A Generic Checkpoint-Restart Mechanism for Virtual Machines

It is common today to deploy complex software inside a virtual machine (VM). Snapshots provide rapid deployment, migration between hosts, dependability (fault tolerance), and security (insulating a guest VM from the host). Yet, for each virtual machine, the code for snapshots is laboriously developed on a per-VM basis. This work demonstrates a generic checkpoint-restart mechanism for virtual machines. The mechanism is based on a plugin on top of an unmodified user-space checkpoint-restart package, DMTCP. Checkpoint-restart is demonstrated for three virtual machines: Lguest, user-space QEMU, and KVM/QEMU. The plugins for Lguest and KVM/QEMU require just 200 lines of code. The Lguest kernel driver API is augmented by 40 lines of code. DMTCP checkpoints user-space QEMU without any new code. KVM/QEMU, user-space QEMU, and DMTCP need no modification. The design benefits from other DMTCP features and plugins. Experiments demonstrate checkpoint and restart in 0.2 seconds using forked checkpointing, mmap-based fast-restart, and incremental Btrfs-based snapshots

Fairly Allocating Goods in Parallel

We initiate the study of parallel algorithms for fairly allocating indivisible goods among agents with additive preferences. We give fast parallel algorithms for various fundamental problems, such as finding a Pareto Optimal and EF1 allocation under restricted additive valuations, finding an EF1 allocation for up to three agents, and finding an envy-free allocation with subsidies. On the flip side, we show that fast parallel algorithms are unlikely to exist (formally, $CC$-hard) for the problem of computing Round-Robin EF1 allocations

Analytical Stellar Models of Neutron Stars in Teleparallel Gravity

In this paper, we developed three analytical models and obtained a new class of solutions describing compact stellar structures using the theory of teleparallel gravity. We consider the general anisotropic nature of stellar configurations and solve teleparallel gravity equations. In order to thoroughly analyze the various parameters of the stars, we developed three models by choosing various physically acceptable forms of metric potential $e^{d(r)}$ and radial pressure $p_r(r)$. We also analyze the impact of teleparallel gravity's parameters $\beta$ and $\beta_1$ on the description of the stellar structures. We calculated model parameters such that models describing various observed neutron stars obey all physical conditions to be potentially stable and causal. By analyzing the impact of various parameters of teleparallel gravity on the description of anisotropic stellar structures, we found that three models developed in this paper can describe anisotropic neutron stars ranging from low density to high density. Finally, we obtain a quadratic Equation of State for each model describing various neutron stars, which can be utilized to find compositions of the stellar structures. It is very useful to find models that can exhibit quadratic EOS, since material compositions of real neutron stars and strange stars are found to exhibit quadratic EOS by various authors. Non linear $f(T)$ model gives high deviation of EOS from quadratic behaviour, thus, in this paper we work with linear $f(T)$ function by using diagonal tetrad to model realistic compact stars.Comment: made equations more readable and implemented some changes suggested by reviewer