Problem
Give $n$ scalars ${k_i}$ and $n$ EC points ${P_i}$, calculate $P$ such that
$$P=\sum_{i=0}^n k_i P_i$$
The Pippenger / Bucket Algorithm
Step 1: partition scalars into windows
Let's first partition each scalar into $m$ windows each has $w$ bits, then
$$k_i = k_{i,0} + k_{i,1} 2^{w} + ... + k_{i,(m-1)} 2^{(m-1)w}$$
You can think each scalar $k_i$ as a bignum and representing it as a multi-precision integer with limb size $w$.