Talk:Data dependency

From Wikipedia, the free encyclopedia

[edit] Off-topic?

This page is of topic as it discusses data hazards instead of data depencies. —Preceding unsigned comment added by 152.14.55.32 (talk)

No.. this does discuss data dependencies. You don't care about dependencies unless the dependency might cause problems on naive implimentations of data-paths - thus thats what this page discusses. Fresheneesz 01:00, 15 February 2007 (UTC)

[edit] WAW

Why is Write after Write a problem in any way? A better example is needed for this at least, because no compiler in their right mind would execute a write instruction if there were no read dependencies attached to the data that was written. Fresheneesz 01:00, 15 February 2007 (UTC)

I guess the data may be read later. If the order of these instructions was switched, the earlier value would be available, instead of the latter. So write-write-read sounds appropriate to me, but I am very unfamiliar with the topic and just speculating.

"because no compiler in their right mind would execute a write instruction if there were no read dependencies attached"

Data dependencies are not only relevant to compilers, but also the out-of-order execution units of a CPU; they cannot look ahead too far due to various constraints, so they do writes even if the values are never read (instruction-level parallelism) -- intgr 01:20, 15 February 2007 (UTC)

[edit] Φ?

 (I (S1) ∩ O(S2)) ∪ (O(S1) ∩ I(S2)) ∪ (O(S1) ∩ O(S2)) ≠ Φ

What is Φ? How do I have to understand the unions and intersections? --Abdull (talk) 17:00, 30 May 2008 (UTC)