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```````pony linenums="1"
struct RuntimeOptions
  """
  Pony struct for the Pony runtime options C struct that can be used to
  override the Pony runtime defaults via code compiled into the program.

  The way this is done is by adding the following function to your `Main` actor:

  ```
    fun @runtime_override_defaults(rto: RuntimeOptions) =>
  ```

  and then overriding the fields of `rto` (the `RuntimeOptions` instance) as
  needed.

  NOTE: Command line arguments still any values set via
        `@runtime_override_defaults`.


  The following example overrides the `--ponyhelp` argument to default it to
  `true` instead of `false` causing the compiled program to always display
  the Pony runtime help:

  ```
  actor Main
    new create(env: Env) =>
      env.out.print("Hello, world.")

    fun @runtime_override_defaults(rto: RuntimeOptions) =>
      rto.ponyhelp = true
  ```
  """

/* NOTE: if you change any of the field docstrings, update `options.h` in
 *       the runtime to keep them in sync.
 */

  var ponymaxthreads: U32 = 0
    """
    Use N scheduler threads. Defaults to the number of cores (not hyperthreads)
    available.
    This can't be larger than the number of cores available.
    """

  var ponyminthreads: U32 = 0
    """
    Minimum number of active scheduler threads allowed.
    Defaults to 0, meaning that all scheduler threads are allowed to be
    suspended when no work is available.
    This can't be larger than --ponymaxthreads if provided, or the physical
    cores available.
    """

  var ponynoscale: Bool = false
    """
    Don't scale down the scheduler threads.
    See --ponymaxthreads on how to specify the number of threads explicitly.
    Can't be used with --ponyminthreads.
    """

  var ponysuspendthreshold: U32 = 0
    """
    Amount of idle time before a scheduler thread suspends itself to minimize
    resource consumption (max 1000 ms, min 1 ms).
    Defaults to 1 ms.
    """

  var ponycdinterval: U32 = 100
    """
    Run cycle detection every N ms (max 1000 ms, min 10 ms).
    Defaults to 100 ms.
    """

  var ponygcinitial: USize = 14
    """
    Defer garbage collection until an actor is using at least 2^N bytes.
    Defaults to 2^14.
    """

  var ponygcfactor: F64 = 2.0
    """
    After GC, an actor will next be GC'd at a heap memory usage N times its
    current value. This is a floating point value. Defaults to 2.0.
    """

  var ponynoyield: Bool = false
    """
    Do not yield the CPU when no work is available.
    """

  var ponynoblock: Bool = false
    """
    Do not send block messages to the cycle detector. Setting this to true will disable the cycle detector.
    """

  var ponypin: Bool = false
    """
    Pin scheduler threads to CPU cores. The ASIO thread can also be pinned if
    `--ponypinasio` is set.
    """

  var ponypinasio: Bool = false
    """
    Pin the ASIO thread to a CPU the way scheduler threads are pinned to CPUs.
    Requires `--ponypin` to be set to have any effect.
    """

  var ponypinpinnedactorthread: Bool = false
    """
    Pin the pinned actor thread to a CPU the way scheduler threads are pinned to CPUs.
    Requires `--ponypin` to be set to have any effect.
    """

  var ponyprintstatsinterval: U32 = -1
    """
    Print actor stats before an actor is destroyed and print scheduler stats
    every X seconds. Defaults to -1 (never).
    """

  var ponyversion: Bool = false
    """
    Print the version of the compiler and exit.
    """

  var ponyhelp: Bool = false
    """
    Print the runtime usage options and exit.
    """

  var ponymemoryprofile: U32 = 0
    """
    Trade the allocator's resident memory against throughput on a scale from 1
    to 10: 1 holds little freed memory for reuse and returns the rest to the
    operating system quickly for the smallest footprint, 10 holds the most for
    the most throughput. 0, the default,
    leaves rung 3 in place -- the scale has little room below it for less memory
    and much more above it for throughput, so rung 3 sits low on it. A value
    outside 1 to 10 is rejected at startup.

    ```
    rto.ponymemoryprofile = 8
    ```

    Only the arena allocator acts on it; a program built with pool_classic
    ignores it.
    """

```````