kryst 3.2.1

Krylov subspace and preconditioned iterative solvers for dense and sparse linear systems, with shared and distributed memory parallelism.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131

use std::sync::Arc;
use std::sync::atomic::{AtomicU64, Ordering};

use super::op::{LinOp, LinOpF64, StructureId, ValuesId};
use crate::algebra::prelude::KrystScalar;
use crate::error::KError;

/// Matrix-free "shell" operator.
pub struct MatShell<S: KrystScalar> {
    m: usize,
    n: usize,
    mv: Arc<dyn Fn(&[S], &mut [S]) + Send + Sync>,
    mvt: Option<Arc<dyn Fn(&[S], &mut [S]) + Send + Sync>>,
    sid: AtomicU64,
    vid: AtomicU64,
}

impl<S: KrystScalar> MatShell<S> {
    pub fn new(
        m: usize,
        n: usize,
        mv: impl Fn(&[S], &mut [S]) + Send + Sync + 'static,
    ) -> Self {
        Self {
            m,
            n,
            mv: Arc::new(mv),
            mvt: None,
            sid: AtomicU64::new(1),
            vid: AtomicU64::new(1),
        }
    }

    pub fn with_transpose(
        mut self,
        mvt: impl Fn(&[S], &mut [S]) + Send + Sync + 'static,
    ) -> Self {
        self.mvt = Some(Arc::new(mvt));
        self
    }

    pub fn bump_values(&self) {
        self.vid.fetch_add(1, Ordering::Relaxed);
    }

    pub fn bump_structure(&self) {
        self.sid.fetch_add(1, Ordering::Relaxed);
    }
}

impl<S: KrystScalar> LinOp for MatShell<S> {
    type S = S;

    fn dims(&self) -> (usize, usize) {
        (self.m, self.n)
    }

    fn matvec(&self, x: &[S], y: &mut [S]) {
        debug_assert_eq!(x.len(), self.n, "MatShell::matvec x.len mismatch");
        debug_assert_eq!(y.len(), self.m, "MatShell::matvec y.len mismatch");
        (self.mv)(x, y)
    }

    fn try_matvec(&self, x: &[S], y: &mut [S]) -> Result<(), KError> {
        if x.len() != self.n || y.len() != self.m {
            return Err(KError::InvalidInput(format!(
                "MatShell::matvec dimension mismatch: A={}x{}, x.len()={}, y.len()={}",
                self.m,
                self.n,
                x.len(),
                y.len()
            )));
        }
        (self.mv)(x, y);
        Ok(())
    }

    fn supports_transpose(&self) -> bool {
        self.mvt.is_some()
    }

    fn t_matvec(&self, x: &[S], y: &mut [S]) {
        debug_assert_eq!(x.len(), self.m, "MatShell::t_matvec x.len mismatch");
        debug_assert_eq!(y.len(), self.n, "MatShell::t_matvec y.len mismatch");
        if let Some(f) = &self.mvt {
            f(x, y);
        } else {
            panic!("LinOp::t_matvec called but supports_transpose() == false");
        }
    }

    fn structure_id(&self) -> StructureId {
        StructureId(self.sid.load(Ordering::Relaxed))
    }
    fn values_id(&self) -> ValuesId {
        ValuesId(self.vid.load(Ordering::Relaxed))
    }
    fn as_any(&self) -> &dyn std::any::Any {
        self
    }
}

impl LinOpF64 for MatShell<f64> {
    #[inline]
    fn dims(&self) -> (usize, usize) {
        LinOp::dims(self)
    }

    #[inline]
    fn matvec(&self, x: &[f64], y: &mut [f64]) {
        LinOp::matvec(self, x, y)
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn mat_shell_try_matvec_reports_dim_mismatch() {
        let op = MatShell::<f64>::new(2, 3, |x, y| {
            for (yi, xi) in y.iter_mut().zip(x.iter()) {
                *yi = *xi;
            }
        });
        let x = vec![1.0, 2.0, 3.0];
        let mut y = vec![0.0; 1];
        let err = op.try_matvec(&x, &mut y).unwrap_err();
        assert!(matches!(err, KError::InvalidInput(_)));
    }
}