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#ifndef _BLASR_STAT_UTILS_IMPL_HPP_
#define _BLASR_STAT_UTILS_IMPL_HPP_
#include <ctime>
#include <vector>
inline int Choose(int a, int b)
{
// A quick choose for small values.
assert(a >= b);
if (a < FactorialTableLength and b < FactorialTableLength) {
return (FactorialTable[a] / (FactorialTable[b] * FactorialTable[a - b]));
} else {
//
// Less quick choose for numerically stable values.
//
unsigned long al = a, bl = b, fact = 0;
fact = al;
//
// The full value of b! must be able to be computed.
//
if (b >= FactorialTableLength) {
return 0;
}
while (al > bl) {
--al;
if (ULONG_MAX / al < fact) {
// there is overflow in the computation of a!/(a-b)!
return 0;
} else {
fact = fact * al;
}
}
return fact / FactorialTable[b];
}
}
template <typename T>
void MeanVar(std::vector<T> &values, float &mean, float &var)
{
T sum = 0;
T sumsq = 0;
size_t i;
if (values.size() == 0) {
mean = 0;
var = 0;
return;
}
for (i = 0; i < values.size(); i++) {
sum += values[i];
sumsq += values[i] * values[i];
}
mean = (1.0 * sum) / values.size();
var = sumsq / values.size() - (mean * mean);
}
#endif
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