memset

I haven’t used this much, but I’ve been working on modding a program in C which does. At first I didn’t quite get what it was up to, and since I like to know both the why and how, I did some digging. The result? I found a very interesting performance boost for using memset to initialize arrays, as well as a simple one liner.. (which is what the program has been using it for). The ‘ ‘ in the code is really ‘ \ 0 ‘ (no spaces)

example: these are equivalent

const ARRAY_LEN;
my_array[ARRAY_LEN];

unsigned int i;
for(i=0; i < ARRAY_LEN; i++)
{
my_array[i] = '';
}

and

memset(&my_array, '', sizeof(my_array));


And it gets better..

The table below compares two different methods for initializing an array of characters: a for-loop versus memset(). As the size of the data being initialized increases, memset() clearly gets the job done much more quickly:

Input size	Initialized with a for-loop	Initialized with memset()
1000	0.016	0.017
10000	0.055	0.013
100000	0.443	0.029
1000000	4.337	0.291

sources: http://www.cppreference.com/wiki/c/string/memset

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