DRUM Collection: Electrical & Computer Engineering Research Workshttp://hdl.handle.net/1903/16582015-05-29T20:14:45Z2015-05-29T20:14:45ZOn Number Of Partitions Of An Integer Into A Fixed Number Of Positive IntegersOruc, A. Yavuzhttp://hdl.handle.net/1903/163512015-05-28T13:34:40Z2015-04-01T00:00:00ZTitle: On Number Of Partitions Of An Integer Into A Fixed Number Of Positive Integers
Authors: Oruc, A. Yavuz
Abstract: This paper focuses on the number of partitions of a positive integer $n$ into $k$ positive summands, where $k$ is an integer between $1$ and $n$. Recently some upper bounds were reported for this number in [Merca14]. Here, it is shown that these bounds are not as tight as an earlier upper bound proved in [Andrews76-1] for $k\le 0.42n$. A new upper bound for the number of partitions of $n$ into $k$ summands is given, and shown to be tighter than the upper bound in [Merca14] when $k$ is between $O(\frac{\sqrt{n}}{\ln n})$ and $n-O(\frac{\sqrt{n}}{\ln n})$. It is further shown that the new upper bound is also tighter than two other upper bounds previously reported in~[Andrews76-1] and [Colman82]. A generalization of this upper bound to number of partitions of $n$ into at most $k$ summands is also presented.
Description: Submitted to Journal of Number Theory.2015-04-01T00:00:00ZFeasibility Study of Scaling an XMT Many-CoreO'Brien, SeanVishkin, UziEdwards, JamesWaks, EdoYang, Baohttp://hdl.handle.net/1903/163162015-02-27T03:30:10Z2015-01-19T00:00:00ZTitle: Feasibility Study of Scaling an XMT Many-Core
Authors: O'Brien, Sean; Vishkin, Uzi; Edwards, James; Waks, Edo; Yang, Bao
Abstract: The reason for recent focus on communication avoidance is that high rates of data movement become infeasible due to excessive power dissipation. However, shifting the responsibility of minimizing data movement to the parallel algorithm designer comes at significant costs to programmer’s productivity, as well as: (i) reduced speedups and (ii) the risk of repelling application developers from adopting parallelism.
The UMD Explicit Multi-Threading (XMT) framework has demonstrated advantages on ease of parallel programming through its support of PRAM-like programming, combined with strong, often unprecedented speedups. Such programming and speedups involve considerable data movement between processors and shared memory. Another reason that XMT is a good test case for a study of data movement is that XMT permits isolation and direct study of most of its data movement (and its power dissipation).
Our new results demonstrate that an XMT single-chip many-core processor with tens of thousands of cores and a high throughput network on chip is thermally feasible, though at some cost. This leads to a perhaps game-changing outcome: instead of imposing upfront strict restrictions on data movement, as advocated in a recent report from the National Academies, opt for due diligence that accounts for the full impact on cost. For example, does the increased cost due to communication avoidance (including programmer’s productivity, reduced speedups and desertion risk) indeed offset the cost of the solution we present?
More specifically, we investigate in this paper the design of an XMT many-core for 3D VLSI with microfluidic cooling. We used state-of-the-art simulation tools to model the power and thermal properties of such an architecture with 8k to 64k lightweight cores, requiring between 2 and 8 silicon layers. Inter-chip communication using silicon compatible photonics is also considered. We found that, with the use of microfluidic cooling, power dissipation becomes a cost issue rather than a feasibility constraint.
Robustness of the results is also discussed.2015-01-19T00:00:00ZWhite paper: Towards a Second Line of Defense for Computer SecurityVishkin, Uzihttp://hdl.handle.net/1903/150832014-06-16T12:31:31Z2013-04-30T00:00:00ZTitle: White paper: Towards a Second Line of Defense for Computer Security
Authors: Vishkin, Uzi
Abstract: Much academic research on computer security has followed a perfectionist approach, seeking a system so secure that it cannot be penetrated. However, in reality security is breached and systems are penetrated. This working paper outlines some preliminary concepts for thinking about such less fortunate circumstances. It also reviews a hardware mechanism called security master for addressing them.2013-04-30T00:00:00ZObtaining Statistically Random Information from Silicon Physical Unclonable FunctionsYin, Chi-EnQu, Ganghttp://hdl.handle.net/1903/150002014-05-21T13:59:16Z2013-01-01T00:00:00ZTitle: Obtaining Statistically Random Information from Silicon Physical Unclonable Functions
Authors: Yin, Chi-En; Qu, Gang
Abstract: Silicon physical unclonable functions (PUF) uti- lize the variation during silicon fabrication process to extract information that will be unique for each chip. There have been many recent approaches to how PUF can be used to improve security related applications. However, it is well-known that the fabrication variation has very strong spatial correlation1 and this has been pointed out as a security threat to silicon PUF. In fact, when we apply NIST’s statistical test suite for randomness [1] against the random sequences generated from a population of 125 ring oscillator (RO) PUFs [2] using classic 1-out-of-8 Coding [3], [4] and Neighbor Coding [5], none of them can pass all the tests. In this paper, we propose to decouple the unwanted systematic variation from the desired random variation through a regression-based distiller, where the basic idea is to build a model for the systematic variation so we can generate the random sequences only from the true random variation. Applying Neighbor Coding to the same benchmark data [2], our experiment shows that 2nd and 3rd order polynomials distill random sequences that pass all the NIST randomness tests. So does 4th order polynomial in the case of 1-out-of-8 Coding. Finally, we introduce two generic random sequence generation methods. The sequences they generate fail all the randomness tests, but with the help of our proposed polynomial distiller, all but one tests are passed. These results demonstrate that our method can provide statistically random PUF information and thus bolster the security characteristics of existing PUF schemes.2013-01-01T00:00:00Z