[High Performance Computing] {Udacity} L3: Intro to the Work-Span Model

https://s3.amazonaws.com/content.udacity-data.com/courses/gt-cse6220/Course+Notes/Lesson1-1+Introduction+(1).pdf

two parts:

1, task represented by DAG

edges << operations => better for parallelism

2, programming model defining DAG

work span analysis

https://maths-people.anu.edu.au/~brent/pub/pub022.html

second condition

brent‘s theorem:

https://crd-legacy.lbl.gov/~dhbailey/dhbpapers/twelve-ways.pdf

The correct answer depends on the situation.

The Holy Grail for span is to find a poly-logarithmic algorithm

replace par-for with a procedure call

for i loop, the y[i]s are independent from each other

but for j loop, every component depends on y[i]

eg

j loop is linear and executed by n times.

t[:] ← A[i,:] \cdot x[:]

linear work and logarithmic span (look at the forth slide of this page)

https://www.cprogramming.com/parallelism.html

原文地址：https://www.cnblogs.com/ecoflex/p/10888011.html