Optimal Placement Algorithms for Virtual Machines

Cloud computing provides a computing platform for the users to meet their demands in an efficient, cost-effective way. Virtualization technologies are used in the clouds to aid the efficient usage of hardware. Virtual machines (VMs) are utilized to satisfy the user needs and are placed on physical machines (PMs) of the cloud for effective usage of hardware resources and electricity in the cloud. Optimizing the number of PMs used helps in cutting down the power consumption by a substantial amount. In this paper, we present an optimal technique to map virtual machines to physical machines (nodes) such that the number of required nodes is minimized. We provide two approaches based on linear programming and quadratic programming techniques that significantly improve over the existing theoretical bounds and efficiently solve the problem of virtual machine (VM) placement in data centers

Actors that Unify Threads and Events

There is an impedance mismatch between message-passing concurrency and virtual machines, such as the JVM. VMs usually map their threads to heavyweight OS processes. Without a lightweight process abstraction, users are often forced to write parts of concurrent applications in an event-driven style which obscures control flow, and increases the burden on the programmer. In this paper we show how thread-based and event-based programming can be unified under a single actor abstraction. Using advanced abstraction mechanisms of the Scala programming language, we implemented our approach on unmodified JVMs. Our programming model integrates well with the threading model of the underlying VM

Evaluating Cache Coherent Shared Virtual Memory for Heterogeneous Multicore Chips

The trend in industry is towards heterogeneous multicore processors (HMCs), including chips with CPUs and massively-threaded throughput-oriented processors (MTTOPs) such as GPUs. Although current homogeneous chips tightly couple the cores with cache-coherent shared virtual memory (CCSVM), this is not the communication paradigm used by any current HMC. In this paper, we present a CCSVM design for a CPU/MTTOP chip, as well as an extension of the pthreads programming model, called xthreads, for programming this HMC. Our goal is to evaluate the potential performance benefits of tightly coupling heterogeneous cores with CCSVM

Rain VM: Portable Concurrency through Managing Code

A long-running recent trend in computer programming is the growth in popularity of virtual machines. However, few have included good support for concurrency - a natural mechanism in the Rain programming language. This paper details the design and implementation of a secure virtual machine with support for concurrency, which enables portability of concurrent programs. Possible implementation ideas of many-to-many threading models for the virtual machine kernel are discussed, and initial benchmarks are presented. The results show that while the virtual machine is slow for standard computation, it is much quicker at running communication-heavy concurrent code - within an order of magnitude of the same native code

The Ontological Basis of Strong Artificial Life

This article concerns the claim that it is possible to create living organisms, not merely models that represent organisms, simply by programming computers ("virtual" strong alife). I ask what sort of things these computer-generated organisms are supposed to be (where are they, and what are they made of?). I consider four possible answers to this question: (a) The organisms are abstract complexes of pure information; (b) they are material objects made of bits of computer hardware; (c) they are physical processes going on inside the computer; and (d) they are denizens of an entire artificial world, different from our own, that the programmer creates. I argue that (a) could not be right, that (c) collapses into (b), and that (d) would make strong alife either absurd or uninteresting. Thus, "virtual" strong alife amounts to the claim that, by programming a computer, one can literally bring bits of its hardware to life

C-Sheep: Controlling Entities in a 3D Virtual World as a Tool for Computer Science Education

One of the challenges in teaching computer science in general and computer programming in particular is to maintain the interest of students, who often perceive the subject as difficult and tedious. To this end, we introduce C-Sheep, a mini-language-like system for computer science education, using a state of the art rendering engine, usually found in entertainment systems. The intention is to motivate students to spend more time programming, which can be achieved by providing an enjoyable experience. Computer programming is an essential skill for software developers and as such is always an integral part of every computer science curriculum. However, even if students are pursuing a computer science related degree, it can be very difficult to interest them in the act of computer programming, the writing of software, itself. In the C-Sheep system this is addressed by using the visual gimmickry of modern computer games, which allows programs to provide instant visualisation of algorithms. This visual feedback is invaluable to the understanding of how the algorithm works, and - if there are unintended results - how errors in the program can be debugged. The C-Sheep programming language is a (100% compatible) subset of the ANSI C programming language. Apart from just being a tool for learning the basics of the C programming language, C-Sheep implements the C control structures that are required for teaching the basic computer science principles encountered in structured programming. Unlike other teaching languages which have minimal syntax and which are variable free to provide an environment with minimal complexity, C-Sheep allows the declaration and use of variables. C-Sheep also supports the definition of sub-routines (functions) which can be called recursively. "The Meadow" virtual environment is the virtual world in which entities (in our case sheep) controlled by C-Sheep programs exist. This micro world provides a graphical representation of the algorithms used in the programs controlling the virtual entities. Their position and orientation within the virtual world visualise the current state of the program. "The Meadow" is based on our proprietary "Crossbow" game engine which incorporates a virtual machine for executing CSheep programs. The Crossbow Engine is a compact game engine which is flexible in design and offers a number of features common to more complex engines. The Crossbow Virtual Machine used with C-Sheep in "The Meadow" - an improvement on the ZBL/0 virtual machine - is a module of the Crossbow Engine. The C-Sheep system also provides a counterpart library for C, mirroring the CSheep library functions of the virtual machine. This allows C-Sheep programs to be compiled into an executable using a normal off-the-shelf C/C++ compiler. This executable can then be run from within the native working environment of the operating system. The purpose of this library is to simplify the migration from the educational mini-language to real-world systems by allowing novice programmers to make an easy transition from using the C-Sheep system to using the C programming language