Search results
Results from the WOW.Com Content Network
In the example below, there is an output dependency between instructions 3 and 1 — changing the ordering of instructions in this example will change the final value of A, thus these instructions cannot be executed in parallel. 1. B = 3 2. A = B + 1 3. B = 7 As with anti-dependencies, output dependencies are name dependencies. That is, they ...
A statement S2 is output dependent on S1 (written ) if and only if S1 and S2 modify the same resource and S1 precedes S2 in execution. The following is an example of an output dependence (WAW: Write After Write): S1 x := 10 S2 x := 20 Here, S2 and S1 both set the variable x.
In this example, there is an output dependence between statements S1 and S2. Here, the variable c is first written to in S1 and then variable c is written to again in statement S2. This output dependence can be represented by S1 →O S2. An output dependence can be seen by different iterations in a loop.
There are several main solutions and algorithms used to resolve data hazards: insert a pipeline bubble whenever a read after write (RAW) dependency is encountered, guaranteed to increase latency, or; use out-of-order execution to potentially prevent the need for pipeline bubbles; use operand forwarding to use data from later stages in the pipeline
To make sure we respect the three types of dependencies, we construct a dependency graph, which is a directed graph where each vertex is an instruction and there is an edge from I 1 to I 2 if I 1 must come before I 2 due to a dependency. If loop-carried dependencies are left out, the dependency graph is a directed acyclic graph.
Database normalization is the process of structuring a relational database in accordance with a series of so-called normal forms in order to reduce data redundancy and improve data integrity. It was first proposed by British computer scientist Edgar F. Codd as part of his relational model .
In relational database theory, an embedded dependency (ED) is a certain kind of constraint on a relational database. It is the most general type of constraint used in practice, including both tuple-generating dependencies and equality-generating dependencies. Embedded dependencies can express functional dependencies, join dependencies ...
The chase is a simple fixed-point algorithm testing and enforcing implication of data dependencies in database systems. It plays important roles in database theory as well as in practice. It is used, directly or indirectly, on an everyday basis by people who design databases, and it is used in commercial systems to reason about the consistency ...