Vector Gather Circuitry with Narrow Datapath and Dynamic Buffering
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Solution Overview
Problem
Vector gather instructions face challenges in achieving high performance in temporal vector processors due to the lack of simultaneous availability of operands, leading to difficulties in gathering multiple elements per cycle, especially when indices refer to non-adjacent data elements, requiring multiple register-file accesses.
Innovation Solution
Implementing a vector gather mechanism that opportunistically processes multiple indices per cycle by reading nearby indices and data elements, using a completion flags buffer to track processed indices, and exploiting small vector cases to simplify processing and reduce power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If vector gather instructions are implemented in temporal vector processors, then the ability to process vector operations is improved, but the performance is degraded due to lack of simultaneous operand availability and multiple register-file accesses
Solution Approach 1:
The patent applies preliminary action by predicting which data elements will be needed based on the index register values before actual execution. The system pre-loads data into operand buffers in advance, so that when the vector gather instruction executes, the data is already available, eliminating the performance bottleneck of multiple sequential register-file accesses.
Solution Approach 2:
The patent transitions from a narrow datapath that processes one element at a time to a wider datapath that can process multiple data elements simultaneously. By expanding the datapath width to match the buffer capacity, the system gathers multiple elements per cycle, effectively adding a parallelism dimension to the execution model.
2Productivity
If multiple indices are processed per cycle, then execution efficiency is improved, but the datapath width must be increased which increases device complexity
Solution Approach 1:
The patent implements dynamic operand buffering where the buffer width and processing capacity are adapted based on the specific vector operation being executed. The system can dynamically adjust between processing 1, 2, 4, or 8 elements per cycle depending on the vector length and operation requirements, optimizing performance without permanently requiring the maximum datapath width for all operations.
Solution Approach 2:
The patent changes the datapath width parameter dynamically based on the vector operation being performed. By using configurable buffer widths and selective activation of processing lanes, the system can widen the datapath only when needed for specific operations, maintaining narrow datapath benefits for other operations while still achieving high throughput when required.
3Reliability
If completion tracking is implemented for all indices, then execution accuracy is improved, but power consumption increases
Solution Approach 1:
The patent extracts and tracks only the completion status of relevant indices rather than all indices. By identifying which indices actually require data gathering and tracking only those, the system maintains execution accuracy while reducing the overhead of completion tracking logic and associated power consumption for indices that don't require processing.
Data Source
AI summary
Systems and methods are disclosed for vector gather with a narrow datapath. For example, some methods may include reading b bits of a vector of indices into a first operand buffer; reading b bits of the vector of source data into a second operand buffer, including an element indexed by a first index stored in the first operand buffer; checking whether other indices stored in the first operand buffer point to elements of the vector of source data stored in the second operand buffer; during a single clock cycle, copying a plurality of elements stored in the second operand buffer that are pointed to by indices stored in the first operand buffer to a third operand buffer; and updating flags in a completion flags buffer corresponding to those indices to indicate that handling of those indices has completed.