A collection of histogram data structures for Rust, providing standard, atomic, and sparse variants. Like HDRHistogram, values are stored in quantized buckets, but the bucket construction and indexing algorithm are modified for fast increments and lookups.

cargo add histogram

use histogram::Histogram;

// Create a histogram with grouping power 7 and max value power 64.
let mut histogram = Histogram::new(7, 64).unwrap();

// Record some values.
for i in 1..=100 {
    histogram.increment(i).unwrap();
}

// Query percentiles using the 0.0..=1.0 scale.
let median = histogram.percentile(0.5).unwrap().unwrap();
let p99 = histogram.percentile(0.99).unwrap().unwrap();
// percentile() returns Result<Option<Bucket>, Error>
// outer unwrap: percentile value is valid
// inner unwrap: histogram is non-empty

println!("median: {}", median.end());
println!("p99: {}", p99.end());

• Histogram -- Standard histogram with plain 64-bit counters. Best for single-threaded use.
• AtomicHistogram -- Uses atomic 64-bit counters, allowing concurrent recording from multiple threads. Take a snapshot via load() or drain() to query percentiles.
• SparseHistogram -- Columnar representation that only stores non-zero buckets. Ideal for serialization and storage when most buckets are empty.

• serde -- Enables Serialize and Deserialize for histogram types.
• schemars -- Enables JSON Schema generation (implies serde).

• API Documentation
• Crates.io
• Repository

Licensed under either of Apache License, Version 2.0 or MIT license at your option.