Revisiting randomized parallel load balancing algorithms

  • Authors:
  • Guy Even;Moti Medina

  • Affiliations:
  • School of Electrical Engineering, Tel-Aviv Univ., Tel-Aviv, Israel;School of Electrical Engineering, Tel-Aviv Univ., Tel-Aviv, Israel

  • Venue:
  • SIROCCO'09 Proceedings of the 16th international conference on Structural Information and Communication Complexity
  • Year:
  • 2009

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Abstract

We deal with the well studied allocation problem of assigning n balls to n bins so that the maximum number of balls assigned to the same bin is minimized. We focus on randomized, constant-round, distributed, asynchronous algorithms for this problem. Adler et al. [1] presented lower bounds and upper bounds for this problem. A similar lower bound appears in Berenbrink et al. [2]. The lower bound is based on a topological assumption. Our first contribution is the observation that the topological assumption does not hold for two algorithms presented by Adler et al. [1]. We amend this situation by presenting direct proofs of the lower bound for these two algorithms. We present an algorithm in which a ball that was not allocated in the first round retries with a new choice in the second round. We present tight bounds on the maximum load obtained by our algorithm. The analysis is based on analyzing the expectation and transforming it to a bound with high probability using martingale tail inequalities. Finally, we present a 3-round heuristic with a single synchronization point. We conducted experiments that demonstrate its advantage over parallel algorithms for 106≤n≤108 balls and bins. In fact, the obtained maximum load meets the best results for sequential algorithms.