• Advertisement
Sign in to follow this  

Unity custom memory allocator

This topic is 3925 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

Recommended Posts

I'm going to be writing a custom memory allocator, and I wanted to run my idea by the community first. I've never written one before but the fact that I want to benefit from the speed this kind of thing can offer I decided it would be a good idea. Basically I want to write a C++ class Called MemoryPool. On creation MemoryPool will run memory = new char[sizeInByes]; where memory is defined as char *memory; During usage that memory chunk will be divided on the basis of what types it's going to store. For example, I'd like to use it for octree and scene object management. So I would do: On level load:
MemoryPool pool(neededBytes);  //creates the block of memory
pool.CreateBank(sizeof(StaticMapObject), numObjects);  //Sets a pointer to a place in memory where numObjects of StaticMapObjects can live in the char array. A counter returns sucessive pointers as they are requested.
pool.CreateBank(sizeof(OctreeNode), numNodes); //Same as other, but for OctreeNodes and in another place in the pool.


Here are my questions: Is it a good idea to use a char array? Should I use an unsigned char array? is malloc better for this application? should the object "banks" be closely packed together? would it matter if the first bank had a 100 meg empty space between it and the next bank? If the spacing between bank affects speed, how can I reduce the space between the banks? How should I handle deleted objects? make a list of pointers to locations of deleted ojects for reuse? That about sums it up. If anybody knows of any resources that do this already please let me know. Also if there are any optimizations I could make here I would be glad if they were pointed out. Thanks in advance.

Share this post


Link to post
Share on other sites
Advertisement
Quote:
Original post by arbuckle911
Is it a good idea to use a char array? Should I use an unsigned char array?
is malloc better for this application?

It's a good idea to use operator new for the particular datatype. That's the only way to ensure proper alignment.
Quote:
should the object "banks" be closely packed together? would it matter if the first bank had a 100 meg empty space between it and the next bank?

It doesn't really matter, assuming a fairly large number of objects. Small object pooled allocators aren't great at cache coherence no matter what you do.

Quote:
If anybody knows of any resources that do this already please let me know.

Check out boost::pool. There is very little reason for anyone to implement their own fixed-size pool allocator.

Share this post


Link to post
Share on other sites
Quote:

It's a good idea to use operator new for the particular datatype. That's the only way to ensure proper alignment.

Ok but, what if I want to make SURE that all the data is in one chunk? Are you saying it would be best to make an array for each object type? If there is an array for each object type, wouldn't there be fragmentation between each array?

Share this post


Link to post
Share on other sites
Quote:
Original post by arbuckle911
Ok but, what if I want to make SURE that all the data is in one chunk? Are you saying it would be best to make an array for each object type? If there is an array for each object type, wouldn't there be fragmentation between each array?

Hmm? A fixed size pool allocator only works on objects of a single size, which pretty much means objects of a single type.

Share this post


Link to post
Share on other sites
ok, I did some reading I get what you mean now. I'll probly just end up creating a "Factory" class that just dishes whatever class I need out from a fixed size array.

Share this post


Link to post
Share on other sites
Sign in to follow this  

  • Advertisement
  • Advertisement
  • Popular Tags

  • Advertisement
  • Popular Now

  • Similar Content

    • By bryandalo
      Good day,

      I just wanted to share our casual game that is available for android.

      Description: Fight your way from the ravenous plant monster for survival through flips. The rules are simple, drag and release your phone screen. Improve your skills and show it to your friends with the games quirky ranks. Select an array of characters using the orb you acquire throughout the game.

      Download: https://play.google.com/store/apps/details?id=com.HellmodeGames.FlipEscape&hl=en
       
      Trailer: 
       
    • By Manuel Berger
      Hello fellow devs!
      Once again I started working on an 2D adventure game and right now I'm doing the character-movement/animation. I'm not a big math guy and I was happy about my solution, but soon I realized that it's flawed.
      My player has 5 walking-animations, mirrored for the left side: up, upright, right, downright, down. With the atan2 function I get the angle between player and destination. To get an index from 0 to 4, I divide PI by 5 and see how many times it goes into the player-destination angle.

      In Pseudo-Code:
      angle = atan2(destination.x - player.x, destination.y - player.y) //swapped y and x to get mirrored angle around the y axis
      index = (int) (angle / (PI / 5));
      PlayAnimation(index); //0 = up, 1 = up_right, 2 = right, 3 = down_right, 4 = down

      Besides the fact that when angle is equal to PI it produces an index of 5, this works like a charm. Or at least I thought so at first. When I tested it, I realized that the up and down animation is playing more often than the others, which is pretty logical, since they have double the angle.

      What I'm trying to achieve is something like this, but with equal angles, so that up and down has the same range as all other directions.

      I can't get my head around it. Any suggestions? Is the whole approach doomed?

      Thank you in advance for any input!
       
    • By khawk
      Watch the latest from Unity.
       
    • By GytisDev
      Hello,
      without going into any details I am looking for any articles or blogs or advice about city building and RTS games in general. I tried to search for these on my own, but would like to see your input also. I want to make a very simple version of a game like Banished or Kingdoms and Castles,  where I would be able to place like two types of buildings, make farms and cut trees for resources while controlling a single worker. I have some problem understanding how these games works in the back-end: how various data can be stored about the map and objects, how grids works, implementing work system (like a little cube (human) walks to a tree and cuts it) and so on. I am also pretty confident in my programming capabilities for such a game. Sorry if I make any mistakes, English is not my native language.
      Thank you in advance.
    • By Ovicior
      Hey,
      So I'm currently working on a rogue-like top-down game that features melee combat. Getting basic weapon stats like power, weight, and range is not a problem. I am, however, having a problem with coming up with a flexible and dynamic system to allow me to quickly create unique effects for the weapons. I want to essentially create a sort of API that is called when appropriate and gives whatever information is necessary (For example, I could opt to use methods called OnPlayerHit() or IfPlayerBleeding() to implement behavior for each weapon). The issue is, I've never actually made a system as flexible as this.
      My current idea is to make a base abstract weapon class, and then have calls to all the methods when appropriate in there (OnPlayerHit() would be called whenever the player's health is subtracted from, for example). This would involve creating a sub-class for every weapon type and overriding each method to make sure the behavior works appropriately. This does not feel very efficient or clean at all. I was thinking of using interfaces to allow for the implementation of whatever "event" is needed (such as having an interface for OnPlayerAttack(), which would force the creation of a method that is called whenever the player attacks something).
       
      Here's a couple unique weapon ideas I have:
      Explosion sword: Create explosion in attack direction.
      Cold sword: Chance to freeze enemies when they are hit.
      Electric sword: On attack, electricity chains damage to nearby enemies.
       
      I'm basically trying to create a sort of API that'll allow me to easily inherit from a base weapon class and add additional behaviors somehow. One thing to know is that I'm on Unity, and swapping the weapon object's weapon component whenever the weapon changes is not at all a good idea. I need some way to contain all this varying data in one Unity component that can contain a Weapon field to hold all this data. Any ideas?
       
      I'm currently considering having a WeaponController class that can contain a Weapon class, which calls all the methods I use to create unique effects in the weapon (Such as OnPlayerAttack()) when appropriate.
  • Advertisement