https://mpmath.org/doc/current/setup.html#using-gmpy-optional recommends using gmpy but does not say how to install that package. It would be helpful to indicate that up-to-date pip package is called gmpy2 (https://pypi.org/project/gmpy2/), whereas "pip install gmpy" fails with complaints about missing longintrepr.h or other, obscure compiler errors.