Hi, I have a doubt about optimization.
Until now I dont care about load more than one time a image. So, for example, if I had two classes that need the same image I load two times instead of load one and share two pointers to the image.
But now I need to increase the speed of my games, so I have a cuestion: What is the relation between memory and fps? I can get more Fps wasting less memory, or it is only usefull when I have a limited memory space like in a mobile phone?

Thanks in advance for the help!

Hi, I have a doubt about optimization.
Until now I dont care about load more than one time a image. So, for example, if I had two classes that need the same image I load two times instead of load one and share two pointers to the image.
But now I need to increase the speed of my games, so I have a cuestion: What is the relation between memory and fps? I can get more Fps wasting less memory, or it is only usefull when I have a limited memory space like in a mobile phone?

Thanks in advance for the help!

In my experience, how much memory you use matters very little as long as you're not paging out to disk. What matters more is how your memory is laid out and the subsequent access patterns to those layouts. If you don't access memory in a cache friendly way, your performance will die.

So, the best can I do is to identify where im lossing speed and try to optimize this parts of code?

Im reading about profilers right now, but it seems to be more complex than I expected.

Do you know any good and simple profiler for start to learn about this?

Also Im using SDL, maybe is the moment for start with OpenGL?

Thanks you!

You should definitely profile. Optimizing without a profiler is just hopeless and foolish for all but the simplest of programs. What profiler to use depends on your system. I haven't used Visual Studio in quite some time, but if you're using that then you may be able to use the Performance Analyzer.

Another thing you could do is to add timers to your code; enclose pieces of code you want to time so you can figure out how long that portion took. Be sure to also take note of the total frame time as well so you can see how much time that portion takes up in relation to the entire frame.

If you want a poor man's sampling profiler:

http://stackoverflow.com/questions/375913/what-can-i-use-to-profile-c-code-in-linux/378024#378024

The profiler will tell you what portion of the code to focus your attention on, but it doesn't really tell you anything about why something is slow. You need to at least have an understanding of algorithms and computer architecture (probably also a little dash of operating systems) to be able to know what that "why" is. Typically, people inspect the algorithm first, since that usually yields the largest gains for relatively minimal effort. A terrible algorithm replaced with a good one can yield huge gains, especially as problem sizes increase. But once you're at a fast algorithm, you may be stuck at a wall that's limited by your particular implementation. This is where computer architecture knowledge often becomes useful. People then proceed to optimize out slow instruction sequences with fast ones and also rearrange data to allow for faster access. Sometimes, people flat out "cheat" because they know something specific about the problem and can precompute things and start some computation further along because of those precomputed results.

The top answer to this question gives a pretty good account of how optimizations usually go: http://stackoverflow.com/questions/926266/performance-optimization-strategies-of-last-resort

One thing to keep at the top of your head is that bad cache behavior in your program can result in an orders of magnitutde slowdown compared to the same bad cache behavior from ten years ago!

This is because the disparity between processor speed and memory speed has increased exponentially since then. So today more than ever it is important to access memory in cache friendly ways.

Of course, you should use a profiler to help you identify these spots. But sometimes you can imagine them, for instance if you access data in a "striped" fashion instead of a "linear" fashion, you will likely result in cache misses.

In my case I think the problem with the speed is that, a bad memory access, because the problem is very random. Often the game run perfect and suddenly it become very sloooow.

I have many cuestions about this:

What do you mean with: "access memory in cache friendly way"? Can you explain with a simple example?

About the profilers, if I write my own little proffiler like a class that mesure the time and the number of calls in each frame will be enougth for simple optimizations like this?