forked from M-Labs/nalgebra
567 lines
19 KiB
Rust
567 lines
19 KiB
Rust
//! An implementation of the CSC sparse matrix format.
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use crate::{SparseFormatError, SparseFormatErrorKind};
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use crate::pattern::{SparsityPattern, SparsityPatternFormatError, SparsityPatternIter};
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use std::sync::Arc;
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use std::slice::{IterMut, Iter};
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use std::ops::Range;
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use num_traits::Zero;
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use std::ptr::slice_from_raw_parts_mut;
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use crate::csr::CsrMatrix;
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use nalgebra::Scalar;
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/// A CSC representation of a sparse matrix.
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///
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/// The Compressed Sparse Column (CSC) format is well-suited as a general-purpose storage format
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/// for many sparse matrix applications.
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///
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/// TODO: Storage explanation and examples
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///
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#[derive(Debug, Clone, PartialEq, Eq)]
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pub struct CscMatrix<T> {
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// Cols are major, rows are minor in the sparsity pattern
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sparsity_pattern: Arc<SparsityPattern>,
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values: Vec<T>,
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}
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impl<T> CscMatrix<T> {
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/// Create a zero CSC matrix with no explicitly stored entries.
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pub fn new(nrows: usize, ncols: usize) -> Self {
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Self {
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sparsity_pattern: Arc::new(SparsityPattern::new(ncols, nrows)),
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values: vec![],
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}
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}
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/// The number of rows in the matrix.
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#[inline]
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pub fn nrows(&self) -> usize {
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self.sparsity_pattern.minor_dim()
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}
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/// The number of columns in the matrix.
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#[inline]
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pub fn ncols(&self) -> usize {
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self.sparsity_pattern.major_dim()
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}
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/// The number of non-zeros in the matrix.
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///
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/// Note that this corresponds to the number of explicitly stored entries, *not* the actual
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/// number of algebraically zero entries in the matrix. Explicitly stored entries can still
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/// be zero. Corresponds to the number of entries in the sparsity pattern.
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#[inline]
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pub fn nnz(&self) -> usize {
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self.sparsity_pattern.nnz()
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}
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/// The column offsets defining part of the CSC format.
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#[inline]
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pub fn col_offsets(&self) -> &[usize] {
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self.sparsity_pattern.major_offsets()
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}
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/// The row indices defining part of the CSC format.
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#[inline]
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pub fn row_indices(&self) -> &[usize] {
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self.sparsity_pattern.minor_indices()
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}
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/// The non-zero values defining part of the CSC format.
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#[inline]
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pub fn values(&self) -> &[T] {
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&self.values
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}
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/// Mutable access to the non-zero values.
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#[inline]
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pub fn values_mut(&mut self) -> &mut [T] {
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&mut self.values
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}
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/// Try to construct a CSC matrix from raw CSC data.
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///
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/// It is assumed that each column contains unique and sorted row indices that are in
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/// bounds with respect to the number of rows in the matrix. If this is not the case,
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/// an error is returned to indicate the failure.
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///
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/// An error is returned if the data given does not conform to the CSC storage format.
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/// See the documentation for [CscMatrix](struct.CscMatrix.html) for more information.
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pub fn try_from_csc_data(
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num_rows: usize,
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num_cols: usize,
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col_offsets: Vec<usize>,
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row_indices: Vec<usize>,
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values: Vec<T>,
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) -> Result<Self, SparseFormatError> {
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let pattern = SparsityPattern::try_from_offsets_and_indices(
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num_cols, num_rows, col_offsets, row_indices)
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.map_err(pattern_format_error_to_csc_error)?;
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Self::try_from_pattern_and_values(Arc::new(pattern), values)
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}
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/// Try to construct a CSC matrix from a sparsity pattern and associated non-zero values.
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///
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/// Returns an error if the number of values does not match the number of minor indices
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/// in the pattern.
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pub fn try_from_pattern_and_values(pattern: Arc<SparsityPattern>, values: Vec<T>)
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-> Result<Self, SparseFormatError> {
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if pattern.nnz() == values.len() {
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Ok(Self {
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sparsity_pattern: pattern,
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values,
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})
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} else {
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Err(SparseFormatError::from_kind_and_msg(
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SparseFormatErrorKind::InvalidStructure,
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"Number of values and row indices must be the same"))
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}
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}
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/// An iterator over non-zero triplets (i, j, v).
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///
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/// The iteration happens in column-major fashion, meaning that j increases monotonically,
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/// and i increases monotonically within each row.
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///
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/// Examples
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/// --------
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/// ```
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/// # use nalgebra_sparse::csc::CscMatrix;
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/// let col_offsets = vec![0, 2, 3, 4];
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/// let row_indices = vec![0, 2, 1, 0];
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/// let values = vec![1, 3, 2, 4];
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/// let mut csc = CscMatrix::try_from_csc_data(4, 3, col_offsets, row_indices, values)
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/// .unwrap();
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///
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/// let triplets: Vec<_> = csc.triplet_iter().map(|(i, j, v)| (i, j, *v)).collect();
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/// assert_eq!(triplets, vec![(0, 0, 1), (2, 0, 3), (1, 1, 2), (0, 2, 4)]);
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/// ```
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pub fn triplet_iter(&self) -> CscTripletIter<T> {
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CscTripletIter {
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pattern_iter: self.sparsity_pattern.entries(),
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values_iter: self.values.iter()
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}
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}
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/// A mutable iterator over non-zero triplets (i, j, v).
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///
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/// Iteration happens in the same order as for [triplet_iter](#method.triplet_iter).
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///
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/// Examples
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/// --------
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/// ```
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/// # use nalgebra_sparse::csc::CscMatrix;
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/// let col_offsets = vec![0, 2, 3, 4];
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/// let row_indices = vec![0, 2, 1, 0];
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/// let values = vec![1, 3, 2, 4];
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/// // Using the same data as in the `triplet_iter` example
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/// let mut csc = CscMatrix::try_from_csc_data(4, 3, col_offsets, row_indices, values)
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/// .unwrap();
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///
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/// // Zero out lower-triangular terms
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/// csc.triplet_iter_mut()
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/// .filter(|(i, j, _)| j < i)
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/// .for_each(|(_, _, v)| *v = 0);
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///
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/// let triplets: Vec<_> = csc.triplet_iter().map(|(i, j, v)| (i, j, *v)).collect();
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/// assert_eq!(triplets, vec![(0, 0, 1), (2, 0, 0), (1, 1, 2), (0, 2, 4)]);
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/// ```
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pub fn triplet_iter_mut(&mut self) -> CscTripletIterMut<T> {
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CscTripletIterMut {
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pattern_iter: self.sparsity_pattern.entries(),
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values_mut_iter: self.values.iter_mut()
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}
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}
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/// Return the column at the given column index.
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///
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/// Panics
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/// ------
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/// Panics if column index is out of bounds.
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#[inline]
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pub fn col(&self, index: usize) -> CscCol<T> {
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self.get_col(index)
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.expect("Row index must be in bounds")
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}
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/// Mutable column access for the given column index.
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///
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/// Panics
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/// ------
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/// Panics if column index is out of bounds.
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#[inline]
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pub fn col_mut(&mut self, index: usize) -> CscColMut<T> {
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self.get_col_mut(index)
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.expect("Row index must be in bounds")
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}
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/// Return the column at the given column index, or `None` if out of bounds.
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#[inline]
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pub fn get_col(&self, index: usize) -> Option<CscCol<T>> {
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let range = self.get_index_range(index)?;
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Some(CscCol {
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row_indices: &self.sparsity_pattern.minor_indices()[range.clone()],
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values: &self.values[range],
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nrows: self.nrows()
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})
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}
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/// Mutable column access for the given column index, or `None` if out of bounds.
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#[inline]
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pub fn get_col_mut(&mut self, index: usize) -> Option<CscColMut<T>> {
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let range = self.get_index_range(index)?;
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Some(CscColMut {
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nrows: self.nrows(),
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row_indices: &self.sparsity_pattern.minor_indices()[range.clone()],
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values: &mut self.values[range]
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})
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}
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/// Internal method for simplifying access to a column's data.
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fn get_index_range(&self, col_index: usize) -> Option<Range<usize>> {
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let col_begin = *self.sparsity_pattern.major_offsets().get(col_index)?;
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let col_end = *self.sparsity_pattern.major_offsets().get(col_index + 1)?;
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Some(col_begin .. col_end)
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}
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/// An iterator over columns in the matrix.
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pub fn col_iter(&self) -> CscColIter<T> {
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CscColIter {
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current_col_idx: 0,
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matrix: self
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}
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}
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/// A mutable iterator over columns in the matrix.
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pub fn col_iter_mut(&mut self) -> CscColIterMut<T> {
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CscColIterMut {
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current_col_idx: 0,
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pattern: &self.sparsity_pattern,
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remaining_values: self.values.as_mut_ptr()
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}
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}
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/// Returns the underlying vector containing the values for the explicitly stored entries.
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pub fn take_values(self) -> Vec<T> {
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self.values
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}
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/// Disassembles the CSC matrix into its underlying offset, index and value arrays.
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///
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/// If the matrix contains the sole reference to the sparsity pattern,
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/// then the data is returned as-is. Otherwise, the sparsity pattern is cloned.
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///
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/// Examples
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/// --------
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///
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/// ```
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/// # use nalgebra_sparse::csc::CscMatrix;
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/// let col_offsets = vec![0, 2, 3, 4];
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/// let row_indices = vec![0, 2, 1, 0];
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/// let values = vec![1, 3, 2, 4];
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/// let mut csc = CscMatrix::try_from_csc_data(
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/// 4,
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/// 3,
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/// col_offsets.clone(),
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/// row_indices.clone(),
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/// values.clone())
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/// .unwrap();
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/// let (col_offsets2, row_indices2, values2) = csc.disassemble();
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/// assert_eq!(col_offsets2, col_offsets);
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/// assert_eq!(row_indices2, row_indices);
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/// assert_eq!(values2, values);
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/// ```
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pub fn disassemble(self) -> (Vec<usize>, Vec<usize>, Vec<T>) {
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// Take an Arc to the pattern, which might be the sole reference to the data after
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// taking the values. This is important, because it might let us avoid cloning the data
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// further below.
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let pattern = self.sparsity_pattern;
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let values = self.values;
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// Try to take the pattern out of the `Arc` if possible,
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// otherwise clone the pattern.
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let owned_pattern = Arc::try_unwrap(pattern)
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.unwrap_or_else(|arc| SparsityPattern::clone(&*arc));
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let (offsets, indices) = owned_pattern.disassemble();
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(offsets, indices, values)
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}
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/// Returns the underlying sparsity pattern.
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///
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/// The sparsity pattern is stored internally inside an `Arc`. This allows users to re-use
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/// the same sparsity pattern for multiple matrices without storing the same pattern multiple
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/// times in memory.
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pub fn pattern(&self) -> &Arc<SparsityPattern> {
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&self.sparsity_pattern
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}
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/// Reinterprets the CSC matrix as its transpose represented by a CSR matrix.
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///
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/// This operation does not touch the CSC data, and is effectively a no-op.
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pub fn transpose_as_csr(self) -> CsrMatrix<T> {
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let pattern = self.sparsity_pattern;
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let values = self.values;
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CsrMatrix::try_from_pattern_and_values(pattern, values).unwrap()
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}
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}
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impl<T: Clone + Zero> CscMatrix<T> {
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/// Return the value in the matrix at the given global row/col indices, or `None` if out of
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/// bounds.
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///
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/// If the indices are in bounds, but no explicitly stored entry is associated with it,
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/// `T::zero()` is returned. Note that this method offers no way of distinguishing
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/// explicitly stored zero entries from zero values that are only implicitly represented.
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///
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/// Each call to this function incurs the cost of a binary search among the explicitly
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/// stored column entries for the given row.
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#[inline]
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pub fn get(&self, row_index: usize, col_index: usize) -> Option<T> {
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self.get_col(row_index)?.get(col_index)
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}
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/// Same as `get`, but panics if indices are out of bounds.
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///
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/// Panics
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/// ------
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/// Panics if either index is out of bounds.
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#[inline]
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pub fn index(&self, row_index: usize, col_index: usize) -> T {
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self.get(row_index, col_index).unwrap()
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}
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}
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impl<T> CscMatrix<T>
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where
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T: Scalar + Zero
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{
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/// Compute the transpose of the matrix.
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pub fn transpose(&self) -> CscMatrix<T> {
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CsrMatrix::from(self).transpose_as_csc()
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}
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}
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/// Convert pattern format errors into more meaningful CSC-specific errors.
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///
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/// This ensures that the terminology is consistent: we are talking about rows and columns,
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/// not lanes, major and minor dimensions.
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fn pattern_format_error_to_csc_error(err: SparsityPatternFormatError) -> SparseFormatError {
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use SparsityPatternFormatError::*;
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use SparsityPatternFormatError::DuplicateEntry as PatternDuplicateEntry;
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use SparseFormatError as E;
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use SparseFormatErrorKind as K;
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match err {
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InvalidOffsetArrayLength => E::from_kind_and_msg(
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K::InvalidStructure,
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"Length of col offset array is not equal to ncols + 1."),
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InvalidOffsetFirstLast => E::from_kind_and_msg(
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K::InvalidStructure,
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"First or last col offset is inconsistent with format specification."),
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NonmonotonicOffsets => E::from_kind_and_msg(
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K::InvalidStructure,
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"Col offsets are not monotonically increasing."),
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NonmonotonicMinorIndices => E::from_kind_and_msg(
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K::InvalidStructure,
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"Row indices are not monotonically increasing (sorted) within each column."),
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MinorIndexOutOfBounds => E::from_kind_and_msg(
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K::IndexOutOfBounds,
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"Row indices are out of bounds."),
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PatternDuplicateEntry => E::from_kind_and_msg(
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K::DuplicateEntry,
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"Matrix data contains duplicate entries."),
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}
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}
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/// Iterator type for iterating over triplets in a CSC matrix.
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#[derive(Debug)]
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pub struct CscTripletIter<'a, T> {
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pattern_iter: SparsityPatternIter<'a>,
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values_iter: Iter<'a, T>
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}
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impl<'a, T> Iterator for CscTripletIter<'a, T> {
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type Item = (usize, usize, &'a T);
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fn next(&mut self) -> Option<Self::Item> {
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let next_entry = self.pattern_iter.next();
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let next_value = self.values_iter.next();
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match (next_entry, next_value) {
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(Some((i, j)), Some(v)) => Some((j, i, v)),
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_ => None
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}
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}
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}
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/// Iterator type for mutably iterating over triplets in a CSC matrix.
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#[derive(Debug)]
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pub struct CscTripletIterMut<'a, T> {
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pattern_iter: SparsityPatternIter<'a>,
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values_mut_iter: IterMut<'a, T>
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}
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impl<'a, T> Iterator for CscTripletIterMut<'a, T> {
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type Item = (usize, usize, &'a mut T);
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#[inline]
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fn next(&mut self) -> Option<Self::Item> {
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let next_entry = self.pattern_iter.next();
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let next_value = self.values_mut_iter.next();
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match (next_entry, next_value) {
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(Some((i, j)), Some(v)) => Some((j, i, v)),
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_ => None
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}
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}
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}
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/// An immutable representation of a column in a CSC matrix.
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#[derive(Debug, Clone, PartialEq, Eq)]
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pub struct CscCol<'a, T> {
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nrows: usize,
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row_indices: &'a [usize],
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values: &'a [T],
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}
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/// A mutable representation of a column in a CSC matrix.
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///
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/// Note that only explicitly stored entries can be mutated. The sparsity pattern belonging
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/// to the column cannot be modified.
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#[derive(Debug, PartialEq, Eq)]
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pub struct CscColMut<'a, T> {
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nrows: usize,
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row_indices: &'a [usize],
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values: &'a mut [T]
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}
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/// Implement the methods common to both CscCol and CscColMut
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macro_rules! impl_csc_col_common_methods {
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($name:ty) => {
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impl<'a, T> $name {
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/// The number of global rows in the column.
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#[inline]
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pub fn nrows(&self) -> usize {
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self.nrows
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}
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/// The number of non-zeros in this column.
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#[inline]
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pub fn nnz(&self) -> usize {
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self.row_indices.len()
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}
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/// The row indices corresponding to explicitly stored entries in this column.
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#[inline]
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pub fn row_indices(&self) -> &[usize] {
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self.row_indices
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}
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/// The values corresponding to explicitly stored entries in this column.
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#[inline]
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pub fn values(&self) -> &[T] {
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self.values
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}
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}
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impl<'a, T: Clone + Zero> $name {
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/// Return the value in the matrix at the given global row index, or `None` if out of
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/// bounds.
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///
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/// If the index is in bounds, but no explicitly stored entry is associated with it,
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/// `T::zero()` is returned. Note that this method offers no way of distinguishing
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/// explicitly stored zero entries from zero values that are only implicitly represented.
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///
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/// Each call to this function incurs the cost of a binary search among the explicitly
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/// stored row entries for the current column.
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pub fn get(&self, global_row_index: usize) -> Option<T> {
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let local_index = self.row_indices().binary_search(&global_row_index);
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if let Ok(local_index) = local_index {
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Some(self.values[local_index].clone())
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} else if global_row_index < self.nrows {
|
|
Some(T::zero())
|
|
} else {
|
|
None
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
impl_csc_col_common_methods!(CscCol<'a, T>);
|
|
impl_csc_col_common_methods!(CscColMut<'a, T>);
|
|
|
|
impl<'a, T> CscColMut<'a, T> {
|
|
/// Mutable access to the values corresponding to explicitly stored entries in this column.
|
|
pub fn values_mut(&mut self) -> &mut [T] {
|
|
self.values
|
|
}
|
|
|
|
/// Provides simultaneous access to row indices and mutable values corresponding to the
|
|
/// explicitly stored entries in this column.
|
|
///
|
|
/// This method primarily facilitates low-level access for methods that process data stored
|
|
/// in CSC format directly.
|
|
pub fn rows_and_values_mut(&mut self) -> (&[usize], &mut [T]) {
|
|
(self.row_indices, self.values)
|
|
}
|
|
}
|
|
|
|
/// Column iterator for [CscMatrix](struct.CscMatrix.html).
|
|
pub struct CscColIter<'a, T> {
|
|
// The index of the row that will be returned on the next
|
|
current_col_idx: usize,
|
|
matrix: &'a CscMatrix<T>
|
|
}
|
|
|
|
impl<'a, T> Iterator for CscColIter<'a, T> {
|
|
type Item = CscCol<'a, T>;
|
|
|
|
fn next(&mut self) -> Option<Self::Item> {
|
|
let col = self.matrix.get_col(self.current_col_idx);
|
|
self.current_col_idx += 1;
|
|
col
|
|
}
|
|
}
|
|
|
|
/// Mutable column iterator for [CscMatrix](struct.CscMatrix.html).
|
|
pub struct CscColIterMut<'a, T> {
|
|
current_col_idx: usize,
|
|
pattern: &'a SparsityPattern,
|
|
remaining_values: *mut T,
|
|
}
|
|
|
|
impl<'a, T> Iterator for CscColIterMut<'a, T>
|
|
where
|
|
T: 'a
|
|
{
|
|
type Item = CscColMut<'a, T>;
|
|
|
|
fn next(&mut self) -> Option<Self::Item> {
|
|
let lane = self.pattern.get_lane(self.current_col_idx);
|
|
let nrows = self.pattern.minor_dim();
|
|
|
|
if let Some(row_indices) = lane {
|
|
let count = row_indices.len();
|
|
|
|
// Note: I can't think of any way to construct this iterator without unsafe.
|
|
let values_in_row;
|
|
unsafe {
|
|
values_in_row = &mut *slice_from_raw_parts_mut(self.remaining_values, count);
|
|
self.remaining_values = self.remaining_values.add(count);
|
|
}
|
|
self.current_col_idx += 1;
|
|
|
|
Some(CscColMut {
|
|
nrows,
|
|
row_indices,
|
|
values: values_in_row
|
|
})
|
|
} else {
|
|
None
|
|
}
|
|
}
|
|
} |