1,302 research outputs found
Future Challenges for HPC Software (GT SSE 2023 Workshop)
No full textDr. Vivek Sarkar presents his vision for future challenges for HPC software at the SSE Scientific Computing Workshop in April 2023.</p
The Eureka Programming Model for Speculative Task Parallelism
No full textIn this paper, we describe the Eureka Programming Model (EuPM) that simplifies the expression of speculative parallel tasks, and is especially well suited for parallel search and optimization applications. The focus of this work is to provide a clean semantics for, and efficiently support, such "eureka-style" computations (EuSCs) in general structured task parallel programming models. In EuSCs, a eureka event is a point in a program that announces that a result has been found. A eureka triggered by a speculative task can cause a group of related speculative tasks to become redundant, and enable them to be terminated at well-defined program points. Our approach provides a bound on the additional work done in redundant speculative tasks after such a eureka event occurs.
We identify various patterns that are supported by our eureka construct, which include search, optimization, convergence, and soft real-time deadlines. These different patterns of computations can also be safely combined or nested in the EuPM, along with regular task-parallel constructs, thereby enabling high degrees of composability and reusability. As demonstrated by our implementation, the EuPM can also be implemented efficiently. We use a cooperative runtime that uses delimited continuations to manage the termination of redundant tasks and their synchronization at join points. In contrast to current approaches, EuPM obviates the need for cumbersome manual refactoring by the programmer that may (for example) require the insertion of if checks and early return statements in every method in the call chain. Experimental results show that solutions using the EuPM simplify programmability, achieve performance comparable to hand-coded speculative task-based solutions and out-perform non-speculative task-based solutions
FIGURE 12 in Description of three new species of the genus Mata Distant, 1906 (Hemiptera Cicadidae: Cicadinae: Oncotympanini) with notes on their natural history from Indian state of Meghalaya, India
No full textFIGURE 12. Mata meghalayana sp. nov. A: Dorsal view of holotype (NCBS-BH999). B: Ventral view of holotype (NCBS-BH999). C: Lateral view of male timbal cover (NCBS-BH999). D: Dorsal view of male timbal covering of holotype (NCBS-BH999). (Copyright and photographed by Vivek Sarkar.)Published as part of Sarkar, Vivek, Mahapatra, Cuckoo, Mohapatra, Pratyush P., Nair, Manoj V. & Kunte, Krushnamegh, 2021, Description of three new species of the genus Mata Distant, 1906 (Hemiptera Cicadidae: Cicadinae: Oncotympanini) with notes on their natural history from Indian state of Meghalaya, India, pp. 1-28 in Zootaxa 4908 (1) on page 23, DOI: 10.11646/zootaxa.4908.1.1, http://zenodo.org/record/443563
FIGURE 10 in Description of three new species of the genus Mata Distant, 1906 (Hemiptera Cicadidae: Cicadinae: Oncotympanini) with notes on their natural history from Indian state of Meghalaya, India
No full textFIGURE 10. Mata meghalayana sp. nov. A: Lateral view of holotype in habitus (NCBS-BH999). B: Dorsal view of holotype in habitus (NCBS-BH999). C: Ventral view of holotype in habitus (NCBS-BH999). D: Close up dorsal view of holotype in habitus (NCBS-BH999). (Copyright and photographed by Vivek Sarkar.)Published as part of Sarkar, Vivek, Mahapatra, Cuckoo, Mohapatra, Pratyush P., Nair, Manoj V. & Kunte, Krushnamegh, 2021, Description of three new species of the genus Mata Distant, 1906 (Hemiptera Cicadidae: Cicadinae: Oncotympanini) with notes on their natural history from Indian state of Meghalaya, India, pp. 1-28 in Zootaxa 4908 (1) on page 21, DOI: 10.11646/zootaxa.4908.1.1, http://zenodo.org/record/443563
A new species of Ahaetulla Link, 1807 (Serpentes: Colubridae: Ahaetullinae) from India
No full textDeepak, V., Narayanan, Surya, Sarkar, Vivek, Dutta, Sushil K., Mohapatra, Pratyush P. (2019): A new species of Ahaetulla Link, 1807 (Serpentes: Colubridae: Ahaetullinae) from India. Journal of Natural History 53 (9): 497-516, DOI: 10.1080/00222933.2019.158959
A new species of Sitana (Squamata: Agamidae) from the Deccan Peninsula Biogeographic Zone of India
No full textDeepak, V., Tillack, Frank, Kar, Niladri B., Sarkar, Vivek, Mohapatra, Sh. P. (2021): A new species of Sitana (Squamata: Agamidae) from the Deccan Peninsula Biogeographic Zone of India. Zootaxa 4948 (2): 261-274, DOI: https://doi.org/10.11646/zootaxa.4948.2.
Linear Promises: Towards Safer Concurrent Programming (Artifact)
No full textWe present a compiler for a concurrent programming language, which utilizes linear typing to create a safer promise abstraction. The compiler is implemented in OCaml and produces source-level Java code. We provide example programs to demonstrate use of the language, as well as translations of incorrect JavaScript code from StackOverflow to showcase the ability of our language to catch many classes of bugs. Finally, we provide a minimal runtime environment to allow the execution of compiled programs
Figure 4 in A new species of Ahaetulla Link, 1807 (Serpentes: Colubridae: Ahaetullinae) from India
No full textFigure 4. Ahaetulla laudankia sp. nov. Paratype sub-adult male (ZSI-R-26412) from Madhapur, Boudh district, Odisha state.Published as part of Deepak, V., Narayanan, Surya, Sarkar, Vivek, Dutta, Sushil K. & Mohapatra, Pratyush P., 2019, A new species of Ahaetulla Link, 1807 (Serpentes: Colubridae: Ahaetullinae) from India, pp. 497-516 in Journal of Natural History 53 (9) on page 508, DOI: 10.1080/00222933.2019.1589591, http://zenodo.org/record/367568
Dynamic Determinacy Race Detection for Task-Parallel Programs with Promises
No full textMuch of the past work on dynamic data-race and determinacy-race detection algorithms for task parallelism has focused on structured parallelism with fork-join constructs and, more recently, with future constructs. This paper addresses the problem of dynamic detection of data-races and determinacy-races in task-parallel programs with promises, which are more general than fork-join constructs and futures. The motivation for our work is twofold. First, promises have now become a mainstream synchronization construct, with their inclusion in multiple languages, including C++, JavaScript, and Java. Second, past work on dynamic data-race and determinacy-race detection for task-parallel programs does not apply to programs with promises, thereby identifying a vital need for this work.
This paper makes multiple contributions. First, we introduce a featherweight programming language that captures the semantics of task-parallel programs with promises and provides a basis for formally defining determinacy using our semantics. This definition subsumes functional determinacy (same output for same input) and structural determinacy (same computation graph for same input). The main theoretical result shows that the absence of data races is sufficient to guarantee determinacy with both properties. We are unaware of any prior work that established this result for task-parallel programs with promises. Next, we introduce a new Dynamic Race Detector for Promises that we call DRDP. DRDP is the first known race detection algorithm that executes a task-parallel program sequentially without requiring the serial-projection property; this is a critical requirement since programs with promises do not satisfy the serial-projection property in general. Finally, the paper includes experimental results obtained from an implementation of DRDP. The results show that, with some important optimizations introduced in our work, the space and time overheads of DRDP are comparable to those of more restrictive race detection algorithms from past work. To the best of our knowledge, DRDP is the first determinacy race detector for task-parallel programs with promises
Robust decentralized authentication for public keys and geographic location:
No full textAuthentication has traditionally been done either in a decentralized manner with human assistance or automatically through a centralized security infrastructure. In the security infrastructure approach, a central trusted authority takes on the responsibility of authenticating participants within its domain of control. While the security infrastructure approach works well in traditional organizations, it does not address the needs of open membership systems.
We propose automatic decentralized authentication mechanisms for peer-to-peer systems, email systems, and ad-hoc networks. Our byzantine fault tolerant public-key authentication protocol (BPKA) provides decentralized authentication to peer-to-peer systems with honest majority. Authentication is done over an insecure asynchronous network without using trusted third parties or human input. We also authenticate public keys in the email environment through our social-group key authentication protocol (SGKA). The protocol provides end-to-end authentication at the email client without using infrastructure or centralized authorities. Finally, location authentication in ad-hoc networks is proposed through our geographical secure path routing protocol (GSPR). The protocol authenticates geographic locations of anonymous nodes in order to provide location authentication and anonymity simultaneously.Ph.D.Includes bibliographical references (p. 121o-128)by Vivek Patha
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