Hårek Haugerud

Measuring system normality

A comparative analysis of transaction time-series is made, for light to moderately loaded hosts, motivated by the problem of anomaly detection in computers. Criteria for measuring the statistical state of hosts are examined. Applying a scaling transformation to the measured data, it is found that the distribution of fluctuations about the mean is closely approximated by a steady-state, maximum-entropy distribution, modulated by a periodic variation. The shape of the distribution, under these conditions, depends on the dimensionless ratio of the daily/weekly periodicity and the correlation length of the data. These values are persistent or even invariant. We investigate the limits of these conclusions, and how they might be applied in anomaly detection.

A more accurate analysis of Bose-Einstein condensation in harmonic traps

Abstract Using the Euler-Maclaurin summation we calculate analytically the internal energy for non-interacting bosons confined within a harmonic oscillator potential. The specific heat shows a sharp λ-like peak indicating a condensation into the ground state at a well-defined transition temperature. Full agreement is obtained with direct numerical calculation of the same quantities. When the number of trapped particles is very large and at temperatures near and above the transition temperature, the results also agree with previous approximate calculations. At extremely low temperatures both the specific heat and the number of particles excited from the condensate are exponentially suppressed.

IncludeOS: A Minimal, Resource Efficient Unikernel for Cloud Services

The emergence of cloud computing as a ubiquitous platform for elastically scaling services has generated need and opportunity for new types of operating systems. A service that needs to be both elastic and resource efficient needs A) highly specialized components, and B) to run with minimal resource overhead. Classical general purpose operating systems designed for extensive hardware support are by design far from meeting these requirements. In this paper we present IncludeOS, a single tasking library operating system for cloud services, written from scratch in C++. Key features include: extremely small disk-and memory footprint, efficient asynchronous I/O, OS-library where only what your service needs gets included, and only one device driver by default (virtio). As a test case a bootable disk image consisting of a simple DNS server with OS included is shown to require only 158 kb of disk space and to require 5-20% less CPU-time, depending on hardware, compared to the same binary running on Linux.

Exact diagonalization of the Hamiltonian for trapped interacting bosons in lower dimensions

We consider systems of a small number of interacting bosons confined to harmonic potentials in one and two dimensions. By exact numerical diagonalization of the many-body Hamiltonian we determine the low-lying excitation energies and the ground-state energy and density profile. We discuss the dependence of these quantities on both interaction strength

Maximizing Hypervisor Scalability Using Minimal Virtual Machines

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From microscopic description to statistical mechanics of CuO chain fragments in high-Tc superconductors REBa2Cu3O6+x

and particle number

Thermodynamics of a Weakly Interacting Bose–Einstein Gas

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The role of Cu−O chain fragments in the REBa2Cu3O6+x high-Tc superconductors

. The ground-state properties are compared to the predictions of the Gross-Pitaevskii equation, and the agreement is surprisingly good even for relatively low particle numbers. We also calculate the specific heat based on the obtained energy spectra.

Interacting holes in CuO cyclic chains

The smallest instance offered by Amazon EC2 comes with 615MB memory and a 7.9GB disk image. While small by todays standards, embedded web servers with memory footprints well under 100kB, indicate that there is much to be saved. In this work we investigate how large VM-populations the open Stack hyper visor can be made to sustain, by tuning it for scalability and minimizing virtual machine images. Request-driven Qemu images of 512 byte are written in assembly, and more than 110 000 such instances are successfully booted on a 48 core host, before memory is exhausted. Other factors are shown to dramatically improve scalability, to the point where 10 000 virtual machines consume no more than 2.06% of the hyper visor CPU.

Towards a Hybrid Cloud Platform Using Apache Mesos

Abstract The oxygen deficient CuO x planes of the high- T c superconductors REBa 2 Cu 3 O 6+ x (RE denotes a rare-earth atom or yttrium) are studied. Starting from the Emery model for the CuO chain fragments, an extended ASYNNNI model is proposed to describe the statistical mechanics of the CuO x planes. The model is analysed by using Monte Carlo techniques, computing especially the charge transfer to the CuO 2 planes regulating the high- T c superconductivity, and the concentration of differently coordinated Cu ions. Results are compared to experimental data for various RE cases.