Array types

This document explains how to use array types on GPU, just as on CPU.

Array types perform array and tensor operations on encrypted data, encapsulating the logic for iteration over array elements and array shape logic.

API elements discussed in this document

• GpuFheUint32Array: an n-d array of Uint32 encrypted values. Variants are available for all supported integer types and booleans.

Array types example

use tfhe::{ConfigBuilder, set_server_key, ClearArray, ClientKey, CompressedServerKey};
use tfhe::array::GpuFheUint32Array;
use tfhe::prelude::*;

fn main() {
    let config = ConfigBuilder::default().build();

    let cks = ClientKey::generate(config);
    let compressed_server_key = CompressedServerKey::new(&cks);

    let gpu_key = compressed_server_key.decompress_to_gpu();
    set_server_key(gpu_key);

    let num_elems = 4 * 4;
    let clear_xs = (0..num_elems as u32).collect::<Vec<_>>();
    let clear_ys = vec![1u32; num_elems];

    // Encrypted 2D array with values
    // [[  0,  1,  2,  3]
    //  [  4,  5,  6,  7]
    //  [  8,  9, 10, 11]
    //  [ 12, 13, 14, 15]]
    let xs = GpuFheUint32Array::try_encrypt((clear_xs.as_slice(), vec![4, 4]), &cks).unwrap();
    // Encrypted 2D array with values
    // [[  1,  1,  1,  1]
    //  [  1,  1,  1,  1]
    //  [  1,  1,  1,  1]
    //  [  1,  1,  1,  1]]
    let ys = GpuFheUint32Array::try_encrypt((clear_ys.as_slice(), vec![4, 4]), &cks).unwrap();

    assert_eq!(xs.num_dim(), 2);
    assert_eq!(xs.shape(), &[4, 4]);
    assert_eq!(ys.num_dim(), 2);
    assert_eq!(ys.shape(), &[4, 4]);

    // Take a sub slice
    //  [[ 10, 11]
    //   [ 14, 15]]
    let xss = xs.slice(&[2..4, 2..4]);
    // Take a sub slice
    //  [[  1,  1]
    //   [  1,  1]]
    let yss = ys.slice(&[2..4, 2..4]);

    assert_eq!(xss.num_dim(), 2);
    assert_eq!(xss.shape(), &[2, 2]);
    assert_eq!(yss.num_dim(), 2);
    assert_eq!(yss.shape(), &[2, 2]);

    let r = &xss + &yss;

    // Result is
    //  [[ 11, 12]
    //   [ 15, 16]]
    let result: Vec<u32> = r.decrypt(&cks);
    assert_eq!(result, vec![11, 12, 15, 16]);

    // Clear 2D array with values
    //  [[  10,  20]
    //   [  30,  40]]
    let clear_array = ClearArray::new(vec![10u32, 20u32, 30u32, 40u32], vec![2, 2]);
    let r = &xss + &clear_array;

    // Result is
    //  [[ 20, 31]
    //   [ 44, 55]]
    let r: Vec<u32> = r.decrypt(&cks);
    assert_eq!(r, vec![20, 31, 44, 55]);
}