CSV Output

NOTE: The CSV output is in the process of being deprecated. For machine-readable output, cargo-criterion's --message-format=json option is recommended instead - see External Tools. CSV output will become an optional feature in Criterion.rs 0.4.0.

Criterion.rs saves its measurements in several files, as shown below:

├── base/
│  ├── raw.csv
│  ├── estimates.json
│  ├── sample.json
│  └── tukey.json
├── change/
│  └── estimates.json
├── new/
│  ├── raw.csv
│  ├── estimates.json
│  ├── sample.json
│  └── tukey.json

The JSON files are all considered private implementation details of Criterion.rs, and their structure may change at any time without warning.

However, there is a need for some sort of stable and machine-readable output to enable projects like lolbench to keep historical data or perform additional analysis on the measurements. For this reason, Criterion.rs also writes the raw.csv file. The format of this file is expected to remain stable between different versions of Criterion.rs, so this file is suitable for external tools to depend on.

The format of raw.csv is as follows:


This data was taken with this benchmark code:

fn main() {
fn compare_fibonaccis(c: &mut Criterion) {
    let mut group = c.benchmark_group("Fibonacci");
    group.bench_with_input("Recursive", 20, |b, i| b.iter(|| fibonacci_slow(*i)));
    group.bench_with_input("Iterative", 20, |b, i| b.iter(|| fibonacci_fast(*i)));

raw.csv contains the following columns:

  • group - This corresponds to the function group name, in this case "Fibonacci" as seen in the code above. This is the parameter given to the Criterion::bench functions.
  • function - This corresponds to the function name, in this case "Iterative". When comparing multiple functions, each function is given a different name. Otherwise, this will be the empty string.
  • value - This is the parameter passed to the benchmarked function when using parameterized benchmarks. In this case, there is no parameter so the value is the empty string.
  • throughput_num - This is the numeric value of the Throughput configured on the benchmark (if any)
  • throughput_type - "bytes" or "elements", corresponding to the variant of the Throughput configured on the benchmark (if any)
  • iteration_count - The number of times the benchmark was iterated for this sample.
  • sample_measured_value - The value of the measurement for this sample. Note that this is the measured value for the whole sample, not the time-per-iteration (see Analysis Process for more detail). To calculate the time-per-iteration, use sample_measured_value/iteration_count.
  • unit - a string representing the unit for the measured value. For the default WallTime measurement this will be "ns", for nanoseconds.

As you can see, this is the raw measurements taken by the Criterion.rs benchmark process. There is one record for each sample, and one file for each benchmark.

The results of Criterion.rs' analysis of these measurements are not currently available in machine-readable form. If you need access to this information, please raise an issue describing your use case.