479-atomic-race.yaml

# This scenario is specially engineered to almost guarantee a crash
# due to a race condition in short order.
#
#   - The steps per tick is set to 1, so robots are interrupted after
#     every single step, making bugs due to bad interleaving much more
#     probable.
#   - A `weed` entity is used which grows very quickly
#   - `harvest` is used, which causes more weeds to grow in the same spot
#   - A crash happens when the planter robot tests for the presence of a weed
#     and doesn't find one, but then is interrupted and a new weed grows;
#     then the planter robot crashes when it tries to place a weed.
#   - The harvesting robot waits a random number of ticks between 1-4 each
#     time, to give the planting robot time to run into the race condition.
#
# This may work slightly less well once we implement #502, but I think it should
# still work.

version: 1
name: Grab/harvest/place (with race)
description: |
  Make sure we can cause a robot to crash due to a race condition, in order to
  know that atomic blocks are doing their job.
  https://github.com/swarm-game/swarm/issues/479
stepsPerTick: 1
creative: true
objectives:
  - condition: |
      try {
        p <- robotNamed "planter";
        as p {has "Win"}
      } { return false }
solution: |
  def forever = \c. force c ; forever c end
  def tryharvest =
    b <- ishere "weed";
    if b {harvest; n <- random 4; wait n} {}
  end;
  forever {tryharvest}
robots:
  - name: base
    loc: [0,0]
    dir: [1,0]
    devices:
      - logger
      - harvester
    inventory:
      - [1, lambda]
  - name: planter
    loc: [0,0]
    dir: [1,0]
    devices:
      - logger
      - grabber
    inventory:
      - [25, weed]
    program: |
      def forever = \c. force c ; forever c end
      def tryplant =
        b <- ishere "weed";
        if b {} {place "weed"}
      end;
      forever {try {tryplant} {create "Win"}}
entities:
  - name: weed
    display:
      attr: plant
      char: 'W'
    description:
    - A fast-growing weed.
    properties: [known, portable, growable]
    growth: [1,2]
  - name: Win
    display:
      attr: device
      char: 'W'
    description:
      - You win!
    properties: [known, portable]
world:
  palette:
    '.': [grass]
  upperleft: [0,0]
  map: |
    .