## Embed new cells in an already existing space

I have implemented an RcppParalle and Rcpp version of Mann–Whitney U test with continuity correction, that using 6 threads was about **100X faster then native R function** and **5X faster then corresponding serial C++ function**. Test were performed using i7 with 6 cores.

The implemented C++ Mann–Whitney U test correspond to the R command wilcox.test(x,y,alternative = “two.sided”, paired = F,exact = F,correct = T).

Below the code used to generate the above table.

```
set.seed(0)
ngenes = 3000;
ncells = 5000;
expr = matrix( rnorm(ngenes*ncells,mean=0,sd=1), ngenes, ncells)
# Benchmarks
RcppParallel::setThreadOptions(numThreads = 6)
ix1 = 1:round(ncells/2)
ix2 = (round(ncells/2)+1):ncells
res <- benchmark(apply(X = expr, MARGIN = 1, FUN = function(x,i1=ix1,i2=ix2) wilcox.test(x = x[i1],y = x[i2],alternative = "two.sided", paired = F,exact = F,correct = T)),
gficf:::rcpp_WMU_test(M = expr,idx1 = ix1,idx2 = ix2),
gficf:::rcpp_parallel_WMU_test(matX = expr[,ix1],matY = expr[,ix2],printOutput = F),
replications=3,
order="elapsed"
)
print(res[,c("test","elapsed","relative")])
```

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