With the dependent relationship of tasks submitted by the users in the model of Cloud computing resources scheduling become stronger and stronger, it is worthy of studying how to optimize the scheduling strategy and algorithm to meet the different demands of the users, and it is absolutely importance. In this article, the author analysed the factors that will affect the entire task-sets execution firstly. Then proposed a new tasks scheduling model based on the original priority calculation method and the idea of redundant duplication of tasks. In the phase of tasks scheduling in the model, the execution results of all parent tasks of the subtask that being executing are considered. The costs of communication between task-sets has reduced by the method of redundant duplication of tasks, so that the execution time of some subtasks share be advanced, and the entire execution efficiency of task-sets can be increased. At the end of this article, from the comparative results of the space-time complexity of contrast algorithms and the algorithm proposed by the author during the process of processing dependent tasks, we can find that subtasks execution time can be advanced and the complete time of the whole task-set can be cut down to a certain extent
Dependent Tasks and the Resource Node ModellingThe dependent tasks are the tasks that in the task-sets submitted by users exist a certain dependent relationship between each other, and the relationship shows up in that before the subtask be executed, the execution results of its parent tasks must be known. And we can use a directed acyclic graph G to represent the dependent tasks [1]. As is shown in the following figure: The figure is represented as a four-tuples:, ,, , … , and | , ∈ , . The N represents the task node collection and the represents a single task node. The E represents the collection of "edge", and the edge determines the dependent relationship between tasks. If tow task nodes are connected by the edge, then there is a dependency relationship between them, and the sub task is the task node that the arrow points to, another side points to the parent task. The Q represents the average calculation cost collection for each task node, and the average calculation cost here refers to the average value of the cost of the task node in all resource nodes. The W represents the collection of communication cost between the tasks. And the special note here is that if tow dependencies are distributed to the same computing node, there is no communication cost between them [2].We can also make the following definition: Definition 1: pre v represents the predecessor task node set (or parent task node set) of the single task node v , and sub v represents the subsequent task node set (or sub task set) of the single task node v .Here we consider the computing node modelling next. Before that we need to do some declare first, the scheduling model of dependent tasks is consistent with the scheduling model of independent tasks, which has demonstrated in the