Code Optimizations

Hey there /prog/, let's talk about optimization or different things we can do to speed up our applications.

Currently I'm writing a game, and it usually takes up around ~50% of my CPU usage on the bigger maps.  I have a vector that contains all of my blocks, enemies, and other things that should be drawn on the screen.

In my draw thread, it could look like this:
player.draw();
for (int bi = 0; bi < blocks.size(); bi++)
{
    if (InCameraView(blocks[bi]))
    {
        draw(blocks[bi]);
    }
}

In my update thread, it looks like:
player.update();
for (int bi = 0; bi < blocks.size(); bi++)
{
    if (InCameraView(blocks[bi]))
    {
        player.TouchGround(blocks[bi]);
        for (int ei = 0; ei < enemies.size(); ei++)
        {
            enemies.update();
            enemies[ei].TouchGround(blocks[bi]);
        }
    }
}

Obviously only an example, and I typically have lots of more objects that are currently being drawn on the screen.  I also understand that it's usually very bad to have nested for loops, but I'm not exactly sure how else I could handle this.

Also, for rendering I have a lot of "switch" blocks to determine what I should render or update.

switch (CurrentWorld)
{
    case Worlds::MainMenu:
        worldMainMenu.draw();
    break
    case Worlds::Level:
        worldLevel.draw();
    break;
}

Also, for updating thread:
while (true)
{
    while (resetTime >= gameTime)
    {
        resetTime -= gameTime;
    switch (CurrentWorld)
    {
            case Worlds::MainMenu:
                mainMenu.update();
            break;
        case Worlds::Level:
            worldLevel.update();
        break;
    }
    }
}

How do you guys like to optimize your applications to run better and use less processing power?

Why not keep a second list of objects that are in view and add/remove objects from that as the player moves, that way you aren't checking everything each time.

Next optimization would be to create zones for your map and sort objects into those zones, so you don't even have to check objects unless they're in the current zone when the player moves.