subtraction rounding error

[dkfz-med-phys-rad]

Subtraction and further operations seems to be wrong - that is, yields unwanted rounding - for larger numbers, e.g.
insect 100000-500.7 yields 99499.3
insect 1000000-500.7 yields 999499, however should be 999499.3

Further, I tried:

pi147²107*2/2
pi × 147^2 × 107 × (2 / 2)
= 7263870
However, that ought to be 7263874.2947

[sharkdp]

please see #54