6 research outputs found
OBDD(Join) Proofs Cannot Be Balanced
We study OBDD-based propositional proof systems introduced in 2004 by Atserias, Kolaitis, and Vardi that prove the unsatisfiability of a CNF formula by deduction of an identically false OBDD from OBDDs representing clauses of the initial formula. We consider a proof system OBDD(?) that uses only the conjunction (join) rule and a proof system OBDD(?, reordering) (introduced in 2017 by Itsykson, Knop, Romashchenko, and Sokolov) that uses the conjunction (join) rule and the rule that allows changing the order of variables in OBDD.
We study whether these systems can be balanced i.e. every refutation of size S can be reassembled into a refutation of depth O(log S) with at most a polynomial-size increase. We construct a family of unsatisfiable CNF formulas F_n such that F_n has a polynomial-size tree-like OBDD(?) refutation of depth poly(n) and for arbitrary OBDD(?, reordering) refutation ? of F_n for every ? ? (0,1) the following trade-off holds: either the size of ? is 2^?(n^?) or the depth of ? is ?(n^{1-?}). As a corollary of the trade-offs, we get that OBDD(?) and OBDD(?, reordering) proofs cannot be balanced
Fast Simulation of Programmable Network Forwarding Plane Devices
With the evolution of the Internet, the processing of packets at the routers while providing
flexibility in deploying new protocols and services at the same time has become a major concern.
Programmable forwarding elements with high processing capability have emerged as a solution.
But the main challenge is to find the optimal hardware architecture while taking into account
constraints such as different packet processing functions, task scheduling options, electrical
power consumption and providing quality-of-service (QoS) guarantees. Therefore, it is essential
to investigate methods that help in identifying limitations and bottlenecks before physical
fabrication. Having an appropriate model provides designers a progressive path to narrow the
design space and establish credible and feasible alternatives before deciding on an
implementation.
In this thesis, we propose a flexible and fast instruction accurate host-compiled simulator to
make it possible to explore wide ranges of architectures and application scenarios to find the
optimal configuration that meets given performance, throughput and latency for programmable
forwarding elements. Application developers can use the simulator as a virtual prototype to
simulate and debug their applications before hardware availability. Moreover, forwarding device
architects can use simulator to evaluate the trade-offs between different hardware/software
design decisions