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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::>::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, + lower_right: Complex, +) { + 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, limit: usize) -> Option { + 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, + lower_right: Complex, +) -> Complex { + 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(()) +} -- 2.45.2