tree fc0d0fd7c34a014d690a7bee8b4b315ebfbab770
parent 0c9acfc0d17e2e3a738a7e5e4be099352abd743e
author Hans Boehm <hboehm@google.com> 1515546403 -0800
committer Hans Boehm <hboehm@google.com> 1515609572 -0800

Fix a couple of square root related performance problems

Bug: 71686706

Always set appr_valid when we set the approximation. The sqrt_CR
constructor used by the pi computation failed to do that.

Have square root evaluate the argument to full precision before
the recursion. That way we evaluate the argument only once and compute
the lesser approximations via simple shifts.

Fix the comment summarizing the Newton iteration computation.

Rename max_prec_needed, since the name confused me while trying to
understand this code again.

Test: Calculator tests + CR tests
Change-Id: I6d704f24579bae5a5edb4c42487acf1be8fdcee6