A visualization system for parallelizing programs

Discovering which code sections in a sequential program can be made to run in parallel is the first step in parallelizing it, and programmers routinely struggle in this step. Most of the current parallelism discovery techniques focus on specific language constructs while trying to identify such code sections. In contrast, we propose to concentrate on the computations performed by a program. In our approach, a program is treated as a collection of computations communicating with one another using a number of variables. Each computation is represented as a Computational Unit (CU). A CU contains the inputs and outputs of a computation, and the three phases of a computation: read, compute, and write. Based on the notion of CU, We present a unified framework to identify both loop and task parallelism in sequential programs.

Parallelization of sequential programs is often daunting because of the substantial development cost involved. Previous solutions have not always been successful, partly because many try to address all types of applications. We propose a platform for parallelization of a class of applications that have similar computational structure, namely graph-structured iterative applications. iC2mpi is a unique proof-of-concept prototype platform that provides relatively easy parallelization of existing sequential programs and facilitates experimentation with static partitioning and dynamic load balancing schemes. We demonstrate with various generic application graph topologies that our platform can produce good performance with very little effort. The iC2mpi platform has a good potential for further performance improvements and for extensions to related classes of application domains.

While a canonical out-of-order engine can effectively exploit implicit parallelism in sequential programs, its effectiveness is often hindered by instruction and data supply imperfections manifested as branch mispredictions and cache misses. Accurate and deep look-ahead guided by a slice of the executed program is a simple yet effective approach to mitigate the performance impact of branch mispredictions and cache misses. Unfortunately, program slice-guided look ahead is often limited by the speed of the look-ahead code slice, especially for irregular programs. In this paper, we attempt to speed up the look-ahead agent using speculative parallelization, which is especially suited for the task. First, slicing for look-ahead tends to reduce important data dependences that prohibit successful speculative parallelization. Second, the task for look-ahead is not correctness critical and thus naturally tolerates dependence violations. This enables an implementation to forgo violation detection altogether, simplifying architectural support tremendously. In a straightforward implementation, incorporating speculative parallelization to the look-ahead agent further improves system performance by up to 1.39x with an average of 1.13x.

The parallelizing transformation (hand-crafted or compiler-assisted) is error prone as it is often performed without verifying any semantic equivalence with the sequential counterpart. Even when the parallel program can be proved to be semantically equivalent with its corresponding sequential program, detecting data-race conditions in the parallel program remains a challenge. In this paper, we propose a formal verification approach that can detect data-race conditions while verifying the computational semantic equivalence of parallelizing loop transformations. We propose a coloured array data dependence graph (C-ADDG) based modeling of a program for verification of program equivalence as well as data-race condition detection across parallel loops. We have tested our tool on a set of Rodinia and PLuTo+ benchmarks and shown that our method is sound, whereby the method does not produce any false-positive program equivalence or data-race condition.

Many modelling languages have both a textual and a graph- ical form. The relationship between these two forms ought to be clear and concrete, but is instead commonly underspecified, weak, and infor- mal. Further, processes and tool support for modelling often do not treat both forms as first-class citizens, instead choosing to favour one as the “real” representation and the other as a derivable representation.<br/>As textual and graphical forms have their individual strengths and weak- nesses, ideally one should be able to view and edit a model in whichever form is most desirable at the moment. Furthermore, we should be able to do so without having to worry about semantic differences between what is seen in a graphical view versus what is seen in a textual view. If we are to develop tools that allow dual-editing—simultaneous editing of both the textual and graphical forms—then it is essential that their relationship is clearly and precisely defined.<br/>This paper details a formal relationship between the textual and graph- ical forms of a high-level modelling language called the Business Object Notation (BON). We describe the semantics of the graphical and textual representations and the relationship that holds between them. We also formally define a view on an underlying model as an extraction func- tion, and model diffs as a means of tracking changes as a model evolves. This theoretical foundation provides a means by which tools guarantee consistency between textual and graphical notations, as well shows how to efficiently perform model updates, reason about model views, and interpret properties between modelling perspectives.

The performance of data parallel programs often hinges on two key coordination aspects: the computational costs of the parallel tasks relative to their management overhead — task granularity; and the communication costs induced by the distance between tasks and their data — data locality. In data parallel programs both granularity and locality can be improved by clustering, i.e. arranging for parallel tasks to operate on related sub-collections of data.The GPH parallel functional language automatically manages most coordination aspects, but also allows some high-level control of coordination using evaluation strategies. We study the coordination behavior of two typical data parallel programs, and find that while they can be improved by introducing clustering evaluation strategies, further performance improvements can be achieved by restructuring the program.We introduce a new generic Cluster class that allows clustering to be systematically introduced, and improved by program transformation. In contrast to many other parallel program transformation approaches, we transform realistic programs and report performance results on a 32-processor Beowulf cluster. The cluster class is highly-generic and extensible, amenable to reasoning, and avoids conflating computation and coordination aspects of the program.

The estimation and control of resource usage is now an important challenge in an increasing number of computing systems. In particular, requirements on timing and energy arise in a wide variety of applications such as internet of things, cloud computing, health, transportation, and robots. At the same time, parallel computing, with (heterogeneous) multi-core platforms in particular, has become the dominant paradigm in computer architecture. Predicting resource usage on such platforms poses a difficult challenge. Most work on static resource analysis has focused on sequential programs, and relatively little progress has been made on the analysis of parallel programs, or more specifically on parallel logic programs. We propose a novel, general, and flexible framework for setting up cost equations/relations which can be instantiated for performing resource usage analysis of parallel logic programs for a wide range of resources, platforms, and execution models. The analysis estimates both lower and upper bounds on the resource usage of a parallel program (without executing it) as functions on input data sizes. In addition, it also infers other meaningful information to better exploit and assess the potential and actual parallelism of a system. We develop a method for solving cost relations involving the max function that arise in the analysis of parallel programs. Finally, we instantiate our general framework for the analysis of logic programs with Independent And-Parallelism, report on an implementation within the CiaoPP system, and provide some experimental results. To our knowledge, this is the first approach to the cost analysis of parallel logic programs.

Although code transformations are routinely applied to improve the performance of programs for both scalar and parallel machines, the properties of code-improving transformations are not well understood. In this article we present a framework that enables the exploration, both analytically and experimentally, of properties of code-improving transformations. The major component of the framework is a specification language, Gospel, for expressing the conditions needed to safely apply a transformation and the actions required to change the code to implement the transformation. The framework includes a technique that facilitates an analytical investigation of code-improving transformations using the Gospel specifications. It also contains a tool, Genesis, that automatically produces a transformer that implements the transformations specified in Gospel. We demonstrate the usefulness of the framework by exploring the enabling and disabling properties of transformations. We first present analytical results on the enabling and disabling properties of a set of code transformations, including both traditional and parallelizing transformations, and then describe experimental results showing the types of transformations and the enabling and disabling interactions actually found in a set of programs.

Parallel programming on multi-core processors has become the industry's biggest software challenge. This paper proposes a novel parallel architecture for executing sequential programs using multi-core pipelining based on program slicing by a new memory/cache dynamic management technology. The new architecture is very suitable for processing large geospatial data in parallel without parallel programming. This paper presents a new architecture for parallel computation that addresses the problem of needing to relocate data from one memory hierarchy to another in a multi-core environment. A new memory management technology inserts a layer of abstraction between the processor and the memory hierarchy, allowing the data to stay in one place while the processor effectively migrates as tasks change. The new architecture can make full use of the pipeline and automatically partition data then schedule them onto multi-cores through the pipeline. The most important advantage of this architecture is that most existing sequential programs can be directly used with nearly no change, unlike conventional parallel programming which has to take into account scheduling, load balancing, and data distribution. The new parallel architecture can also be successfully applied to other multi-core/many-core architectures or heterogeneous systems. In this paper, the design of the new multi-core architecture is described in detail. The time complexity and performance analysis are discussed in depth. The experimental results and performance comparison with existing multi-core architectures demonstrate the effectiveness, flexibility, and diversity of the new architecture, in particular, for large geospatial data parallel processing with the examples of Digital Elevation Model (DEM) generation from Light Detection And Ranging (LIDAR) dataset.

Discovery of parallelization opportunities in sequential programs can greatly reduce the time and effort required to parallelize any application. Identification and analysis of code that contains little to no internal parallelism can also help expose potential parallelism. This paper provides a technique to identify a block of code called Computational Unit (CU) that performs a unit of work in a program. A CU can assist in discovering the potential parallelism in a sequential program by acting as a basic building block for tasks. CUs are used along with dynamic analysis information to identify the tasks that contain tightly coupled code within them. This process in turn reveals the tasks that are weakly dependent or independent. The independent tasks can be run in parallel and the dependent tasks can be analyzed to check if the dependences can be resolved. To evaluate our technique, different benchmark applications are parallelized using our identified tasks and the speedups are reported. In addition, existing parallel implementations of the applications are compared with the identified tasks for the respective applications.

The growing number of processing cores in a single CPU is demanding more parallelism from sequential programs. But in the past decades few work has succeeded in automatically exploiting enough parallelism, which casts a shadow over the many-core architecture and the automatic parallelization research. However, actually few work was tried to understand the nature, or amount, of the potentially available parallelism in programs. In this paper we will analyze at runtime the dynamic data dependencies among superblocks of sequential programs. We designed a meta re-arrange buffer to measure and exploit the available parallelism, with which the superblocks are dynamically analyzed, reordered and dispatched to run in parallel on an ideal many-core processor, while the data dependencies and program correctness are still maintained. In our experiments, we observed that with the superblock reordering, the potential speedup ranged from 1.08 to 89.60. The results showed that the potential parallelism of normal programs was still far from fully exploited by existing technologies. This observation makes the automatic parallelization a promising research direction for many-core architectures.

Language generally appears in the linguistic and non-linguistic social process. Language always comes in the form of text, because language in text form is always the realization of a verbal, whether it be central or dominant as in the linguistic and social process that are peripheral or that complements the non-linguistic processes. Language in the form of text always brings social functions of a social process in a society. As well as this Durangpo Puppet discourse that tells about the social life and political disputes. In the story the author reveals more use of stylistic allusions and figures used in the story is to use the puppet characters. So interesting to be observised if Discourse Puppet Durangpo analyzed in terms of form and meaning of satire. The base of the theory used in this study is the theory of satire which consists of three kinds of irony, cynicism and sarcasm. The method used in this research is descriptive qualitative approach. Because this study describes the results of research through words. Data collected in the form of text containing Durangpo discourse Puppet satire. Data collection is done by reading the text and notes. From reading research techniques to collect data, which are words or phrases that contain allusions are then grouped and coded data. The data has been further interpreted in the form of exposure dieksplanasi language as a result of an analysis. The results obtained from this study is the insinuation in Puppet Durangpo to know the shape and meaning of satire contained in Puppet Durangpo discourse. Meaning contained in the discourse lead to more Durangpo Puppet social and political criticism.

Heuristics for calculating phylogenetic trees for a large sets of aligned rRNA sequences based on the maximum likelihood method are computationally expensive. The core of most parallel algorithms, which accounts for the greatest part of computation time, is the tree evaluation function, that calculates the likelihood value for each tree topology. This paper describes and uses Subtree Equality Vectors (SEVs) to reduce the number of required floating point operations during topology evaluation. We integrated our optimizations into various sequential programs and into parallel fastDNAml, one of the most common and efficient parallel programs for calculating large phylogenetic trees. Experimental results for our parallel program, which renders exactly the same output as parallel fastDNAml show global runtime improvements of 26% to 65%. The optimization scales best on clusters of PCs, which also implies a substantial cost saving factor for the determination of large trees.

During the software crisis of the 1960s, Dijkstra’s famous thesis “goto considered harmful” paved the way for structured programming. In this paper that is a modified version of the short communication [10], we suggest that many current difficulties of parallel programming based on message passing are caused by poorly structured communication, which is a consequence of using low-level send-receive primitives. We argue that, like goto in sequential programs, send-receive should be avoided as far as possible and replaced by collective operations in the setting of message passing. We dispute some widely held opinions about the apparent superiority of low-level, pairwise primitives over collective operations, and we present substantial theoretical and empirical evidence to the contrary in the context of MPI (Message Passing Interface).

Parallel computation of recoupling coefficients using transputers