On 09/14/2015 08:18 PM, Andrei Alexandrescu wrote:
On 09/13/2015 01:16 PM, Daniel N wrote:
On Sunday, 13 September 2015 at 14:06:46 UTC, Martin Nowak wrote:
struct Foo
{
size_t id;
int opCmp(Foo rhs)
{
if (id < rhs.id) return -1;
if (id == rhs.id) return 0;
else return 1;
}
bool opBinary(string s:"<")(Foo rhs)
{
return id < rhs.id;
}
}
Sorting a million Foos w/ random ids is 37.5% slower with opCmp.
Could you try this?
int opCmp(Foo rhs)
{
return (id > rhs.id) - (id < rhs.id);
}
Apparently that does well with gcc:
http://stackoverflow.com/questions/10996418/efficient-integer-compare-function
-- Andrei
The first version was actually slightly faster when I tested it with
std::sort. (i.e. if only "<" is used). I guess it is optimized to a
simple integer comparison after inlining. In any case, any performance
differences for such simple equivalent functions are random quirks of
the respective back-ends.
