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The pattern "ALU saturation" describes the performance limitation caused by fully utilizing a functional unit inside a CPU core.


  • Throughput at design limit(s)
  • Good (low) CPI
  • Integral ratio of cycles to specific instruction count(s).


Use a hardware-counter tool like:

  • LIKWID with performance groups FLOPS_SP, FLOPS_DP, DATA and CLOCK
  • Same information can be provided by perf or PAPI

Possible optimizations and/or fixes