smichr/sympy — comment on commit ba72d152a68c6cd4ff1e060c51577f0988d1b638
File: sympy/core/add.py line 311
By pernici:

I think that it is useless to call igcd here

```
lcm = reduce(ilcm, dnum, 1)
resid = [lcm/di for di in dnum]
den = lcm/reduce(igcd, resid, 0)
```