Plausibility
Some loop dependence relations can be parallelized (or vectorized) and some cannot. Each case must be analysed separately, but as a general rule of thumb, the following table cover most cases:
| ρ \ order | Lexically forward | Self-dependence | Lexically backward |
|---|---|---|---|
| positive (<) | plausible | plausible | plausible |
| zero (=) | implausible | δa: plausible
δf: implausible |
plausible |
| negative (>) | implausible | implausible | implausible |
Some implausible dependences can be transformed into plausible ones, for example, by means of re-arranging the statements.
Read more about this topic: Loop Dependence Analysis