Communicate or coordinate or perhaps no signicant need

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: ess significant terms! •  In this class, we’ll mainly be concerned with primary effects (asymptotic analysis)! •  In the real world, secondary effects are also often worth paying attention to (after the primary ones)! UW, Autumn 1999! CSE 373 – Data Structures and Algorithms! Brad Chamberlain! “Returning to the present...” In Parallel Compu3ng, Constants Maher •  AsymptoEc analysis (big- O notaEon) is crucial in parallel compuEng, as in tradiEonal compuEng •  However, constant factors also maber –  in parEcular, we’ll be running on a constant number of processors •  anecdote from computaEonal chemist colleague –  also, since performance is a primary moEvator for parallel compuEng, we typically want to squeeze out as many overheads as possible CSEP 524: Parallel ComputaEon Winter 2013: Chamberlain 53 Measuring Parallel Computa3ons (Directly) Timings: How long did the program take to run? –  typically measured in wallclock seconds (or fracEons thereof) Performance: At what rate is the program running? –  e.g., FLOPS (floaEng point operaEons per second) •  or simply OPS –  or something more domain- specific: •  graph codes: TEPS (traversed edges per second) •  memory bandwidth: GB/s (gigabytes per second) •  table updates: GUPS (giga- updates per second) CSEP 524: Parallel ComputaEon Winter 2013: Chamberlain 54 Measuring Parallel Computa3ons (Rela3vely) Speedup: How does the parallel execuEon compare to a serial execuEon? Speedupp = Tserial / Tp Linear/Ideal Speedup: Speedupp = p CSEP 524: Parallel ComputaEon Winter 2013: Chamberlain 55 Sample Speedup Graph CSEP 524: Parallel ComputaEon Winter 2013: Chamberlain 56 Compu3ng Speedup: The Baseline A key issue: What to use for the serial Eming? –  some opEons: •  the parallel code running using 1 task/processor? •  a serial implementaEon of the same algorithm? •  the best serial implementaEon available? –  The last is the most ideal/valuable •  e.g., if...
View Full Document

Ask a homework question - tutors are online