 John D. McCalpin

John D. McCalpin developed STREAM, a benchmark for sustained memory bandwidth using simple operations on large arrays. His reference documentation specifies both execution rules and how the benchmark counts transferred bytes and arithmetic work, making reported rates interpretable.^[ref]

For the triad operation $a_i=b_i+s{c}_i$ on eight-byte values, the conventional accounting counts two reads and one write: 24 bytes per element, with two floating-point arithmetic operations. A measured rate of $24\mathrm{GB}{\mathrm{s}}^{-1}$ therefore corresponds to $10^9$ processed elements per second under that accounting. Actual memory-bus traffic can differ because of cache and write policies. The measurement targets data movement through a specified workload, rather than assuming that peak arithmetic throughput predicts application speed.