Browsing by Author "Chang, RI"

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A new real-time disk scheduling algorithm and its application to distributed multimedia storage systems
(1998)
Chang, RI
;
Shih, WK
;
Chang, RC
;
資訊工程學系
;
Department of Computer Science
In this paper, a new real-time disk scheduling algorithm called BFI (best-fit-insertion) is proposed. Notably, different from the conventional realtime problem, the service time of a disk request depends on its schedule result. As the service time is not a constant value, it is time-consuming to verify the feasibility of a schedule. In this paper, we introduce a temporal parameter called maximum tardiness. With the help of maximum tardiness, we can verify the improvement of an insertion test within a constant time. We have evaluated and implemented our proposed algorithm on operating systems. Experiments show that the proposed algorithm can support more requests and can achieve higher disk throughput than that of the conventional approach.
Cache-aware real-time disk scheduling
(2004-09-01)
Chang, HP
;
Chang, RI
;
Shih, WK
;
Chang, RC
;
資訊工程學系
Previous real-time disk scheduling algorithms assume that each disk request incurs a physical disk mechanical operation and only consider how to move the disk head under real-time constraints. However, with the increased capacity of on-disk cache, modern disk drives read-ahead data aggressively. Thus, the on-disk cache may service many disk requests without incurring physical disk access. By exploring the design methodology of on-disk cache, in this paper, we propose cache-aware real-time disk scheduling algorithms that take the on-disk cache into consideration during scheduling. Therefore, the scheduling algorithm can help the cache replacement scheme to minimize the cache miss ratio. Besides, the service timing estimation is more accurate in schedulability analysis since the cache effect is considered during scheduling. A simulation-based evaluation shows the proposed scheduling algorithms to be highly successful as compared with the classical real-time disk scheduling algorithms. For example, under sequential workload with 10 sequential streams, the data throughput of our scheme is 1.1 times that of DM-SCAN.
Enlarged-maximum-scannable-groups for real-time disk scheduling in a multimedia system
(2000)
Chang, HP
;
Chang, RI
;
Shih, WK
;
Chang, RC
;
資訊工程學系
In a multimedia system, disk I/O subsystem is the most important component due to its relatively limited throughput and large delay. Previously, by applying SCAN to reschedule tasks having the same deadline, SCAN-EDF tries to improve disk throughput while realtime constraints call be satisfied. In DM-SCAN, groups of tasks that can be successfully rescheduled by SCAN under specified real-time requirements are identified. They are called MSGs (maximum-scannable-groups). In this paper; an enlarged-MSG (E-MSG) is proposed to further expand the MSG concept and thus to obtain more improvement in disk throughput. By removing some excess constraints on MSG, E-MSG merges several MSGs as a new scannable-group. Experiment results show that the E-MSG scheme is better than both SCAN-EDF and MSG in the disk throughput obtained.
Macro-cell placement fos custom-chip design using self-organizing fuzzy technique
(1998-01-01)
Chang, RI
;
Hsiao, PY
;
資訊工程學系
;
Department of Computer Science
In this paper, a new optimization technique called SOFT (self-organizing fuzzy technique) is proposed to solve the macro-cell placement problem. In SOFT, different criteria are simultaneously accounted by a novel fuzzy gain function which models expert knowledge to control the optimization process. The presented procedure is an adaptation of Kohonen's self-organization algorithm which is well suited for implementation on massively parallel architecture for fast computing. The MCNC benchmark examples are presented to verify the performance and feasibility of SOFT. Comparisons are made with the Hopfield network, SOAP and TimberWolf MC5.6. Experiments show that the proposed method yields an average of 17% improvement in total wire length compared with previous methods. Large size problems with 225 and 1024 arbitrarily-sized macrocells are also presented.
Macro-cell placement fos custom-chip design using self-organizing fuzzy technique
(1998-01-01)
Chang, RI
;
Hsiao, PY
;
資訊工程學系
;
Department of Computer Science
In this paper, a new optimization technique called SOFT (self-organizing fuzzy technique) is proposed to solve the macro-cell placement problem. In SOFT, different criteria are simultaneously accounted by a novel fuzzy gain function which models expert knowledge to control the optimization process. The presented procedure is an adaptation of Kohonen's self-organization algorithm which is well suited for implementation on massively parallel architecture for fast computing. The MCNC benchmark examples are presented to verify the performance and feasibility of SOFT. Comparisons are made with the Hopfield network, SOAP and TimberWolf MC5.6. Experiments show that the proposed method yields an average of 17% improvement in total wire length compared with previous methods. Large size problems with 225 and 1024 arbitrarily-sized macrocells are also presented.
Real-time disk scheduling for multimedia applications with deadline-modification-scan scheme
(2000-09-01)
Chang, RI
;
Shih, WK
;
Chang, RC
;
資訊工程學系
;
Department of Computer Science
Real-time disk scheduling (RTDS) is important for time-critical multimedia applications. In conventional approaches of real-time disk scheduling, such as SCAN-EDF, the seek-optimizing SCAN scheme is applied to reduce the disk service time of the real-time EDF schedule. Since only tasks with the same deadline are seek-optimized, the obtained improvement of SCAN-EDF is limited. In this paper, based on the maximum-scannable-group (MSG) concept, a deadline-modification-scan (DMS or DM-SCAN) algorithm is proposed. Our algorithm uses MSG to automatically decide the suitable task groups for seek-optimizing. Based on the MSG concept, we repeatedly apply DMS to further increase disk throughput to support more tasks. We have implemented the proposed algorithm on UnixWare 2.01. The appropriate problem behaviors and parameter values to yield good solutions are investigated. Experiments show that DMS is better than conventional approaches in both the obtained disk throughput and the supported tasks. Moreover, our proposed approach can schedule task sets that are not schedulable by EDF and SCAN-EDF.
Real-time disk scheduling with on-disk cache conscious
(2003)
Chang, HP
;
Chang, RI
;
Shih, WK
;
Chang, RC
;
資訊工程學系
Previous real-time disk scheduling algorithms assume that each disk request incurs a disk mechanical operation and only consider how to move the disk head under real-time constraints. However, with the increased capacity of on-disk cache, modern disk drives read-ahead data aggressively. Thus, the on-disk cache may service lots of requests without incurring physical disk access. By exploring the design methodology of on-disk cache, in this paper, we propose CARDS: a cache-aware real-time disk scheduling algorithm that takes the on-disk cache into consideration during scheduling. Therefore, the scheduling algorithm can help to minimize the cache miss ratio. Besides, the service timing estimation is more accurate in schedulability analysis since the cache effect is considered. A simulation-based evaluation shows CARDS to be highly successful as compared to the classical real-time disk scheduling algorithms. For example, under sequential workload with 10 sequential streams, the data throughput of CARDS is 1.1 times of DM-SCAN.
Reschedulable-Group-SCAN scheme for mixed real-time/non-real-time disk scheduling in a multimedia system
(2001-11-15)
Chang, HP
;
Chang, RI
;
Shih, WK
;
Chang, RC
;
資訊工程學系
Real-time disk scheduling is important for time-critical multimedia applications. Previous approaches, such as SCAN-earliest deadline first (EDF) or DM-SCAN, applied the SCAN scheme to reschedule service sequence of input tasks to reduce tasks' service time. However, they required the input to be in EDF order. In DM-SCAN, a deadline modification scheme was employed to obtain a pseudo-EDF sequence from non-EDF ordered input tasks. Because the modified deadlines were smaller than the original ones, number of tasks that could be rescheduled is decreased and thus data throughput is reduced. In this paper, we propose Reschedulable-Group-SCAN (RG-SCAN), a new real-time disk scheduling algorithm using the concept of Reschedulable-Group (R-Group). Differing from previous approaches, RG-SCAN has no limitation on the input task's sequence. In addition, by exploiting the service time's reduction after rescheduling in each R-Group, RG-SCAN has been extended to serve mixed real-time and non-real-time workloads. As shown in experimental results. our approach can support more tasks than DM-SCAN, both real-time and non-real-time. Additionally, our approach can provide larger data throughput and offer better response time to non-real-time tasks. For example, given 30 random-generated real-time tasks, the number of non-real-time tasks that can be supported by RG-SCAN is 1.3 times that supported by DM-SCAN. In addition, our data throughput is 1.1 times DM-SCAN's. (C) 2001 Elsevier Science Inc. All rights reserved.
Unsupervised query-based learning algorithm and it's application to Kohonen's seif-organizing maps
(1995)
Chang, RI
;
Hsiao, PY
;
資訊工程學系
;
Department of Computer Science
Unsupervised query-based learning of neural networks using selective-attention and self-regulation
(1997-03-01)
Chang, RI
;
Hsiao, PY
;
交大名義發表
;
資訊工程學系
;
National Chiao Tung University
Query-based learning (QBL) has been introduced for training supervised network model with additional queried samples, Experiments demonstrated that the classification accuracy is further increased. Although QBL has been successfully applied to supervised neural networks, it is not suitable for unsupervised learning models without external supervisors. In this paper, an unsupervised QBL (UQBL) algorithm using selective-attention and self-regulation is proposed. Applying the selective-attention, we can ask the network to respond to its goal-directed behavior with self-focus. Since there is no supervisor to verify the self-focus, a compromise is then made to environment-focus with self-regulation. In this paper, we introduce UQBL1 and UQBL2 as two versions of UQBL; both of them can provide fast convergence. Our experiments indicate that the proposed methods are more insensitive to network initialization. They have better : generalization performance and can be a significant reduction in their training size.
VLSI cell placement on arbitrarily-shaped rectilinear regions using neural networks with calibration nodes
(1995-12-01)
Chang, RI
;
Hsiao, PY
;
交大名義發表
;
資訊工程學系
;
National Chiao Tung University
In VLSI or PCB layout, one often encounters a region that is either of rectilinear shape or can be approximated by a rectilinear region. Although many placement methods have been proposed, most of them are applicable only to rectangular regions. For these algorithms to be applied to a rectilinear region, two processing steps, region partitioning and rectangular region cell placement are necessary. Hence, the placement results are so far dependent on the locations of the regions partitioned and frequently become trapped in local minima. Recently, neural networks have been suggested as a new way to resolve the cell placement problem. This paper proposed a unified modeling method that uses a neural net model with additional calibration nodes to model rectilinear region cell placement. In this method, the ideal distance between cells is preserved to simultaneously minimize both the total wire length and the module overlap. Unlike traditional approaches, the proposed algorithm requires only a single processing step. Experiments have been conducted to verify the performance of the proposed algorithm. The total wire length obtained by our method is shorter than those generated by previous methods.
VLSI circuit placement with rectilinear modules using three-layer force-directed self-organizing maps
(1997-09-01)
Chang, RI
;
Hsiao, PY
;
資訊工程學系
;
Department of Computer Science
In this paper, a three-layer force-directed self-organizing map is designed to resolve the circuit placement problem with arbitrarily shaped rectilinear modules. The proposed neural model with an additional hidden layer can easily model a rectilinear module by a set of hidden neurons to correspond the partitioned rectangles. With the collective computing from hidden neurons, these rectilinear modules can correctly interact with each other and finally converge to a good placement result. In this paper, multiple contradictory criteria are accounted simultaneously during the placement process, in which, both the wire length and the module overlap are reduced. The proposed model has been successfully exploited to solve the time consuming rectilinear module placement problem, The placement results of real rectilinear test examples have been presented, which demonstrate that the proposed method is better than the simulated annealing approach in the total wire length, Furthermore, on the average, the central processing unit (CPU) time for the proposed method running on a sequential machine is 15 times faster than that required by the simulated annealing method, The appropriate parameter values which yield good solutions are also investigated.
VLSI circuit placement with rectilinear modules using three-layer force-directed self-organizing maps
(1997-09-01)
Chang, RI
;
Hsiao, PY
;
資訊工程學系
;
Department of Computer Science
In this paper, a three-layer force-directed self-organizing map is designed to resolve the circuit placement problem with arbitrarily shaped rectilinear modules. The proposed neural model with an additional hidden layer can easily model a rectilinear module by a set of hidden neurons to correspond the partitioned rectangles. With the collective computing from hidden neurons, these rectilinear modules can correctly interact with each other and finally converge to a good placement result. In this paper, multiple contradictory criteria are accounted simultaneously during the placement process, in which, both the wire length and the module overlap are reduced. The proposed model has been successfully exploited to solve the time consuming rectilinear module placement problem, The placement results of real rectilinear test examples have been presented, which demonstrate that the proposed method is better than the simulated annealing approach in the total wire length, Furthermore, on the average, the central processing unit (CPU) time for the proposed method running on a sequential machine is 15 times faster than that required by the simulated annealing method, The appropriate parameter values which yield good solutions are also investigated.