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#[derive(Debug, Clone)]
pub struct Histogram {
count: u64,
bounds: Vec<f64>,
buckets: Vec<u64>,
sum: f64,
}
impl Histogram {
pub fn new(bounds: &[f64]) -> Option<Histogram> {
if bounds.is_empty() {
return None;
}
let buckets = vec![0u64; bounds.len()];
Some(Histogram {
count: 0,
bounds: Vec::from(bounds),
buckets,
sum: 0.0,
})
}
pub fn sum(&self) -> f64 {
self.sum
}
pub fn count(&self) -> u64 {
self.count
}
pub fn buckets(&self) -> Vec<(f64, u64)> {
self.bounds
.iter()
.cloned()
.zip(self.buckets.iter().cloned())
.collect()
}
pub fn record(&mut self, sample: f64) {
self.sum += sample;
self.count += 1;
for (idx, bucket) in self.bounds.iter().enumerate() {
if sample <= *bucket {
self.buckets[idx] += 1;
}
}
}
pub fn record_many<'a, S>(&mut self, samples: S)
where
S: IntoIterator<Item = &'a f64> + 'a,
{
let mut bucketed = vec![0u64; self.buckets.len()];
let mut sum = 0.0;
let mut count = 0;
for sample in samples.into_iter() {
sum += *sample;
count += 1;
for (idx, bucket) in self.bounds.iter().enumerate() {
if sample <= bucket {
bucketed[idx] += 1;
break;
}
}
}
if bucketed.len() >= 2 {
for idx in 0..(bucketed.len() - 1) {
bucketed[idx + 1] += bucketed[idx];
}
}
for (idx, local) in bucketed.iter().enumerate() {
self.buckets[idx] += local;
}
self.sum += sum;
self.count += count;
}
}
#[cfg(test)]
mod tests {
use super::Histogram;
#[test]
fn test_histogram() {
let histogram = Histogram::new(&[]);
assert!(histogram.is_none());
let buckets = &[10.0, 25.0, 100.0];
let values = vec![3.0, 2.0, 6.0, 12.0, 56.0, 82.0, 202.0, 100.0, 29.0];
let mut histogram = Histogram::new(buckets).expect("histogram should have been created");
histogram.record_many(&values);
histogram.record(89.0);
let result = histogram.buckets();
assert_eq!(result.len(), 3);
let (_, first) = result[0];
assert_eq!(first, 3);
let (_, second) = result[1];
assert_eq!(second, 4);
let (_, third) = result[2];
assert_eq!(third, 9);
assert_eq!(histogram.count(), values.len() as u64 + 1);
assert_eq!(histogram.sum(), 581.0);
}
}