This is an Rcpp function calling a n1PDF_gpu function defined
in the global environment, which connects to an interanl ppda
simulated-based LBA density function.
n1PDF_gpu(x, A, b, mean_v, sd_v, t0, n, nthread, gpuid, bw, debug)response time vector
start point variability
threshold
mean drift rate vector
standard deviation of the drift rates
nondecision time
number of simulations
thread number to launch in GPU
which gpu card to use, starting from 0.
kernel bandwidth
debugging?