Impact of Intel Compiler Optimizations on SPEC CPU2017 Example
After publishing the Over 2000 SPEC CPU 2017 Results Flagged for Compiler Optimization piece yesterday, we have more details to share and a good example of the impacts. As a result, we thought we would share a quick follow-up piece.
Just for some context, while we said in our original piece that it is “over 2000” results, it appears as though it is over 2500 results that are impacted. These results have the following note added to them:
SPEC has ruled that the compiler used for this result was performing a compilation that specifically improves the performance of the 523.xalancbmk_r / 623.xalancbmk_s benchmarks using a priori knowledge of the SPEC code and dataset to perform a transformation that has narrow applicability.
In order to encourage optimizations that have wide applicability (see rule 1.4 https://www.spec.org/cpu2017/Docs/runrules.html#rule_1.4), SPEC will no longer publish results using this optimization.
The SPEC CPU2017 integer rate 523.xalancbmk_r and speed 623.xalancbmk_s benchmarks were found to be impacted by a specific optimization in the Intel compiler. It seems as though these optimizations were in the 2022 version of the compiler, but the latest 2023.2.3 version that was generally used for the latest 5th Gen Intel Xeon “Emerald Rapids” launch no longer had the optimizations. Given 2022-2023 timeframes, most of the impacted results seem to be 4th Gen Intel Xeon “Sapphire Rapids” results.
