nalgebra/nalgebra-sparse/src/ops/serial/cs.rs

229 lines
8.5 KiB
Rust

use crate::cs::CsMatrix;
use crate::ops::serial::{OperationError, OperationErrorKind};
use crate::ops::Op;
use crate::SparseEntryMut;
use nalgebra::{ClosedAdd, ClosedMul, DMatrixSlice, DMatrixSliceMut, Scalar};
use num_traits::{One, Zero};
fn spmm_cs_unexpected_entry() -> OperationError {
OperationError::from_kind_and_message(
OperationErrorKind::InvalidPattern,
String::from("Found unexpected entry that is not present in `c`."),
)
}
/// Helper functionality for implementing CSR/CSC SPMM.
///
/// Since CSR/CSC matrices are basically transpositions of each other, which lets us use the same
/// algorithm for the SPMM implementation. The implementation here is written in a CSR-centric
/// manner. This means that when using it for CSC, the order of the matrices needs to be
/// reversed (since transpose(AB) = transpose(B) * transpose(A) and CSC(A) = transpose(CSR(A)).
///
/// We assume here that the matrices have already been verified to be dimensionally compatible.
pub fn spmm_cs_prealloc_unchecked<T>(
beta: T,
c: &mut CsMatrix<T>,
alpha: T,
a: &CsMatrix<T>,
b: &CsMatrix<T>,
) -> Result<(), OperationError>
where
T: Scalar + ClosedAdd + ClosedMul + Zero + One,
{
let some_val = Zero::zero();
let mut scratchpad_values: Vec<T> = vec![some_val; b.pattern().minor_dim()];
for i in 0..c.pattern().major_dim() {
let a_lane_i = a.get_lane(i).unwrap();
let mut c_lane_i = c.get_lane_mut(i).unwrap();
for (&k, a_ik) in a_lane_i.minor_indices().iter().zip(a_lane_i.values()) {
let b_lane_k = b.get_lane(k).unwrap();
let alpha_aik = alpha.clone() * a_ik.clone();
for (j, b_kj) in b_lane_k.minor_indices().iter().zip(b_lane_k.values()) {
// use a dense scatter vector to accumulate non-zeros quickly
unsafe {
*scratchpad_values.get_unchecked_mut(*j) += alpha_aik.clone() * b_kj.clone();
}
}
}
//Get indices from C pattern and gather from the dense scratchpad_values
let (indices, values) = c_lane_i.indices_and_values_mut();
values
.iter_mut()
.zip(indices)
.for_each(|(output_ref, index)| unsafe {
*output_ref = beta.clone() * output_ref.clone()
+ scratchpad_values.get_unchecked(*index).clone();
*scratchpad_values.get_unchecked_mut(*index) = Zero::zero();
});
}
Ok(())
}
pub fn spmm_cs_prealloc_checked<T>(
beta: T,
c: &mut CsMatrix<T>,
alpha: T,
a: &CsMatrix<T>,
b: &CsMatrix<T>,
) -> Result<(), OperationError>
where
T: Scalar + ClosedAdd + ClosedMul + Zero + One,
{
for i in 0..c.pattern().major_dim() {
let a_lane_i = a.get_lane(i).unwrap();
let mut c_lane_i = c.get_lane_mut(i).unwrap();
for c_ij in c_lane_i.values_mut() {
*c_ij = beta.clone() * c_ij.clone();
}
for (&k, a_ik) in a_lane_i.minor_indices().iter().zip(a_lane_i.values()) {
let b_lane_k = b.get_lane(k).unwrap();
let (mut c_lane_i_cols, mut c_lane_i_values) = c_lane_i.indices_and_values_mut();
let alpha_aik = alpha.clone() * a_ik.clone();
for (j, b_kj) in b_lane_k.minor_indices().iter().zip(b_lane_k.values()) {
// Determine the location in C to append the value
let (c_local_idx, _) = c_lane_i_cols
.iter()
.enumerate()
.find(|(_, c_col)| *c_col == j)
.ok_or_else(spmm_cs_unexpected_entry)?;
c_lane_i_values[c_local_idx] += alpha_aik.clone() * b_kj.clone();
c_lane_i_cols = &c_lane_i_cols[c_local_idx..];
c_lane_i_values = &mut c_lane_i_values[c_local_idx..];
}
}
}
Ok(())
}
fn spadd_cs_unexpected_entry() -> OperationError {
OperationError::from_kind_and_message(
OperationErrorKind::InvalidPattern,
String::from("Found entry in `op(a)` that is not present in `c`."),
)
}
/// Helper functionality for implementing CSR/CSC SPADD.
pub fn spadd_cs_prealloc<T>(
beta: T,
c: &mut CsMatrix<T>,
alpha: T,
a: Op<&CsMatrix<T>>,
) -> Result<(), OperationError>
where
T: Scalar + ClosedAdd + ClosedMul + Zero + One,
{
match a {
Op::NoOp(a) => {
for (mut c_lane_i, a_lane_i) in c.lane_iter_mut().zip(a.lane_iter()) {
if beta != T::one() {
for c_ij in c_lane_i.values_mut() {
*c_ij *= beta.clone();
}
}
let (mut c_minors, mut c_vals) = c_lane_i.indices_and_values_mut();
let (a_minors, a_vals) = (a_lane_i.minor_indices(), a_lane_i.values());
for (a_col, a_val) in a_minors.iter().zip(a_vals) {
// TODO: Use exponential search instead of linear search.
// If C has substantially more entries in the row than A, then a line search
// will needlessly visit many entries in C.
let (c_idx, _) = c_minors
.iter()
.enumerate()
.find(|(_, c_col)| *c_col == a_col)
.ok_or_else(spadd_cs_unexpected_entry)?;
c_vals[c_idx] += alpha.clone() * a_val.clone();
c_minors = &c_minors[c_idx..];
c_vals = &mut c_vals[c_idx..];
}
}
}
Op::Transpose(a) => {
if beta != T::one() {
for c_ij in c.values_mut() {
*c_ij *= beta.clone();
}
}
for (i, a_lane_i) in a.lane_iter().enumerate() {
for (&j, a_val) in a_lane_i.minor_indices().iter().zip(a_lane_i.values()) {
let a_val = a_val.clone();
let alpha = alpha.clone();
match c.get_entry_mut(j, i).unwrap() {
SparseEntryMut::NonZero(c_ji) => *c_ji += alpha * a_val,
SparseEntryMut::Zero => return Err(spadd_cs_unexpected_entry()),
}
}
}
}
}
Ok(())
}
/// Helper functionality for implementing CSR/CSC SPMM.
///
/// The implementation essentially assumes that `a` is a CSR matrix. To use it with CSC matrices,
/// the transposed operation must be specified for the CSC matrix.
pub fn spmm_cs_dense<T>(
beta: T,
mut c: DMatrixSliceMut<'_, T>,
alpha: T,
a: Op<&CsMatrix<T>>,
b: Op<DMatrixSlice<'_, T>>,
) where
T: Scalar + ClosedAdd + ClosedMul + Zero + One,
{
match a {
Op::NoOp(a) => {
for j in 0..c.ncols() {
let mut c_col_j = c.column_mut(j);
for (c_ij, a_row_i) in c_col_j.iter_mut().zip(a.lane_iter()) {
let mut dot_ij = T::zero();
for (&k, a_ik) in a_row_i.minor_indices().iter().zip(a_row_i.values()) {
let b_contrib = match b {
Op::NoOp(ref b) => b.index((k, j)),
Op::Transpose(ref b) => b.index((j, k)),
};
dot_ij += a_ik.clone() * b_contrib.clone();
}
*c_ij = beta.clone() * c_ij.clone() + alpha.clone() * dot_ij;
}
}
}
Op::Transpose(a) => {
// In this case, we have to pre-multiply C by beta
c *= beta;
for k in 0..a.pattern().major_dim() {
let a_row_k = a.get_lane(k).unwrap();
for (&i, a_ki) in a_row_k.minor_indices().iter().zip(a_row_k.values()) {
let gamma_ki = alpha.clone() * a_ki.clone();
let mut c_row_i = c.row_mut(i);
match b {
Op::NoOp(ref b) => {
let b_row_k = b.row(k);
for (c_ij, b_kj) in c_row_i.iter_mut().zip(b_row_k.iter()) {
*c_ij += gamma_ki.clone() * b_kj.clone();
}
}
Op::Transpose(ref b) => {
let b_col_k = b.column(k);
for (c_ij, b_jk) in c_row_i.iter_mut().zip(b_col_k.iter()) {
*c_ij += gamma_ki.clone() * b_jk.clone();
}
}
}
}
}
}
}
}