Collective Message Aggregation for Low-Latency HPC Data Exchange
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Solution Overview
Problem
Existing collective communication protocols in high-performance computing (HPC) suffer from inefficiencies due to uncertainty in message sizes, leading to bottlenecks and increased communication load and latency, particularly in operations like all-to-all-v and all-to-all-w, where processes exchange data without advance information about message sizes.
Innovation Solution
A method and system for collective communications that compose messages with metadata indicating how data are to be handled by destination processes, allowing concurrent transmission of both metadata and data in a single operation, with selective data transmission and aggregation based on predefined thresholds, using techniques like RDMA for large data transfers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If each member process transmits messages to all other member processes in large-scale HPC distributed applications, then complete data exchange is achieved, but communication burden and latency increase significantly
Solution Approach 1:
The patent combines multiple individual messages into a single aggregated message that is transmitted once to all destination processes. Instead of each source process sending separate messages to all destinations, the system aggregates data from multiple sources into one message per destination, reducing the total number of transmissions and lowering communication latency while maintaining complete data exchange.
Solution Approach 2:
The patent performs preliminary aggregation of messages at source processes before transmission. By pre-combining messages that will be sent to the same destination, the system prepares aggregated messages in advance, reducing the communication burden during the actual data exchange phase and minimizing latency.
2Productivity
If message aggregation protocols are used to reduce communication burden, then communication overhead is reduced, but complexity in message composition and handling increases
Solution Approach 1:
The patent segments the message handling process into distinct phases: aggregation at source processes, transmission of aggregated messages, and disaggregation at destination processes. This segmentation allows each process to perform a simplified, specialized function rather than handling the complete complex operation, reducing individual process complexity while maintaining overall efficiency.
Solution Approach 2:
The patent introduces an intermediary aggregation mechanism that sits between individual message sources and destinations. The aggregation layer combines messages from multiple sources into unified messages for each destination, simplifying the communication model by providing a clear intermediate step that manages complexity centrally rather than at each endpoint.
3Ease of operation
If metadata is included in messages to indicate data handling instructions, then destination processes can efficiently handle data, but message size and transmission overhead increase
Solution Approach 1:
The patent extracts handling instructions into separate metadata fields that are attached to aggregated messages rather than embedding detailed instructions within each individual data transmission. This extraction allows destination processes to efficiently interpret handling requirements while keeping the actual data payload separate and optimized for transmission.
Data Source
AI summary
A method for collective communications includes invoking a collective operation over a group of computing processes in which the processes concurrently transmit and receive data to and from other processes in the group via a communication medium. Messages are composed for transmission by source processes including metadata indicating how the data to be transmitted by the source processes in the collective operation are to be handled by destination processes that are to receive the data and also including in at least some of the messages the data to be transmitted by one or more of the source processes to one or more of the destination processes. The composed messages are transmitted concurrently from the source processes to the destination processes in the group over the communication medium. The data are processed by the destination processes in response to the metadata included in the messages received by the destination processes.