title: Calculate Pi in C up to a few million digits
body: <p>I am actually very new to C, but for a project, I'd like to be able to calculate the value of Pi from 1 million to at least 32 million decimal places.
  Basically, like what SuperPi/HyperPi does for benchmarking a CPU.</p>
  
  <p>But obviously, the standard C library is incapable of this.</p>
  
  <p>What library can I use, and what algorithm do I use for this task?</p>
  
  <p>And precision too, anyone can cook up a rand() bloat and call it the "Ultimate value of Pi".</p>
  
  <p>My compiler is GCC, so if possible, I'd like the library to be able to compile on it(I have the BigNum library).</p>