Linear space bootstrap communication schemes

Abstract

We consider a system of n processes with ids not a priori known, that are drawn from a large space, potentially unbounded. How can these n processes communicate to solve a task? We show that n a priori allocated Multi-Writer Multi-Reader (MWMR) registers are both needed and sufficient to solve any read-write wait free solvable task. This contrasts with the existing possible solution borrowed from adaptive algorithms that require Θ (n2 ) MWMR registers. To obtain these results, the paper shows how the processes can non blocking emulate a system of n Single-Writer Multi-Reader (SWMR) registers on top of n MWMR registers. It is impossible to do such an emulation with n - 1 MWMR registers. Furthermore, we want to solve a sequence of tasks (potentially infinite) that are sequentially dependent (processes need the previous task's outputs in order to proceed to the next task). A non blocking emulation might starve a process forever. By doubling the space complexity, using 2n - 1 rather than just n registers, the computation is wait free rather than non blocking. © Springer-Verlag 2013.