📄 README.md

moonbit-core-affinity

A MoonBit library for managing CPU core affinities to control thread-to-core binding. This library enables precise control over CPU core affinity, allowing you to bind threads to specific cores. It's particularly useful for high-performance applications, real-time systems, and scenarios where you need to optimize CPU cache locality, reduce context switching overhead, or isolate workloads on dedicated cores.

Installation

Add justjavac/core_affinity to your dependencies: ``

bash
moon update
moon add justjavac/core_affinity



## Usage

moonbit
fn main {
  // Get available core IDs
  let core_ids = @core_affinity.get_core_ids()
  println("Available core IDs: \{core_ids}")
  
  // Early return if no cores are available
  if core_ids.length() == 0 {
    println("No available cores found.")
    return
  }
  
  let first_core_id = core_ids[0]
  println("Setting affinity to core: \{first_core_id}")
  
  let success = @core_affinity.set_for_current([first_core_id])
  if not(success) {
    println("Failed to set affinity to core: \{first_core_id}")
    return
  }

  println("Successfully set affinity to core: \{first_core_id}")
}



## Platform Support

| Platform | get_core_ids() | set_for_current() | Implementation |
|----------|----------------|-------------------|----------------|
| Windows | ✅ | ✅ | Win32 API (

GetProcessAffinityMask, SetThreadAffinityMask

) |
| Linux | ✅ | ✅ | POSIX (

schedgetaffinity, schedsetaffinity

) |
| macOS | ✅ | ✅ | BSD/Darwin thread affinity APIs |
| Other Unix | ⚠️ | ⚠️ | Limited support, platform-dependent |

- ✅ = Full support
- ⚠️ = Limited/platform-dependent support

## Examples

### Basic Usage

moonbit
fn main {
  let cores = @core_affinity.get_core_ids()
  println("Available cores: \{cores}")
}



### Single Core Binding

moonbit
fn bind_to_first_core() -> Bool {
  let cores = @core_affinity.get_core_ids()
  if cores.length() > 0 {
    @core_affinity.set_for_current([cores[0]])
  } else {
    false
  }
}



### Multi-Core Binding

moonbit
fn bind_to_even_cores() -> Bool {
  let cores = @core_affinity.get_core_ids()
  let even_cores = []
  
  for core in cores {
    if core % 2 == 0 {
      even_cores.push(core)
    }
  }
  
  if even_cores.length() > 0 {
    @core_affinity.set_for_current(even_cores)
  } else {
    false
  }
}



## Examples

You can find example usage in the

example/

 directory:

bash
moon run --target native -C example .

License

MIT License - see LICENSE file for details.