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POstd::map Access Speed Is Too Slow?
 

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  1. POstd::map Access Speed Is Too Slow?
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    <p>I have recently been implementing an Entity-component system for my game engine. Every entity keeps a map of components like that :</p> <p>Component.h</p> <pre><code>enum COMPONENT_INFO { COMPONENT_POSITION = 0, COMPONENT_PHYSICS, COMPONENT_RENDERABLE }; </code></pre> <p>Entity.h</p> <pre><code>class Entity { public: std::bitset&lt;NUM_COMPONENTS&gt; componentBits; std::map&lt;COMPONENT_INFO, Component*&gt; components; .. .. Component *getComponent(COMPONENT_INFO inf) { return components[inf]; } }; </code></pre> <p>And my System class updates every entity per frame like that :</p> <pre><code>void update(Entity *e, float delta) { PositionComponent *cmp=(PositionComponent*)e-&gt;getComponent(COMPONENT_INFO::COMPONENT_PHYSICS); //x += 1.0f; cmp-&gt;x += 1.0f; } </code></pre> <p>Everything works as intended, but I have a huge performance problem in accessing the map. When I create 10000 entities and iterate through them (the system iterates through actually), I get 80 FPS with a blue blank system(no visual effects, just plain screen). But when I comment out the access parts and only use <code>x += 1.0f;</code>, FPS increadibly increases to 1000. Like that :</p> <pre><code>void update(Entity *e, float delta) { x += 1.0f; //btw the system has a local x value. } </code></pre> <p>So the problem is simply at accessing the components through the map. What else can I use on a system like that ? Or maybe I am doing something wrong in accessing the map ? </p> <p>Important Edit : This is just a test drive, I mean there might be lots of components per entity, not just 3. I wrote these for just testing purposes. </p>
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    1. USdeniz
    1. USdeniz
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    1. COGiven that you only have three keys, you could use a plain array, or an `std::array<Component*, 3>`. But are you sure the problem really is in the access to map elements?
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      1. USjuanchopanza
    2. COYes the problem is at accessing to map elements (even though i remove cmp->x line, fps is still 80). There won't be 3 keys by the way. For example If i have 64 different components, all of the entities will have to hold them seperately if I use fixed arrays.
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      1. USdeniz
    3. COCan you cache the result of the map in your class to prevent repeated lookup?
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      1. POstd::map Access Speed Is Too Slow?
      1. USNeil Kirk
 

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