Approximating comparison function

Library Questions
1

Hi,

I am approximating a comparison function with the function f_n(x) mentioned in the following paper,

The function is found on page 232. In order to get the better approximation I need to do more compositions. I am composing the function 17 times and degree n of a function f_n(x) is 4. I am getting following error while I run the program:
etup & Key Generation

Using ring dimension: 512, mult depth 80
terminate called after throwing an instance of ‘lbcrypto::OpenFHEException’
what(): /home/bhavin/Downloads/openfhe-development/src/core/include/lattice/hal/default/dcrtpoly-impl.h:l.698:DropLastElement(): DropLastElement: Removing last element of DCRTPoly renders it invalid.
Aborted (core dumped)

I would really appreciate any leads to figure out the problem.

Bhavin.

2

It looks to me you are running out of levels. Try increasing the multiplicative even further, or consider using bootstrapping if you are using CKKS.

1 Like
3

Thanks very much @Caesar