qfall_math/integer_mod_q/mat_zq/
trace.rs

1// Copyright © 2023 Marcel Luca Schmidt
2//
3// This file is part of qFALL-math.
4//
5// qFALL-math is free software: you can redistribute it and/or modify it under
6// the terms of the Mozilla Public License Version 2.0 as published by the
7// Mozilla Foundation. See <https://mozilla.org/en-US/MPL/2.0/>.
8
9//! This module contains the implementation of the `trace` function.
10
11use flint_sys::fmpz_mod_mat::fmpz_mod_mat_trace;
12
13use super::MatZq;
14use crate::{error::MathError, integer_mod_q::Zq, traits::MatrixDimensions};
15
16impl MatZq {
17    /// Returns the trace of a matrix and an error,
18    /// if the matrix is not square.
19    ///
20    /// # Examples
21    /// ```
22    /// use qfall_math::integer_mod_q::MatZq;
23    /// use std::str::FromStr;
24    ///
25    /// let matrix = MatZq::from_str("[[1, 2],[3, 4]] mod 5").unwrap();
26    /// let trace = matrix.trace().unwrap();
27    /// ```
28    ///
29    /// # Errors and Failures
30    /// - Returns a [`MathError`] of type [`NoSquareMatrix`](MathError::NoSquareMatrix)
31    ///   if the matrix is not a square matrix
32    pub fn trace(&self) -> Result<Zq, MathError> {
33        // check if matrix is square
34        if self.get_num_rows() != self.get_num_columns() {
35            return Err(MathError::NoSquareMatrix(self.to_string()));
36        }
37
38        let mut out = Zq::from((0, self.get_mod()));
39        unsafe {
40            fmpz_mod_mat_trace(&mut out.value.value, &self.matrix);
41        }
42        Ok(out)
43    }
44}
45
46#[cfg(test)]
47mod test_trace {
48    use crate::integer_mod_q::{MatZq, Zq};
49    use std::str::FromStr;
50
51    /// Test whether `trace` correctly calculates the trace of a matrix
52    #[test]
53    fn trace_works() {
54        let mat_1 = MatZq::from_str("[[5, 2, 0],[2, 8, 0],[0, 0, 4]] mod 10").unwrap();
55        let mat_2 = MatZq::from_str("[[-1, 0],[0, 1]] mod 2").unwrap();
56
57        let trace_1 = mat_1.trace().unwrap();
58        let trace_2 = mat_2.trace().unwrap();
59
60        assert_eq!(Zq::from((7, 10)), trace_1);
61        assert_eq!(Zq::from((0, 2)), trace_2);
62    }
63
64    /// Test whether `trace` works for large values
65    #[test]
66    fn trace_large_values() {
67        let mat_1 = MatZq::from_str(&format!(
68            "[[{}, 5],[1, {}]] mod {}",
69            i64::MAX,
70            i64::MAX,
71            u64::MAX
72        ))
73        .unwrap();
74        let mat_2 = MatZq::from_str(&format!("[[{}]] mod {}", i64::MIN, u64::MAX)).unwrap();
75        let mat_3 = MatZq::from_str(&format!(
76            "[[{}, 5],[1, {}]] mod {}",
77            i64::MIN,
78            i64::MAX,
79            u64::MAX
80        ))
81        .unwrap();
82
83        let trace_1 = mat_1.trace().unwrap();
84        let trace_2 = mat_2.trace().unwrap();
85        let trace_3 = mat_3.trace().unwrap();
86
87        assert_eq!(Zq::from((2 * i64::MAX as u64, u64::MAX)), trace_1);
88        assert_eq!(Zq::from((i64::MIN, u64::MAX)), trace_2);
89        assert_eq!(Zq::from((-1, u64::MAX)), trace_3);
90    }
91
92    /// Ensure that a matrix that is not square yields an error.
93    #[test]
94    fn trace_error_not_squared() {
95        let mat_1 = MatZq::from_str("[[1, 0, 1],[0, 1, 1]] mod 42").unwrap();
96        let mat_2 = MatZq::from_str("[[1, 0],[0, 1],[1, 0]] mod 17").unwrap();
97
98        assert!(mat_1.trace().is_err());
99        assert!(mat_2.trace().is_err());
100    }
101}
qfall_math/integer_mod_q/mat_zq/trace.rs

qfall_math/integer_mod_q/mat_zq/
trace.rs
