This article introduces GraphCL, an automated system for seamlessly mapping multi-kernel applications to multiple computing devices. GraphCL consists of a C ++ API and a runtime that abstracts and simplifies the execution of multi-kernel applications on heterogeneous platforms across multiple devices. The GraphCL approach has three steps. First, the application designer provides a kernel graph. In the second phase, GraphCL computes the execution schedule. After the schedule has been computed, the runtime uses the execution schedule to enqueue in parallel the processing for all system processors. GraphCL takes the kernel dependencies and the processor performance differences into account during the schedule calculation process. By deciding on the schedule, GraphCL transparently manages the order of execution and data transfers for each processor. On two asymmetric workstations, GraphCL achieves an average acceleration of 1.8x compared to the fastest device. GraphCL achieves also for the set of multi-kernel benchmarks an average 24.5% energy reduction compared to the lazy partition heuristic, that uses all the system processors without considering their power usage.