Memory Constrained Scaling
Scale so memory usage per processor stays fixed
Scaled Speedup: Time(1) / Time(p) for scaled up problem
- Hard to measure Time(1), and inappropriate
SpeedupMC(p) =
Can lead to large increases in execution time
- If work grows faster than linearly in memory usage
- e.g. matrix factorization
- 10,000-by 10,000 matrix takes 800MB and 1 hour on uniprocessor. With 1,000 processors, can run 320K-by-320K matrix, but ideal parallel time grows to 32 hours!
- With 10,000 processors, 100 hours ...