Abstract
Multidirected acyclic graph (DAG) workflow scheduling is a key problem in the heterogeneous distributed environment in the distributed computing field. A hierarchical heterogeneous multi-DAG workflow problem (HHMDP) was proposed based on the different signal processing workflows produced by different grouping and scanning modes and their hierarchical processing in specific functional signal processing modules in a multigroup scan ultrasonic phased array (UPA) system. A heterogeneous predecessor earliest finish time (HPEFT) algorithm with predecessor pointer adjustment was proposed based on the improved heterogeneous earliest finish time (HEFT) algorithm. The experimental results denote that HPEFT reduces the makespan, ratio of the idle time slot (RITS), and missed deadline rate (MDR) by 3.87–57.68%, 0–6.53%, and 13–58%, respectively, and increases relative relaxation with respect to the deadline (RLD) by 2.27–8.58%, improving the frame rate and resource utilization and reducing the probability of exceeding the real-time period. The multigroup UPA instrument architecture in multi-DAG signal processing flow was also provided. By simulating and verifying the scheduling algorithm, the architecture and the HPEFT algorithm is proved to coordinate the order of each group of signal processing tasks for improving the instrument performance.
Highlights
Ultrasonic phased array (UPA) systems with a large number of elements can achieve multigroup scanning, increase the scanning flexibility, and enhance the resolution and contrast of the resulting images
The priority constraints related to the multigroup tasks combine with the functional constraints on shared resources to form a hierarchical heterogeneous multi-directed acyclic graph (DAG) workflow problem (HHMDP)
This study uses the critical path method by considering the hierarchical and specified function constraints of the shared resources to propose an improved method for heterogeneous earliest finish time (HEFT) that incorporates predecessor pointer adjustment (PPA), which can be referred to as the heterogeneous predecessor earliest finish time (HPEFT)
Summary
Ultrasonic phased array (UPA) systems with a large number of elements can achieve multigroup scanning, increase the scanning flexibility, and enhance the resolution and contrast of the resulting images. This study uses the critical path method by considering the hierarchical and specified function constraints of the shared resources to propose an improved method for HEFT that incorporates predecessor pointer adjustment (PPA), which can be referred to as the heterogeneous predecessor earliest finish time (HPEFT) This method can coordinate the different signal processing steps to satisfy the priority constraints represented by the multi-DAG model under the multigroup scanning architecture of a UPA system with multiple layers and shared resources for performing the specified functions. This coordination reduces the maximum completion time (makespan) and improves the utilization rate of the shared resources, improving the real-time frame rate and reducing the energy consumption.
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