  Collaborative Edge Computing (CEC) is a new edge computing paradigm that
enables neighboring edge servers to share computational resources with each
other. Although CEC can enhance the utilization of computational resources, it
still suffers from resource waste. The primary reason is that end-users from
the same area are likely to offload similar tasks to edge servers, thereby
leading to duplicate computations. To improve system efficiency, the
computation results of previously executed tasks can be cached and then reused
by subsequent tasks. However, most existing computation reuse algorithms only
consider one edge server, which significantly limits the effectiveness of
computation reuse. To address this issue, this paper applies computation reuse
in CEC networks to exploit the collaboration among edge servers. We formulate
an optimization problem that aims to minimize the overall task response time
and decompose it into a caching subproblem and a scheduling subproblem. By
analyzing the properties of optimal solutions, we show that the optimal caching
decisions can be efficiently searched using the bisection method. For the
scheduling subproblem, we utilize projected gradient descent and backtracking
to find a local minimum. Numerical results show that our algorithm
significantly reduces the response time in various situations.
