BuildBattle reward handler is slow

[katja-hofmann]

Server side evaluation of RewardForStructureCopying is slow. As a result, agents may take several steps after completing a task, leading to unpredictable task success.

Example XML shown below. An action sequence that solves this task is turn -1, move 1, move 1, turn 1, use 1 but this solution fails intermittently (at least when overclocking).

Tested on Malmo-0.21.0 and Malmo-0.30.0.

<?xml version="1.0" ?>
<Mission xmlns="http://ProjectMalmo.microsoft.com" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://ProjectMalmo.microsoft.com Mission.xsd">
    <About>
        <Summary> Build Battle where the task is to copy a built cuboid structure in a defined area. </Summary>
    </About>
    <ModSettings>
        <MsPerTick>1</MsPerTick>
        <PrioritiseOffscreenRendering>true</PrioritiseOffscreenRendering>
    </ModSettings>
    <ServerSection>
        <ServerInitialConditions>
            <Time>
                <StartTime> 1000 </StartTime>
                <AllowPassageOfTime> false </AllowPassageOfTime>
            </Time>
            <Weather>clear</Weather>
            <AllowSpawning> false </AllowSpawning>
        </ServerInitialConditions>
        <ServerHandlers>
            <FlatWorldGenerator forceReset="true" generatorString="0;80;0"/>
            <DrawingDecorator>
                <DrawCuboid type="air" x1="-2" x2="3" y1="0" y2="6" z1="-2" z2="5"/>
                <DrawCuboid type="sea_lantern" x1="-2" x2="3" y1="0" y2="0" z1="-2" z2="5"/>
                <DrawCuboid type="sandstone" x1="0" x2="1" y1="0" y2="0" z1="0" z2="3"/>
                <DrawCuboid type="sea_lantern" x1="-2" x2="3" y1="6" y2="6" z1="-2" z2="5"/>
                <DrawCuboid type="sea_lantern" x1="-2" x2="-2" y1="0" y2="6" z1="-2" z2="5"/>
                <DrawCuboid type="sea_lantern" x1="-2" x2="3" y1="0" y2="6" z1="-2" z2="-2"/>
                <DrawCuboid type="sea_lantern" x1="-2" x2="3" y1="0" y2="6" z1="5" z2="5"/>
                <DrawCuboid type="sea_lantern" x1="3" x2="3" y1="0" y2="6" z1="-2" z2="5"/>
                <DrawBlock type="air" x="0" y="3" z="0"/>
                <DrawBlock type="air" x="0" y="3" z="1"/>
                <DrawBlock type="air" x="0" y="3" z="2"/>
                <DrawBlock type="air" x="0" y="3" z="3"/>
                <DrawBlock type="lapis_block" x="1" y="3" z="0"/>
                <DrawBlock type="lapis_block" x="1" y="0" z="0"/>
                <DrawBlock type="air" x="1" y="3" z="1"/>
                <DrawBlock type="air" x="1" y="3" z="2"/>
                <DrawBlock type="air" x="1" y="3" z="3"/>
                <DrawBlock type="air" x="0" y="1" z="0"/>
                <DrawBlock type="air" x="0" y="1" z="1"/>
                <DrawBlock type="air" x="0" y="1" z="2"/>
                <DrawBlock type="air" x="0" y="1" z="3"/>
                <DrawBlock type="air" x="1" y="1" z="0"/>
                <DrawBlock type="air" x="1" y="1" z="1"/>
                <DrawBlock type="air" x="1" y="1" z="2"/>
                <DrawBlock type="air" x="1" y="1" z="3"/>
            </DrawingDecorator>
            <BuildBattleDecorator>
                <PlayerStructureBounds>
                    <min x="0" y="1" z="0"/>
                    <max x="1" y="1" z="3"/>
                </PlayerStructureBounds>
                <GoalStructureBounds>
                    <min x="0" y="3" z="0"/>
                    <max x="1" y="3" z="3"/>
                </GoalStructureBounds>
                <BlockTypeOnCorrectPlacement type="wool"/>
                <BlockTypeOnIncorrectPlacement type="obsidian"/>
            </BuildBattleDecorator>
            <ServerQuitFromTimeUp description="out_of_time" timeLimitMs="150000"/>
            <ServerQuitWhenAnyAgentFinishes/>
        </ServerHandlers>
    </ServerSection>
    <AgentSection mode="Creative">
        <Name>Builder</Name>
        <AgentStart>
            <Placement pitch="55.0" x="-0.5" y="2" yaw="0.0" z="-0.5"/>
            <Inventory>
                <InventoryBlock quantity="20" slot="0" type="lapis_block"/>
            </Inventory>
        </AgentStart>
        <AgentHandlers>
            <DiscreteMovementCommands/>
            <ObservationFromFullStats/>
            <AgentQuitFromReachingCommandQuota description="Command quota reached." total="100"/>
            <RewardForSendingCommand dimension="0" reward="-1"/>
            <RewardForStructureCopying rewardScale="1" rewardForCompletion="10">
                <RewardDensity>PER_BLOCK</RewardDensity>
                <AddQuitProducer description="Build successful!"/>
            </RewardForStructureCopying>
        </AgentHandlers>
    </AgentSection>
</Mission>