When all of a vertex’s input channels become ready a new execution record is created for the vertex and placed in a scheduling queue. A disk-based channel is considered to be ready when the entire file is present. A channel that is a TCP pipe or shared-memory FIFO is ready when the predecessor vertex has at least one running execution record. A vertex and any of its channels may each specify a “hardconstraint” or a “preference” listing the set of computers on which it would like to run. The constraints are combined and attached to the execution record when it is added to the scheduling queue and they allow the application writer to require that a vertex be co-located with a large input file, and in general let the scheduler preferentially run computations close to their data.数据库中这些具体能做什么
时间: 2024-02-14 09:19:46 浏览: 24
这段文本描述了一个分布式计算系统中的调度和执行过程,其中包括了对输入通道的就绪状态判断、执行记录的创建和调度队列的管理,以及对计算节点的硬性约束和偏好设置等。如果将这个系统应用到数据库中,可以实现分布式计算和查询,提高计算效率和并发能力。具体来说,可以将数据库中的查询和计算任务分解成不同的子任务,分配到不同的计算节点上进行处理,通过就绪状态判断和调度队列的管理,实现任务的并发执行和优化调度。同时,可以通过硬性约束和偏好设置,将计算节点与数据节点相结合,实现数据本地化和计算本地化,从而进一步优化计算效率和响应速度。
相关问题
( c ) A directed multigraph with distinct vertices U ,...,U3 so that for each i , the vertex u , has in - degree i and out - degree i .
Sure, I understand your question. Here's a possible solution for the directed multigraph with the given properties:
We can create a directed multigraph with three vertices U1, U2, U3, such that each vertex has in-degree i and out-degree i for i in {1, 2, 3}. Here's how we can construct it:
- Start with three vertices U1, U2, U3.
- For each vertex Ui, add i outgoing edges to each of the other vertices, Uj ≠ Ui, for j in {1, 2, 3} and j ≠ i. This ensures that each vertex has out-degree i.
- For each vertex Ui, add i incoming edges from each of the other vertices, Uj ≠ Ui, for j in {1, 2, 3} and j ≠ i. This ensures that each vertex has in-degree i.
With this construction, we have a directed multigraph with three vertices, where each vertex has in-degree i and out-degree i for i in {1, 2, 3}.
Use Dijkstra's algorithm to find the shortest paths from vertex a to other vertices. In which order that the results must be obtained?
The order of the results obtained from using Dijkstra's algorithm to find the shortest paths from vertex a to other vertices is not specified by the algorithm itself. However, typically the results are obtained in ascending order based on the distance from vertex a to each of the other vertices.