Pre-computation to speed many automorphism on the same ciphertext.
The expensive part of homomorphic automorphism is breaking the ciphertext parts into digits. The usual setting is we first rotate the ciphertext parts, then break them into digits. But when we apply many automorphisms it is faster to break the original ciphertext into digits, then rotate the digits (as opposed to first rotate, then break). An BasicAutomorphPrecon object breaks the original ciphertext and keeps the digits, then when you call automorph is only needs to apply the native automorphism and key switching to the digits, which is fast(er).
