• bearophile (47/47) Oct 12 2010 While optimizing D code I have found the built-in dmd profiler very usef...

bearophile <bearophileHUGS lycos.com> writes:

While optimizing D code I have found the built-in dmd profiler very useful. It
gives experimental data about where the code may need improvements, you need
much less guessing.

In some situations I find that a function that takes lot of the running time is
shaped like this, it contains two different big loops:


void foo(int n) {
    // pre-stuff
    foreach (i; 0 .. n) {
        ...
    }
    // middle-stuff
    foreach (i; 0 .. n) {
        ...
    }
    // post-stuff    
}


In this situation often it's only one of the two loops that uses most of the
running time of the foo() function. I may guess, but I'd like the profiler to
give me more data. So sometimes I split the foo() into something like:


void foo1(int n) {
    foreach (i; 0 .. n) {
        ...
    }
}

void foo2(int n) {
    foreach (i; 0 .. n) {
        ...
    }
}

void foo(int n) {
    // pre-stuff
    foo1(n);
    // middle-stuff
    foo2(n);    
    // post-stuff    
}


This allows me to profile how much time the two parts of foo() take. In this
situation in D code I'd like like a profiling "breakpoint":


void foo(int n) {
    // pre-stuff
    foreach (i; 0 .. n) {
        ...
    }
    profile_point(); // ***
    // middle-stuff
    foreach (i; 0 .. n) {
        ...
    }
    // post-stuff    
}



So the profiling gives me the foo timings split in two (or more) parts. Is this
a possible feature?

Bye,
bearophile