* We add a double_and_add method that computes 2 * self + other more
efficiently than just doubling + addition; this is not used anywhere
yet, but I am planning on fiddling with it to see if we can leverage
it somehow. (See zcash/zcash#3924 for details)
* We handle constant scalars better:
* We skip the most-significant constant zeroes to avoid unnecessary
doubling
* When intermediate bits of the scalar are constants, instead of
conditionally adding, we directly use the value of the bit to
decide whether to add or not.
Co-authored-by: Dev Ojha <ValarDragon@users.noreply.github.com>
Co-authored-by: weikeng <w.k@berkeley.edu>