Why is this code slow?

[Csaba]

I know that benchmarks are always controversial and depend on a 
lot of factors. So far, I read that D performs very well in 
benchmarks, as well, if not better, as C.

I wrote a little program that approximates PI using the Leibniz 
formula. I implemented the same thing in C, D and Python, all of 
them execute 1,000,000 iterations 20 times and display the 
average time elapsed.

Here are the results:

C: 0.04s
Python: 0.33s
D: 0.73s

What the hell? D slower than Python? This cannot be real. I am 
sure I am making a mistake here. I'm sharing all 3 programs here:

C: https://pastebin.com/s7e2HFyL
D: https://pastebin.com/fuURdupc
Python: https://pastebin.com/zcXAkSEf

As you can see the function that does the job is exactly the same 
in C and D.

Here are the compile/run commands used:

C: `gcc leibniz.c -lm -oleibc`
D: `gdc leibniz.d -frelease -oleibd`
Python: `python3 leibniz.py`

PS. my CPU is AMD A8-5500B and my OS is Ubuntu Linux, if that 
matters.