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Multiple Runtimes & Modes ​

Comparison table ​

Pass --runtime more than once and every bench runs under each runtime, rendered as a comparison table normalized to the fastest:

bash
asb run --runtime node --runtime wasmtime --runtime wasmer
text
runtime comparison (point estimates, fastest = 1.00×)

fib(20)
  node      45.97 µs  1.00×
  wasmtime  61.40 µs  1.34×
  wasmer    63.10 µs  1.37×

The same effect is available in config via a runOptions.runtime list (see below), which is the better home for a comparison you run often.

In --json mode the comparison table is suppressed — only the JSON document is written to stdout.

Modes ​

A mode is a named partial-config overlay applied with --mode <name>. Objects merge one level deep; scalars and arrays replace. Precedence is:

text
defaults < config < mode < CLI flags
json
{
  "settings": { "warmupTime": 250, "measurementTime": 500 },
  "modes": {
    "full":      { "settings": { "warmupTime": 3000, "measurementTime": 5000 } },
    "wasmtime":  { "runtime": "wasmtime" },
    "compare":   {
      "runOptions": {
        "runtime": ["node", "wasmtime", "wasmer", { "cmd": "wazero run <env:-env> <file>", "name": "wazero" }]
      }
    }
  }
}
bash
asb run --mode full       # criterion-style long run
asb run --mode compare    # node + wasmtime + wasmer + wazero, one table

A runOptions.runtime list mixes plain strings (a named runtime or a command template) and {cmd, name} objects. --mode works on run, build, profile, watch, compare, doctor, and clean.

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