Processor Gather Scatter Exception Handling
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Solution Overview
Problem
SIMD architectures face inefficiencies in applications with irregular memory access patterns, particularly due to the overhead of rearranging data elements stored in non-contiguous memory locations, which limits the utilization of SIMD hardware as vector widths increase.
Innovation Solution
Implementing a processor device that decodes a single instruction for data transfer between storage locations, issues the instruction for execution, detects exceptions, and delivers pending traps or interrupts to an exception handler before delivering the exception, allowing for efficient gather and scatter operations by saving the state of the operation and resuming from the interruption point.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If data elements are stored in non-contiguous memory locations to support irregular memory access patterns, then application flexibility is improved, but SIMD hardware utilization deteriorates due to rearrangement overhead
Solution Approach 1:
The patent divides the data transfer operation into multiple segments by processing data elements in batches rather than all at once. When an exception occurs, only the current batch needs to be redone rather than the entire operation, reducing the penalty while maintaining support for non-contiguous memory access patterns through gather/scatter operations
Solution Approach 2:
The patent performs preliminary actions by saving the state of completed data elements before an exception occurs. This allows the system to resume from the interruption point without redoing work on already-processed elements, thereby maintaining high SIMD utilization while handling irregular memory access patterns
2Power
If vector width is increased to improve SIMD performance, then processing capability is improved, but rearrangement overhead increases making full utilization more difficult
Solution Approach 1:
The patent segments large vector operations into smaller manageable batches. This reduces the complexity of data rearrangement for wide vectors by breaking them into smaller chunks that can be handled more efficiently, while still utilizing the full processing capability of wide SIMD units
Solution Approach 2:
The patent applies partial action by processing subsets of data elements in each batch rather than attempting to process the entire vector at once. This reduces the immediate rearrangement complexity while maintaining overall processing power through multiple passes
3Reliability
If gather and scatter operations are interrupted by exceptions, then exception handling is necessary, but operation overhead increases when progress is discarded and operations must restart
Solution Approach 1:
The patent performs preliminary state saving during interrupted gather/scatter operations. By recording which data elements have been successfully processed before an exception occurs, the system can resume from the interruption point without redoing work, maintaining reliability while minimizing time loss
Solution Approach 2:
The patent ensures continuity of useful action by resuming interrupted operations from the point of interruption rather than restarting from the beginning. This maintains the continuous processing of data elements while properly handling exceptions, reducing overhead and preserving progress
Data Source
AI summary
According to a first aspect, efficient data transfer operations can be achieved by: decoding by a processor device, a single instruction specifying a transfer operation for a plurality of data elements between a first storage location and a second storage location; issuing the single instruction for execution by an execution unit in the processor; detecting an occurrence of an exception during execution of the single instruction; and in response to the exception, delivering pending traps or interrupts to an exception handler prior to delivering the exception.