Efficiency of manually written loops vs operator overloads (C++)
- by Sagekilla
Hi all, in the program I'm working on I have 3-element arrays, which I use as mathematical vectors for all intents and purposes.
Through the course of writing my code, I was tempted to just roll my own Vector class with simple +, -, *, /, etc overloads so I can simplify statements like:
for (int i = 0; i < 3; i++)
r[i] = r1[i] - r2[i];
// becomes:
r = r1 - r2;
Which should be more or less identical in generated code. But when it comes to more complicated things, could this really impact my performance heavily? One example that I have in my code is this:
Manually written version:
for (int j = 0; j < 3; j++)
{
p.vel[j] = p.oldVel[j] + (p.oldAcc[j] + p.acc[j]) * dt2 + (p.oldJerk[j] - p.jerk[j]) * dt12;
p.pos[j] = p.oldPos[j] + (p.oldVel[j] + p.vel[j]) * dt2 + (p.oldAcc[j] - p.acc[j]) * dt12;
}
Using a Vector class with operator overloads:
p.vel = p.oldVel + (p.oldAcc + p.acc) * dt2 + (p.oldJerk - p.jerk) * dt12;
p.pos = p.oldPos + (p.oldVel + p.vel) * dt2 + (p.oldAcc - p.acc) * dt12;
I am compiling my code for maximum possible speed, as it's extremely important that this code runs quickly and calculates accurately. So will me relying on my Vector's for these sorts of things really affect me? For those curious, this is part of some numerical integration code which is not trivial to run in my program.
Any insight would be appreciated, as would any idioms or tricks I'm unaware of.
