Optimising CP2K for the Intel Xeon Phi

CP2K is an important European program for atomistic simulation for many users of the PRACE Research Infrastructure as well as national and local compute resources. In the context of a PRACE Preparatory Access Type C project, we have parallelised several routines in CP2K to allow the code to gain better performance on the Intel Xeon Phi for a materials science application. We have obtained a 50% speedup in the maximum performance of the code on the Xeon Phi, but have not been able to demonstrate better performance than running the same calculation on a Sandy Bridge 16-core CPU node. We present details of the developments made to CP2K, and discuss several lessons, which will be of wider interest to developers considering porting their codes to Xeon Phi.