instruments.go
func (r *Reservoir) Update(v float64) {
	r.m.Lock()
	r.hist.Add(v)
	r.m.Unlock()
}
func (r *Reservoir) Update(v float64) {
	r.m.Lock()
	r.hist.Add(v)
	r.m.Unlock()
}
func ( r * Reservoir ) Update ( v float64 ) { r . m . Lock ( ) r . hist . Add ( v ) r . m . Unlock ( ) }
// Update fills the sample randomly with given value,
// for reference, see: http://en.wikipedia.org/wiki/Reservoir_sampling
Update fills the sample randomly with given value for reference see : http : // en . wikipedia . org / wiki / Reservoir_sampling