On Thursday, 27 October 2022 at 17:17:01 UTC, ab wrote:
How can I prevent the compiler from removing the code I want to
measure?
With many C compilers, you can use volatile assembly blocks for
that. With LDC -O3, a regular assembly block also does the trick
currently:
```D
void main()
{
import std.datetime.stopwatch;
import std.stdio: write, writeln, writef, writefln;
import std.conv : to;
void f0() {}
void f1()
{
foreach(i; 0..4_000_000)
{
// nothing, loop gets optimized out
}
}
void f2()
{
foreach(i; 0..4_000_000)
{
// defeat optimizations
asm @safe pure nothrow @nogc {}
}
}
auto r = benchmark!(f0, f1, f2)(1);
writeln(r[0]); // 4 μs
writeln(r[1]); // 4 μs
writeln(r[2]); // 1 ms
}
```
