SummationByParts/sbp/src/operators/algos.rs

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2021-01-18 21:37:24 +00:00
use super::*;
#[inline(always)]
pub(crate) fn diff_op_1d(
block: &[&[Float]],
diag: &[Float],
symmetry: Symmetry,
optype: OperatorType,
prev: ArrayView1<Float>,
mut fut: ArrayViewMut1<Float>,
) {
assert_eq!(prev.shape(), fut.shape());
let nx = prev.shape()[0];
assert!(nx >= 2 * block.len());
let dx = if optype == OperatorType::H2 {
1.0 / (nx - 2) as Float
} else {
1.0 / (nx - 1) as Float
};
let idx = 1.0 / dx;
for (bl, f) in block.iter().zip(&mut fut) {
let diff = bl
.iter()
.zip(prev.iter())
.map(|(x, y)| x * y)
.sum::<Float>();
*f = diff * idx;
}
// The window needs to be aligned to the diagonal elements,
// based on the block size
let window_elems_to_skip = block.len() - ((diag.len() - 1) / 2);
for (window, f) in prev
.windows(diag.len())
.into_iter()
.skip(window_elems_to_skip)
.zip(fut.iter_mut().skip(block.len()))
.take(nx - 2 * block.len())
{
let diff = diag.iter().zip(&window).map(|(x, y)| x * y).sum::<Float>();
*f = diff * idx;
}
for (bl, f) in block.iter().zip(fut.iter_mut().rev()) {
let diff = bl
.iter()
.zip(prev.iter().rev())
.map(|(x, y)| x * y)
.sum::<Float>();
*f = idx
* if symmetry == Symmetry::Symmetric {
diff
} else {
-diff
};
}
}
#[derive(PartialEq, Copy, Clone)]
pub(crate) enum Symmetry {
Symmetric,
AntiSymmetric,
}
#[derive(PartialEq, Copy, Clone)]
pub(crate) enum OperatorType {
Normal,
H2,
}
#[inline(always)]
#[allow(unused)]
pub(crate) fn diff_op_col_naive(
block: &'static [&'static [Float]],
diag: &'static [Float],
symmetry: Symmetry,
optype: OperatorType,
) -> impl Fn(ArrayView2<Float>, ArrayViewMut2<Float>) {
#[inline(always)]
move |prev: ArrayView2<Float>, mut fut: ArrayViewMut2<Float>| {
assert_eq!(prev.shape(), fut.shape());
let nx = prev.shape()[1];
assert!(nx >= 2 * block.len());
assert_eq!(prev.strides()[0], 1);
assert_eq!(fut.strides()[0], 1);
let dx = if optype == OperatorType::H2 {
1.0 / (nx - 2) as Float
} else {
1.0 / (nx - 1) as Float
};
let idx = 1.0 / dx;
fut.fill(0.0);
// First block
for (bl, mut fut) in block.iter().zip(fut.axis_iter_mut(ndarray::Axis(1))) {
debug_assert_eq!(fut.len(), prev.shape()[0]);
for (&bl, prev) in bl.iter().zip(prev.axis_iter(ndarray::Axis(1))) {
debug_assert_eq!(prev.len(), fut.len());
fut.scaled_add(idx * bl, &prev);
}
}
let half_diag_width = (diag.len() - 1) / 2;
assert!(half_diag_width <= block.len());
// Diagonal entries
for (ifut, mut fut) in fut
.axis_iter_mut(ndarray::Axis(1))
.enumerate()
.skip(block.len())
.take(nx - 2 * block.len())
{
for (id, &d) in diag.iter().enumerate() {
let offset = ifut - half_diag_width + id;
fut.scaled_add(idx * d, &prev.slice(ndarray::s![.., offset]))
}
}
// End block
for (bl, mut fut) in block.iter().zip(fut.axis_iter_mut(ndarray::Axis(1)).rev()) {
fut.fill(0.0);
for (&bl, prev) in bl.iter().zip(prev.axis_iter(ndarray::Axis(1)).rev()) {
if symmetry == Symmetry::Symmetric {
fut.scaled_add(idx * bl, &prev);
} else {
fut.scaled_add(-idx * bl, &prev);
}
}
}
}
}
#[inline(always)]
pub(crate) fn diff_op_col(
block: &'static [&'static [Float]],
diag: &'static [Float],
symmetry: Symmetry,
optype: OperatorType,
) -> impl Fn(ArrayView2<Float>, ArrayViewMut2<Float>) {
diff_op_col_simd(block, diag, symmetry, optype)
}
#[inline(always)]
pub(crate) fn diff_op_col_simd(
block: &'static [&'static [Float]],
diag: &'static [Float],
symmetry: Symmetry,
optype: OperatorType,
) -> impl Fn(ArrayView2<Float>, ArrayViewMut2<Float>) {
#[inline(always)]
move |prev: ArrayView2<Float>, mut fut: ArrayViewMut2<Float>| {
assert_eq!(prev.shape(), fut.shape());
let nx = prev.shape()[1];
assert!(nx >= 2 * block.len());
assert_eq!(prev.strides()[0], 1);
assert_eq!(fut.strides()[0], 1);
let dx = if optype == OperatorType::H2 {
1.0 / (nx - 2) as Float
} else {
1.0 / (nx - 1) as Float
};
let idx = 1.0 / dx;
#[cfg(not(feature = "f32"))]
type SimdT = packed_simd::f64x8;
#[cfg(feature = "f32")]
type SimdT = packed_simd::f32x16;
let ny = prev.shape()[0];
// How many elements that can be simdified
let simdified = SimdT::lanes() * (ny / SimdT::lanes());
let half_diag_width = (diag.len() - 1) / 2;
assert!(half_diag_width <= block.len());
let fut_base_ptr = fut.as_mut_ptr();
let fut_stride = fut.strides()[1];
let fut_ptr = |j, i| {
debug_assert!(j < ny && i < nx);
unsafe { fut_base_ptr.offset(fut_stride * i as isize + j as isize) }
};
let prev_base_ptr = prev.as_ptr();
let prev_stride = prev.strides()[1];
let prev_ptr = |j, i| {
debug_assert!(j < ny && i < nx);
unsafe { prev_base_ptr.offset(prev_stride * i as isize + j as isize) }
};
// Not algo necessary, but gives performance increase
assert_eq!(fut_stride, prev_stride);
// First block
{
for (ifut, &bl) in block.iter().enumerate() {
for j in (0..simdified).step_by(SimdT::lanes()) {
let index_to_simd = |i| unsafe {
// j never moves past end of slice due to step_by and
// rounding down
SimdT::from_slice_unaligned(std::slice::from_raw_parts(
prev_ptr(j, i),
SimdT::lanes(),
))
};
let mut f = SimdT::splat(0.0);
for (iprev, &bl) in bl.iter().enumerate() {
f = index_to_simd(iprev).mul_adde(SimdT::splat(bl), f);
}
f *= idx;
unsafe {
f.write_to_slice_unaligned(std::slice::from_raw_parts_mut(
fut_ptr(j, ifut),
SimdT::lanes(),
));
}
}
for j in simdified..ny {
unsafe {
let mut f = 0.0;
for (iprev, bl) in bl.iter().enumerate() {
f += bl * *prev_ptr(j, iprev);
}
*fut_ptr(j, ifut) = f * idx;
}
}
}
}
// Diagonal elements
{
for ifut in block.len()..nx - block.len() {
for j in (0..simdified).step_by(SimdT::lanes()) {
let index_to_simd = |i| unsafe {
// j never moves past end of slice due to step_by and
// rounding down
SimdT::from_slice_unaligned(std::slice::from_raw_parts(
prev_ptr(j, i),
SimdT::lanes(),
))
};
let mut f = SimdT::splat(0.0);
for (id, &d) in diag.iter().enumerate() {
let offset = ifut - half_diag_width + id;
f = index_to_simd(offset).mul_adde(SimdT::splat(d), f);
}
f *= idx;
unsafe {
// puts simd along stride 1, j never goes past end of slice
f.write_to_slice_unaligned(std::slice::from_raw_parts_mut(
fut_ptr(j, ifut),
SimdT::lanes(),
));
}
}
for j in simdified..ny {
let mut f = 0.0;
for (id, &d) in diag.iter().enumerate() {
let offset = ifut - half_diag_width + id;
unsafe {
f += d * *prev_ptr(j, offset);
}
}
unsafe {
*fut_ptr(j, ifut) = idx * f;
}
}
}
}
// End block
{
// Get blocks and corresponding offsets
// (rev to iterate in ifut increasing order)
for (bl, ifut) in block.iter().zip((0..nx).rev()) {
for j in (0..simdified).step_by(SimdT::lanes()) {
let index_to_simd = |i| unsafe {
// j never moves past end of slice due to step_by and
// rounding down
SimdT::from_slice_unaligned(std::slice::from_raw_parts(
prev_ptr(j, i),
SimdT::lanes(),
))
};
let mut f = SimdT::splat(0.0);
for (&bl, iprev) in bl.iter().zip((0..nx).rev()) {
f = index_to_simd(iprev).mul_adde(SimdT::splat(bl), f);
}
f = if symmetry == Symmetry::Symmetric {
f * idx
} else {
-f * idx
};
unsafe {
f.write_to_slice_unaligned(std::slice::from_raw_parts_mut(
fut_ptr(j, ifut),
SimdT::lanes(),
));
}
}
for j in simdified..ny {
unsafe {
let mut f = 0.0;
for (&bl, iprev) in bl.iter().zip((0..nx).rev()).rev() {
f += bl * *prev_ptr(j, iprev);
}
*fut_ptr(j, ifut) = if symmetry == Symmetry::Symmetric {
f * idx
} else {
-f * idx
};
}
}
}
}
}
}
#[inline(always)]
fn product_fast<'a>(
u: impl Iterator<Item = &'a Float>,
v: impl Iterator<Item = &'a Float>,
) -> Float {
use std::intrinsics::{fadd_fast, fmul_fast};
u.zip(v).fold(0.0, |acc, (&u, &v)| unsafe {
// We do not care about the order of multiplication nor addition
fadd_fast(acc, fmul_fast(u, v))
})
}
#[inline(always)]
pub(crate) fn diff_op_row(
block: &'static [&'static [Float]],
diag: &'static [Float],
symmetry: Symmetry,
optype: OperatorType,
) -> impl Fn(ArrayView2<Float>, ArrayViewMut2<Float>) {
#[inline(always)]
move |prev: ArrayView2<Float>, mut fut: ArrayViewMut2<Float>| {
assert_eq!(prev.shape(), fut.shape());
let nx = prev.shape()[1];
assert!(nx >= 2 * block.len());
assert_eq!(prev.strides()[1], 1);
assert_eq!(fut.strides()[1], 1);
let dx = if optype == OperatorType::H2 {
1.0 / (nx - 2) as Float
} else {
1.0 / (nx - 1) as Float
};
let idx = 1.0 / dx;
for (prev, mut fut) in prev
.axis_iter(ndarray::Axis(0))
.zip(fut.axis_iter_mut(ndarray::Axis(0)))
{
let prev = prev.as_slice().unwrap();
let fut = fut.as_slice_mut().unwrap();
assert_eq!(prev.len(), fut.len());
assert!(prev.len() >= 2 * block.len());
for (bl, f) in block.iter().zip(fut.iter_mut()) {
let diff = product_fast(bl.iter(), prev[..bl.len()].iter());
*f = diff * idx;
}
// The window needs to be aligned to the diagonal elements,
// based on the block size
let window_elems_to_skip = block.len() - ((diag.len() - 1) / 2);
for (window, f) in prev
.windows(diag.len())
.skip(window_elems_to_skip)
.zip(fut.iter_mut().skip(block.len()))
.take(nx - 2 * block.len())
{
let diff = product_fast(diag.iter(), window.iter());
*f = diff * idx;
}
for (bl, f) in block.iter().zip(fut.iter_mut().rev()) {
let diff = product_fast(bl.iter(), prev.iter().rev());
*f = idx
* if symmetry == Symmetry::Symmetric {
diff
} else {
-diff
};
}
}
}
}
#[cfg(feature = "sparse")]
fn sparse_from_block(
block: &[&[Float]],
diag: &[Float],
symmetry: Symmetry,
optype: OperatorType,
n: usize,
) -> sprs::CsMat<Float> {
assert!(n >= 2 * block.len());
let nnz = {
let block_elems = block.iter().fold(0, |acc, x| {
acc + x
.iter()
.fold(0, |acc, &x| if x != 0.0 { acc + 1 } else { acc })
});
let diag_elems = diag
.iter()
.fold(0, |acc, &x| if x != 0.0 { acc + 1 } else { acc });
2 * block_elems + (n - 2 * block.len()) * diag_elems
};
let mut mat = sprs::TriMat::with_capacity((n, n), nnz);
let dx = if optype == OperatorType::H2 {
1.0 / (n - 2) as Float
} else {
1.0 / (n - 1) as Float
};
let idx = 1.0 / dx;
for (j, bl) in block.iter().enumerate() {
for (i, &b) in bl.iter().enumerate() {
if b == 0.0 {
continue;
}
mat.add_triplet(j, i, b * idx);
}
}
for j in block.len()..n - block.len() {
let half_diag_len = diag.len() / 2;
for (&d, i) in diag.iter().zip(j - half_diag_len..) {
if d == 0.0 {
continue;
}
mat.add_triplet(j, i, d * idx);
}
}
for (bl, j) in block.iter().zip((0..n).rev()).rev() {
for (&b, i) in bl.iter().zip((0..n).rev()).rev() {
if b == 0.0 {
continue;
}
if symmetry == Symmetry::AntiSymmetric {
mat.add_triplet(j, i, -b * idx);
} else {
mat.add_triplet(j, i, b * idx);
}
}
}
mat.to_csr()
}
#[cfg(feature = "sparse")]
fn h_matrix(diag: &[Float], n: usize, is_h2: bool) -> sprs::CsMat<Float> {
let h = if is_h2 {
1.0 / (n - 2) as Float
} else {
1.0 / (n - 1) as Float
};
let nmiddle = n - 2 * diag.len();
let iter = diag
.iter()
.chain(std::iter::repeat(&1.0).take(nmiddle))
.chain(diag.iter().rev())
.map(|&x| h * x);
let mut mat = sprs::TriMat::with_capacity((n, n), n);
for (i, d) in iter.enumerate() {
mat.add_triplet(i, i, d);
}
mat.to_csr()
}