Performance Analysis

Running in parallel on 8 cores is 6× faster than on 1 core. What is the parallel efficiency?

  1. A75%
  2. B133%
  3. C48%
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Answer: A. 75%

Parallel efficiency is speedup divided by core count and indicates how effectively the cores are used. 6 ÷ 8 = 75%, three quarters of the ideal 8×. The remaining 25% is lost to synchronization waits, load imbalance, communication and contention for memory bandwidth. Efficiency tends to fall as cores are added, so the core count is chosen by how well efficiency holds up.

  • A. Correct. 6 ÷ 8 = 0.75.
  • B. That computes 8 ÷ 6.
  • C. That multiplies 6 by 8.
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  4. In software development, what is the purpose of automatically running benchmarks and recording results on every change?
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