Difference between control flow and data flow i m dba. In this paper, we propose the rescheduling of the entire application to minimize throughput degradation under a latency constraint, given that the application is specified by a. Synchronous dataflow graphs originally developed in lee and messerschmitt, 1987, asynchronousdataflow graph sdfg is a finite, directed, weighted graph g v,e,d,t,p,k where 1. Consequently, their design is getting more complicated. Nodes within sdf graphs represent computation while arcs represent dependencies between nodes. Parallelizing synchronous dataflow graphs via retiming. It is only now, with embedded software becoming increasingly.
Synchronous dataflow the first part of this lecture introduced the synchronous dataflow model of computation. We obtain suboptimal rescheduling results using a genetic algorithm for each scenario of processor failures at compiletime. Static optimal scheduling for synchronous data flow graphs. Using a graph representation, sdf graphs formally specify a dataflow algorithm without any assumptions on the final implementation. Output ports are connected to input ports via onetoone fifo channels. Interfacebased hierarchy for synchronous dataflow graphs. The nodes in the synchronous dataflow graph are actors that use a firing rule. Synchronous dataflow is a restriction of kahn process networks where nodes produce and consume a fixed number of data items per firing. Under the data flow paradigm, algorithms are described as directed graphs where the nodes represent computations or functions and the arcs represent data paths.
Synchronous dataflow and visual programming for prototyping. Individual scenarios are synchronous dataflow graphs. Applying realtime scheduling theory to the synchronous data. Transforming synchronous dataflow graphs to reduce. To create a reusable piece of software, it is important to maximize. Any process consisting of multiple tasks where the tasks must be executed in sequence, but one must be executed on another machine fetch andor update data, get a stock quote from financial service, etc. The main result of this work is an iteration bound equation for finding an integral static schedule for a sdfg, in which a node is issued at the beginning of a. Synchronous transfer is when data is generated at a constant rate using a shared periodic clock. In this paper, we propose the rescheduling of the entire application to minimize throughput degradation under a latency constraint, given that the application is specified by a synchronous data flow sdf graph. Equivalence of transformations of synchronous data flow. In this section the basic properties of the synchronous data flow graphs will be summarized. Static scheduling of synchronous data flow programs for digital. In a data flow graph, nodes, called actors, represent operations functions and predicates to be applied to data objects, and arcs represent channels for data objects to move from a producing actor to a consuming actor. An actor consists of a set of input ports, a set of output ports, and a.
Modeling pipelined application with synchronous data flow graphs. Tuple synchronous data flow sdf is a special case of data flow 26, a hardware and software methodology popular among computer scientists for parallel computation. Process oriented doesnt manage or pass data between components. V r is a function giving the execution delay of a node, and. Data flow graph dfg a modem communications system each box is a single function or sub systems the activity of each block in the chain depends on the input of the previous block data driven each functional block may have to wait until it receives a certain amount of information before it begins processing some place to output. Jul 12, 2016 synchronous transfer is when data is generated at a constant rate using a shared periodic clock. The synchronous data flow model is useful to capture multirate signal processing systems. Some authors use the term datastream instead of dataflow to avoid confusion with dataflow.
Synchronous communications and timing configurations in. Data flow graph dfg a modem communications system each box is a single function or sub systems the activity of each block in the chain depends on the input of the previous block data. However, despite its proven effectiveness in transforming singlerate data flow graphs to equivalent dfgs with smaller clock periods, the use. Write a fibonacci number generator using synchronous data flow model pseudo code for each node in sdf using peek,push and pop statements push token. This thesis addresses the issue of determining the iteration bound for a synchronous data flow graph sdfg and determining whether or not a sdfg is live. Let us understand the basic difference between control flow and data flow in ssis 2005. Data memory minimisation for synchronous data flow. Each actor pin the graph is associated with an activation clock p. In computer programming, dataflow programming is a programming paradigm that models a program as a directed graph of the data flowing between operations, thus implementing dataflow principles and architecture. Keywords synchronous dataflow graphs, scheduling, selftimed execution, multicore systems acm reference format. Transforming synchronous dataflow graphs to reduce execution. Download scientific diagram simple example of a synchronous data flow. We give precedence to codesize minimization in this book. Failureaware task scheduling of synchronous data flow graphs.
Pdf parallelizing synchronous dataflow graphs via retiming. Synchronous data flow sdf is a special case of data flow either. Feb 07, 2016 transformations inside of a ssis data flow task fall into two categories. Sdf is particularly wellsuited for signal processing and. This book studies the problem of generating software implementations that are both program and buffermemory optimal for programmable dsps starting from applications expressed as synchronous dataflow graphs.
Synchronous dataflow sdf has the advantage that algorithms expressed as consistent. Figure 2 shows an example of an ibsdf graph, where the top level. Throughput constraint for synchronous data flow graphs. If its on a separate machine it is on a separate thread, whether synchronous or asynchronous. For example, synchronous data flow lee 1987 is a special case of process networks that imposes the constraint in which the number of input and output tokens consumed and produced by each process is. In a data flow graph, nodes, called actors, represent operations functions. Traditionally, a program is modelled as a series of operations happening in a specific order. Embedded software systems course synchronous dataflow. Systemvue simulation environment is built based on data flow models of computation data flow models of computation. In the data flow modeling paradigm, the computational behavior of a system is represented as a directed graph. Asynchronous vs synchronous execution, what does it really. Dependencies between subsequent scenarios are captured by tokens which are transferred from one graph to the next. Latency minimization for synchronous data flow graphs a.
Any process consisting of multiple tasks where the tasks must be executed in sequence, but one must be executed on another machine fetch andor update data, get a stock. Its precisely this feature that makes them so useful for hardwaresoftware. Dataflow programming languages share some features of functional languages, and were generally developed in order to bring some functional concepts to a language more suitable for numeric processing. For a more detailed description of the sdf properties the user should refer to the literature 1. Theelen eindhoven university of technology, electronic systems group a. A data flow graph is a graph model for computer programs that expresses possibilities for concurrent execution of program parts.
Theelen eindhoven university of technology, electronic systems group. Introduction to data flow simulation systemvue 2010. Index termsblock diagram, computation graphs, data flow digital signal processing, hard realtime. Does not need information about any other rows inside the data set. Synchronous data flow graphs sdfgs are a very useful means for modeling and analyzing streaming applications. Data flow diagramdfd introduction, dfd symbols and levels in dfd software engineering hindi duration.
Synchronous dataflow sdf graphs are a convenient way to represent many signal processing and dataflow operations. Data flow is a natural paradigm for describing dsp applications for concurrent implementation on parallel hardware. A great deal of research has been done attempting to optimize such applications through retiming. Pdf throughput analysis of synchronous data flow graphs. Retiming and unfolding are important graph transformation techniques for performance optimization of sdfgs. Synchronous data flow graphs sdfgs are a useful tool for modeling and analyzing embedded data flow applications, both in a single processor and a multiprocessing context or for application mapping on platforms. Nodes within sdf graphs represent computation while arcs represent. In source synchronous synchronization a common clock synchronizes communication. Hardware synthesis of synchronous data flow models by.
Transformations inside of a ssis data flow task fall into two categories. The transmitting device sends the clock signal to the. That is, algorithms expressed as sdf graphs can always be converted into. An sdf graph is a directed graph g v e d p c w,inwhich d. Synchronous transformations usually have the following characteristics. Citeseerx document details isaac councill, lee giles, pradeep teregowda. Synchronous data flow scenarios1 eindhoven university. In short, the application is represented as a directed graph gn,e, where the nodes n represent computation tasks, and the edges e the com. Data memory minimisation for synchronous data flow graphs. Synchronous data flow graphs originally developed in lee and messerschmitt, 1987, asynchronousdata flow graph sdfg is a finite, directed, weighted graph g v,e,d,t,p,k where 1. V is the vertex set of nodes that transform input data streams into output streams. We explicitly model algorithmic parameters in the dataflow graph, which results in a more. Edges are labeled with their token production and consumption rates. Static optimal scheduling for synchronous data flow graphs with model checking.
Synchronous data flow graphs sdfgs are widely used to model digital signal processing dsp algorithms and streaming applications. They have been used in sequential dsp applications 3, 20. For example, synchronous data flow lee 1987 is a special case of process networks that imposes the constraint in which the number of input and output tokens consumed and produced by each process is statically determined to be constant. Mar 23, 2017 data flow diagramdfd introduction, dfd symbols and levels in dfd software engineering hindi duration.
Jun 23, 2008 let us understand the basic difference between control flow and data flow in ssis 2005. Data flow programs for signal processing are directed graphs where each node represents a function and each arc represents a signal path. Synchronous data flow sdf is a special case of data flow 26, a hardware and software methodology popular among computer scientists for parallel computation. It functions as a task coordinator in control flow tasks requires completion success. Synchronous data flow graphs sdfgs are a useful tool for modeling and analyzing embedded data flow applications, both in a single processor and a multiprocessing context or for application. Synchronous data flow sdf graphs, widely adopted to describe streaming applications, naturally model only their partitioning, so they usually have to be integrated with other types of. Sdf is particularly wellsuited for signal processing and multimedia applications and has been extensively studied over the years e. Synchronous data flow graph the synchronous data flow sdf graph 4 is used to simplify the application speci. Citeseerx nearoptimal scheduling of synchronous dataflow. Synchronous data flow graph sdfg 15 modeling abstraction1, proves more challenging.
Throughput analysis of synchronous data flow graphs. We analyze the throughput of the constructed model, make tradeo between throughput and bu er size. Synchronous data flow graphs sdfgs are a useful tool for modeling and analyzing embedded data flow applications, both in a single processor and a multiprocessing context or for application mapping. Communicationaware scheduling algorithms for synchronous dataflow graphs on multicore systems. Timinganalysis of synchronous data flow graphs consumer electronic systems are getting more and more complex. Recently, languages based on sdf, such as streamit 21. Synchronous dataflow sdf has the advantage that algorithms expressed as consistent sdf graphs can always be converted into an implementation that is guaranteed to take finitetime to complete all tasks and use finite memory, provided that individual sdf actors take finite time and. Data flow diagrams solution extends conceptdraw diagram or later with templates, samples and libraries of design elements for drawing data flow diagrams dfds. The data and control signals are generated relative to the clock edge. This book studies the problem of generating software implementations that are both program and buffermemory optimal for programmable dsps starting from applications expressed as synchronous. Latency minimization for synchronous data flow graphs. Synchronous or static data flow sdf models 6 is a successful model in this domain, particularly for signal processing and multimedia applications. Synchronous dataflow sdf is a model first proposed by edward a. Aug 06, 2017 software and testing training 198,110 views.
Interfacebased synchronous dataflow graph ibsdf 6 is a static hierarchical data. Synchronous dataflow is a model of computation, a highlevel model that comes with precise rules of execution. Synchronous data flow sdf is a special case of data flow either atomic or large grain in which the number of data samples produced or consumed by each node on each invocation is specified a priori. Synchronous data flow sdf is represented as a graph. Memory bounds for the distributed execution of a hierarchical. Ppt animation to show how the tokens flow in sdf graph periodic schedule of the sdf 41. Eindhoven university of technology master synchronous. Communicationaware scheduling algorithms for synchronous. Any valid sdfg can be converted to an equivalent homogenous sdfg hsdfg. Youre already familiar with one other very popular model of computation called finite state. A widespread model of computation in this domain is synchronous or static data flow sdf 14.
677 706 541 1195 1149 516 1164 20 1538 637 457 329 471 281 160 1273 209 1120 391 167 616 1363 981 510 569 401 1354 80 1266 329 1575 915 1151 282 1051 1244 187 192 621 572 1197 771