rattio

Rattio is a term used in parallel computing and distributed computing to describe the ratio of the actual computing power to the theoretical maximum computing power. It is also known as computation-to-communication (C2C) ratio or bandwidth to computation (B/C) ratio. This concept is essential in understanding the performance of different parallel computers and identifying the bottlenecks in the system.

The term "rattio" is believed to have originated from NASA's Scalable Adaptive Compression Algorithm (SACA) project in the 1990s. Researchers there used it to describe the ratio of actual computer power to the maximum theoretical computing power. Later, the term gained wider acceptance in the field of high-performance computing.

Rattio is an important metric in evaluating the performance of parallel computing platforms, clusters, and grids. It provides insights into how efficiently a system can utilize its resources, such as processors, memory, and communication links. A high rattio indicates efficient utilization of resources and thus better performance, while a low rattio may indicate a bottleneck that limits the system's overall performance.

Rattio can be calculated in several ways, depending on the target architecture and the specific performance characteristics of interest. The most common approach involves dividing the system's peak floating-point operations per second (FLOPS) by the actual FLOPS achieved, taking into account memory access patterns, memory hierarchy, and communication overhead. The resulting value provides a numerical estimate of the rattio, enabling performance engineers and researchers to compare and contrast different systems and identify opportunities for improvement.