This function can be used to carry our permutation
  resampling inference with GPUs. Currently the function supports six test
  statistics: the t and Wilcoxon tests, for two-sample problems,
  the Pearson and Spearman statistics, for non-censored continuous
  outcomes, and the Cox score and rank score tests (Jung et al, 2005), for
  right-censored time-to-event outcomes.