From: Greg Burri <greg.burri@gmail.com>
Date: Tue, 18 Apr 2023 19:59:17 +0000 (+0200)
Subject: Add a sample with Rayon crate
X-Git-Url: https://git.euphorik.ch/?a=commitdiff_plain;h=cf006f370227090763697a247d6f0647c0532f07;p=rust_concurrent.git

Add a sample with Rayon crate
---

diff --git a/.vscode/settings.json b/.vscode/settings.json
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+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "95ce90fd5bcc06af55a641a86428ee4229e44e07033963a2290a8e241607ccb9"
+dependencies = [
+ "bumpalo",
+ "log",
+ "once_cell",
+ "proc-macro2",
+ "quote",
+ "syn",
+ "wasm-bindgen-shared",
+]
+
+[[package]]
+name = "wasm-bindgen-macro"
+version = "0.2.84"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4c21f77c0bedc37fd5dc21f897894a5ca01e7bb159884559461862ae90c0b4c5"
+dependencies = [
+ "quote",
+ "wasm-bindgen-macro-support",
+]
+
+[[package]]
+name = "wasm-bindgen-macro-support"
+version = "0.2.84"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2aff81306fcac3c7515ad4e177f521b5c9a15f2b08f4e32d823066102f35a5f6"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+ "wasm-bindgen-backend",
+ "wasm-bindgen-shared",
+]
+
+[[package]]
+name = "wasm-bindgen-shared"
+version = "0.2.84"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0046fef7e28c3804e5e38bfa31ea2a0f73905319b677e57ebe37e49358989b5d"
+
+[[package]]
+name = "weezl"
+version = "0.1.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9193164d4de03a926d909d3bc7c30543cecb35400c02114792c2cae20d5e2dbb"
+
+[[package]]
+name = "zune-inflate"
+version = "0.2.53"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "440a08fd59c6442e4b846ea9b10386c38307eae728b216e1ab2c305d1c9daaf8"
+dependencies = [
+ "simd-adler32",
+]
diff --git a/Cargo.toml b/Cargo.toml
index 6d8c0f2..18e5732 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -6,3 +6,6 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+rayon = "1"
+num = "0.4"
+image = "0.24.0"
diff --git a/src/main.rs b/src/main.rs
index 22a0f50..15aa600 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,28 +1,31 @@
 use std::thread;
 
+mod rayon;
+
 fn main() {
-    spawn_and_join();
+    // spawn_and_join();
+    rayon::mandelbrot();
 }
 
 // Page 500.
 fn spawn_and_join() {
+    println!("===== spawn_and_join =====");
     let mut handles = Vec::<thread::JoinHandle<_>>::new();
     for i in 0..10 {
-        let h =
-            thread::spawn(move || {
-                if i == 5 {
-                    panic!("ERROR"); // Simulate an error.
-                }
-                println!("\nHello from thread {}", i);
-                i + 1
-            });
+        let h = thread::spawn(move || {
+            if i == 5 {
+                panic!("ERROR"); // Simulate an error.
+            }
+            println!("\nHello from thread {}", i);
+            i + 1
+        });
         handles.push(h);
     }
 
     for h in handles {
         match h.join() {
             Ok(r) => println!("\nResult: {}", r),
-            Err(err) => println!("\nError: {:?}", err)
+            Err(err) => println!("\nError: {:?}", err),
         }
     }
-}
\ No newline at end of file
+}
diff --git a/src/rayon.rs b/src/rayon.rs
new file mode 100644
index 0000000..7d3e259
--- /dev/null
+++ b/src/rayon.rs
@@ -0,0 +1,90 @@
+use std::fs::File;
+
+use image::{codecs::png::PngEncoder, ColorType, ImageEncoder};
+use num::Complex;
+use rayon::prelude::{IntoParallelIterator, ParallelIterator};
+
+// Page 508.
+pub fn mandelbrot() {
+    println!("===== rayon =====");
+
+    let width = 1920;
+    let height = 1080;
+    let upper_left = Complex { re: -1.2, im: 0.35 };
+    let lower_right = Complex { re: -1.0, im: 0.2 };
+
+    let mut pixels = vec![0; width * height];
+    let bands: Vec<(usize, &mut [u8])> = pixels.chunks_mut(width).enumerate().collect();
+
+    bands.into_par_iter().for_each(|(i, band)| {
+        let top = i;
+        let band_bounds = (width, 1);
+        let band_upper_left = pixel_to_point((width, height), (0, top), upper_left, lower_right);
+        let band_lower_right =
+            pixel_to_point((width, height), (width, top + 1), upper_left, lower_right);
+        render(band, band_bounds, band_upper_left, band_lower_right);
+    });
+
+    write_image("output.png", &pixels, (width, height)).unwrap();
+}
+
+// page 32.
+fn render(
+    pixels: &mut [u8],
+    bounds: (usize, usize),
+    upper_left: Complex<f64>,
+    lower_right: Complex<f64>,
+) {
+    assert!(pixels.len() == bounds.0 * bounds.1);
+
+    for row in 0..bounds.1 {
+        for column in 0..bounds.0 {
+            let point = pixel_to_point(bounds, (column, row), upper_left, lower_right);
+            pixels[row * bounds.0 + column] = match escape_time(point, 255) {
+                None => 0,
+                Some(count) => 255 - count as u8,
+            };
+        }
+    }
+}
+
+fn escape_time(c: Complex<f64>, limit: usize) -> Option<usize> {
+    let mut z = Complex { re: 0.0, im: 0.0 };
+    for i in 0..limit {
+        if z.norm_sqr() > 4.0 {
+            return Some(i);
+        }
+        z = z * z + c;
+    }
+    None
+}
+
+fn pixel_to_point(
+    bounds: (usize, usize),
+    pixel: (usize, usize),
+    upper_left: Complex<f64>,
+    lower_right: Complex<f64>,
+) -> Complex<f64> {
+    let (width, height) = (
+        lower_right.re - upper_left.re,
+        upper_left.im - lower_right.im,
+    );
+    Complex {
+        re: upper_left.re + pixel.0 as f64 * width / bounds.0 as f64,
+        im: upper_left.im - pixel.1 as f64 * height / bounds.1 as f64,
+    }
+}
+
+fn write_image(
+    filename: &str,
+    pixels: &[u8],
+    bounds: (usize, usize),
+) -> Result<(), std::io::Error> {
+    let output = File::create(filename)?;
+    let encoder = PngEncoder::new(output);
+    encoder
+        .write_image(&pixels, bounds.0 as u32, bounds.1 as u32, ColorType::L8)
+        .unwrap(); // TODO: use '?'.
+
+    Ok(())
+}