtime by hardware.