the amount of threads now adapt to the host system amount of threads

src/main.rs

@@ -8,6 +8,8 @@ pub mod rtweekend;
 pub mod sphere;
 pub mod vec3;
 
+use std::{f64, thread::available_parallelism};
+
 use image::{Pixel, RgbImage};
 use indicatif::{ProgressBar, ProgressStyle};
 use rayon::prelude::*;
@@ -136,9 +138,14 @@ fn main() {
         dist_to_focus,
     );
 
+    let num_threads: usize = match available_parallelism() {
+        Ok(threads) => threads.into(),
+        Err(_) => 1,
+    };
+
     // Render
     rayon::ThreadPoolBuilder::new()
-        .num_threads(11)
+        .num_threads(num_threads)
         .build_global()
         .unwrap();