optimize the bootstrap function.

[brentp]

These changes result in a 4-5X speedup over master.

To test, I set the seed (commented out) and ran the original aFC.py with timings and then the code with these changes. The output is identical.

However the timings for this branch are:

6. Calculating eQTL effect sizes...
     COMPLETED 100 of 30694 = 0.003258 in 260 seconds
     COMPLETED 200 of 30694 = 0.006516 in 112 seconds
     COMPLETED 300 of 30694 = 0.009774 in 114 seconds
     COMPLETED 400 of 30694 = 0.013032 in 111 seconds
     COMPLETED 500 of 30694 = 0.016290 in 106 seconds
     COMPLETED 600 of 30694 = 0.019548 in 106 seconds
     ...

while master shows:

6. Calculating eQTL effect sizes...
     COMPLETED 100 of 30694 = 0.003258 in 724 seconds
     COMPLETED 200 of 30694 = 0.006516 in 559 seconds
     COMPLETED 300 of 30694 = 0.009774 in 608 seconds
     ...

There are further optimizations possible, but I think these are the lowest hanging fruit with the smallest changes.

[brentp]

ping @secastel

[secastel]

Sorry for the delay! Had to find the time to do internal testing and make sure the results are the same. Everything looks good, thanks so much for the fixes!

[brentp]

cheers