c++ - Floating point division vs floating point multiplication

itemprop="text">

Is there any (non-microoptimization)
performance gain by coding

float
            f1 = 200f / 2

in
comparision to

float f2
            = 200f * 0.5

A
professor of mine told me a few years ago that floating point divisions were slower than
floating point multiplications without elaborating the
why.

Does this statement hold for modern PC
architecture?

Update1

In
respect to a comment, please do also consider this
case:

float
            f1;
float f2 = 2
float f3 = 3;
for( i =0 ; i < 1e8;
            i++)
{
 f1 = (i * f2 + i / f3) * 0.5; //or divide by 2.0f,
            respectively
}

Update
2
Quoting from the
comments:

[I want]
to know what are the algorithmic / architectural requirements that cause > division
to be vastly more complicated in hardware than
multiplication

class="post-text" itemprop="text">

class="normal">Answer

Yes, many
CPUs can perform multiplication in 1 or 2 clock cycles but division always takes longer
(although FP division is sometimes faster than integer
division).

If you look at href="https://stackoverflow.com/questions/2858483/how-can-i-compare-the-performance-of-log-and-fp-division-in-c">this
answer you will see that division can exceed 24
cycles.

Why does division take so
much longer than multiplication? If you remember back to grade school, you may recall
that multiplication can essentially be performed with many simultaneous additions.
Division requires iterative subtraction that cannot be performed simultaneously so it
takes longer. In fact, some FP units speed up division by performing a reciprocal
approximation and multiplying by that. It isn't quite as accurate but is somewhat
faster.