Creating and configuring a new instance would be cleaner if a builder pattern is followed.

I wonder why 0 is too small a value in the implementation?

Can't histogram be generic and receive any type instead of being hardcoded to accept only u64?

The project maintainer explicitly asked for this issue to be opened.

TL;DR the Rust ecosystem is largely Apache-2.0. Being available under that
license is good for interoperation. The MIT license as an add-on can be nice
for GPLv2 projects to use your code.

Why?

The MIT license requires reproducing countless copies of the same copyright
header with different names in the copyright field, for every MIT library in
use. The Apache license does not have this drawback. However, this is not the
primary motivation for me creating these issues. The Apache license also has
protections from patent trolls and an explicit contribution licensing clause.
However, the Apache license is incompatible with GPLv2. This is why Rust is
dual-licensed as MIT/Apache (the "primary" license being Apache, MIT only for
GPLv2 compat), and doing so would be wise for this project. This also makes
this crate suitable for inclusion and unrestricted sharing in the Rust
standard distribution and other projects using dual MIT/Apache, such as my
personal ulterior motive, the Robigalia project.

Some ask, "Does this really apply to binary redistributions? Does MIT really
require reproducing the whole thing?" I'm not a lawyer, and I can't give legal
advice, but some Google Android apps include open source attributions using
this interpretation. Others also agree with
it.
But, again, the copyright notice redistribution is not the primary motivation
for the dual-licensing. It's stronger protections to licensees and better
interoperation with the wider Rust ecosystem.

How?

To do this, get explicit approval from each contributor of copyrightable work
(as not all contributions qualify for copyright, due to not being a "creative
work", e.g. a typo fix) and then add the following to your README:

## License

Licensed under either of

 * Apache License, Version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0)
 * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)

at your option.

### Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted
for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any
additional terms or conditions.

and in your license headers, if you have them, use the following boilerplate
(based on that used in Rust):

// Copyright 2016 histogram Developers
//
// Licensed under the Apache License, Version 2.0, <LICENSE-APACHE or
// http://apache.org/licenses/LICENSE-2.0> or the MIT license <LICENSE-MIT or
// http://opensource.org/licenses/MIT>, at your option. This file may not be
// copied, modified, or distributed except according to those terms.

It's commonly asked whether license headers are required. I'm not comfortable
making an official recommendation either way, but the Apache license
recommends it in their appendix on how to use the license.

Be sure to add the relevant LICENSE-{MIT,APACHE} files. You can copy these
from the Rust repo for a plain-text
version.

And don't forget to update the license metadata in your Cargo.toml to:

license = "MIT OR Apache-2.0"

I'll be going through projects which agree to be relicensed and have approval
by the necessary contributors and doing this changes, so feel free to leave
the heavy lifting to me!

Contributor checkoff

To agree to relicensing, comment with :

I license past and future contributions under the dual MIT/Apache-2.0 license, allowing licensees to chose either at their option.

Or, if you're a contributor, you can check the box in this repo next to your
name. My scripts will pick this exact phrase up and check your checkbox, but
I'll come through and manually review this issue later as well.

• @brayniac

Histogram buckets should have accessor functions, not direct access to fields

Does it support bin count?

I just got the request for a non-uniform histogram

posix4e/rust-metrics#81

I assume people responding to the HDRhistogram stuff. What do we think?

Would there be any argument against having HistogramConfig's methods return Self instead of &mut Self? This would allow a very nice:

let h = Histogram::configured(
              HistogramConfig::new()
              .max_value(100)
              .precision(1));

Alternatively, I could imagine the following additional methods (while keeping the old ones as their are):

let h = Histogram::configured(
              HistogramConfig::new()
              .with_max_value(100)
              .with_precision(1));

If one of these would be ok from your side, I could submit a PR.

I understand that all the values in the histogram are u64 - that makes sense - but why are the statistics all converted to u64 as well?

This isn't such a problem for percentiles (as they at least have the range of the original inputs) - but for standard deviation, it produces heavily truncated results if the input doesn't have a lot of variation.

It would be very nice to have f64 versions of these functions - I note that most of them are internally calculated as f64 and then converted to u64 on return.

(Actually I just discovered stddev is even worse! stdvar produces a f64 value, then truncates it to u64. And then stddev converts it back to a f64, takes the square-root, and truncates to u64 again)

I'm trying to write a metrics library http://github.com/posix4e/rust-metrics which uses this histogram package . I want to make a reporter for prometheus but I don't know how to convert your histogram to

message Quantile {
  optional double quantile = 1;
  optional double value    = 2;
}

message Summary {
  optional uint64   sample_count = 1;
  optional double   sample_sum   = 2;
  repeated Quantile quantile     = 3;
}

message Untyped {
  optional double value = 1;
}

message Histogram {
  optional uint64 sample_count = 1;
  optional double sample_sum   = 2;
  repeated Bucket bucket       = 3; // Ordered in increasing order of upper_bound, +Inf bucket is optional.
}

message Bucket {
  optional uint64 cumulative_count = 1; // Cumulative in increasing order.
  optional double upper_bound = 2;      // Inclusive.
}

Could this be based on the id?

Would it be possible to add these statistics? They are generally more stable than mean and stddev...

Spawned from discussion on #1

Enhancements

• add mean/stdvar/stddev to Histogram
• min/max as convenience functions for p0 p100

Hello, this is more of a question rather than an issue:

I'm not understanding why in Histogram::configured we validate buckets_total * mem::size_of::<HistogramBucket>(). Isn't the histogram's data stored as a u64 per bucket (while a HistogramBucket has 24 bytes?) What is the exact idea behind config.max_memory?

Many thanks in advance, P.