DRAFT: CPU Kernel

.github/workflows/ci.yaml

@@ -31,7 +31,9 @@ jobs:
 
     steps:
       - uses: actions/checkout@v4
-      - run: rustup toolchain install $RUST_VERSION --profile minimal
+      - run: |
+          rustup toolchain add nightly-2025-10-20 --profile minimal
+          rustup toolchain install $RUST_VERSION --profile minimal
       - uses: Swatinem/rust-cache@v2
         with:
           cache-on-failure: true
@@ -46,7 +48,9 @@ jobs:
 
     steps:
       - uses: actions/checkout@v4
-      - run: rustup toolchain install $RUST_VERSION --profile minimal
+      - run: |
+          rustup toolchain add nightly-2025-10-20 --profile minimal
+          rustup toolchain install $RUST_VERSION --profile minimal
       - uses: Swatinem/rust-cache@v2
         with:
           cache-on-failure: true
@@ -68,7 +72,9 @@ jobs:
 
     steps:
       - uses: actions/checkout@v4
-      - run: rustup toolchain install $RUST_VERSION --profile minimal
+      - run: |
+          rustup toolchain add nightly-2025-10-20 --profile minimal
+          rustup toolchain install $RUST_VERSION --profile minimal
       - uses: taiki-e/install-action@v2
         with:
           tool: cargo-shear, cargo-msrv

Cargo.toml

@@ -76,3 +76,9 @@ non_ascii_literal = "allow"
 std_instead_of_alloc = "allow"
 std_instead_of_core = "allow"
 float_arithmetic = "allow"
+
+# We're not worried about cryptographic code, integer
+integer_division_remainder_used = "allow"
+
+# We're not concerned about modulo not computing negative numbers
+modulo_arithmetic = "allow"

crates/total-viewsheds/Cargo.toml

@@ -22,6 +22,7 @@ tracing = { version = "0.1.41" }
 tracing-subscriber = { version = "0.3.19", features = ["env-filter"] }
 wgpu = { version = "27", default-features = false, features = ["spirv", "vulkan"] }
 radsort = "0.1.1"
+itertools = "0.11.0"
 
 [dev-dependencies]
 googletest = "0.14.2"

crates/total-viewsheds/src/compute.rs

@@ -1,5 +1,6 @@
 //! The main entrypoint for running computations.
 
+use crate::cpu;
 use color_eyre::{eyre::Ok, Result};
 
 /// Handles all the computations.
@@ -30,6 +31,11 @@ pub struct Compute<'compute> {
     pub longest_lines: Vec<f32>,
 }
 
+/// `NUM_CORES` is the physical number of cores on a machine. Currently hardcoded to 8
+/// as that is what an i9900k has, and is a common configuration.
+/// TODO find a good syscall for this
+const NUM_CORES: usize = 8;
+
 impl<'compute> Compute<'compute> {
     /// Instantiate.
     pub fn new(
@@ -76,10 +82,6 @@ impl<'compute> Compute<'compute> {
             ..Default::default()
         };
 
-        #[expect(
-            clippy::if_then_some_else_none,
-            reason = "The `?` is hard to use in the closure"
-        )]
         let vulkan = if matches!(backend, crate::config::Backend::Vulkan) {
             let elevations = dem.elevations.clone();
             dem.elevations = Vec::new(); // Free up some RAM.
@@ -189,6 +191,32 @@ impl<'compute> Compute<'compute> {
             Vec::new()
         };
 
+        if matches!(self.backend, crate::config::Backend::CPU) {
+            #[expect(
+                clippy::as_conversions,
+                clippy::cast_possible_truncation,
+                reason = "elevations start out as i16s, and i16 -> f32 -> i16 is lossless"
+            )]
+            let elevations = self
+                .dem
+                .elevations
+                .iter()
+                .map(|&x| x as i16)
+                .collect::<Vec<i16>>();
+
+            #[expect(clippy::as_conversions, reason = "u32 -> usize is valid")]
+            let surfaces = cpu::multithreaded_kernel(
+                &elevations,
+                self.dem.max_los_as_points as usize,
+                360,
+                NUM_CORES,
+            );
+
+            self.add_sector_surfaces_to_running_total(&surfaces);
+            self.render_total_surfaces()?;
+            return Ok(());
+        }
+
         for angle in 0..crate::axes::SECTOR_STEPS {
             self.load_or_compute_cache(angle)?;
             let mut sector_ring_data = vec![0; self.total_reserved_rings];
@@ -537,7 +565,7 @@ pub mod test {
             compute.total_surfaces,
             [
                 2687.689, 2546.9956, 2622.3494,
-                2564.7678, 3231.647, 2239.714, 
+                2564.7678, 3231.647, 2239.714,
                 2604.2551, 2186.5012, 1768.3433
             ]
         );