6 ms·

Why would you assume the need to deallocate in the loop? Reuse of an already allocated memory location is C optimisation 101.

• scott_s 15y ago
  You're looking at this from the wrong angle. You're looking at the C code and thinking, "How can I optimize this?" What you need to do in this case is look at it and say, "How can I optimize this and still retain the essence of what I want to test?" Your optimizations remove that essence - if you're calling a function that is a part of an API, it will have to allocate and free its own memory. That the code is in a loop is an artifact of the experiment.
  • xd 15y ago
    I'm looking at it from the angle of someone that has spent over a decade in and out of C. The code in the loop is in NO way an "artifact", it's absolutely critical to the comparison. My example in no way removes the essence, especially if we are using "idioms".
    • scott_s 15y ago
      I said the loop is an artifact, not the code in the loop. Their experimental design is "Do x N times, then divide the overall runtime of the program by N to estimate the cost of x." If timing a program that did x once lead to good results, they would do that - but it doesn't, so they don't. You're trying to optimize around the loop, but by doing that, you're changing the x that is being measured.
      • xd 15y ago
        If by x you mean performing a string operation and copying the result to memory .. I still fail to see how allocating and deallocating memory on each iteration is a fair comparison, it's not something I'd expect a competent C developer to do ergo how is that a relevant comparison? I know the aim is to show off the string operation in and of itself so why not leave it there, why the need to bring garbage collection into the mix? Edit: it's the way the garbage collection has been thrown into the mix I'm having difficulty understanding the need for.
      • cube13 15y ago
        Two things potentially different between the two implementations: 1. The C code is stack allocating a pointer in every loop iteration. 2. Cleaning up the memory without(potentially) triggering Python's GC. Is the Python GC getting triggered in this scenario? If not, then this is what's actually happening, with the cleanup happening automatically when the process exits: char x[10000000]; int i; for (i = 0; i < 10000000; i++) { x[i] = malloc(44 * sizeof(char)); sprintf(x, "%d %d", i, i); } If GC is thrown into the mix, the C code is really: char x[1000]; int i; int j=0; for (i = 0; i < 10000000; i++) { x[j] = malloc(44 * sizeof(char)); sprintf(x, "%d %d", i, i); j++; if(j == 1000) { for(j = 0; j < 1000; ++j) free(x[j]); } }