From 9aa823971ef63ddeaeed14aba02b5f50058d7fff Mon Sep 17 00:00:00 2001
From: Michael Zhang <mail@mzhang.io>
Date: Tue, 31 Jan 2023 17:56:36 -0600
Subject: [PATCH] Non-collecting parallel iterators

---
 assignment-1/src/main.rs | 18 ++++++++----------
 1 file changed, 8 insertions(+), 10 deletions(-)

diff --git a/assignment-1/src/main.rs b/assignment-1/src/main.rs
index 4b910cc..a3f3a3e 100644
--- a/assignment-1/src/main.rs
+++ b/assignment-1/src/main.rs
@@ -15,9 +15,7 @@ use anyhow::Result;
 use clap::Parser;
 use itertools::Itertools;
 use ordered_float::NotNan;
-use rayon::prelude::{
-  IndexedParallelIterator, IntoParallelIterator, ParallelIterator,
-};
+use rayon::prelude::{IntoParallelIterator, ParallelIterator};
 
 use crate::image::Image;
 use crate::input_file::parse_input_file;
@@ -26,6 +24,7 @@ use crate::scene_data::Object;
 use crate::vec3::Vec3;
 use crate::view::Rect;
 
+/// Viewing distance
 const ARBITRARY_D: f64 = 2.0;
 
 /// Simple raycaster.
@@ -103,15 +102,13 @@ fn main() -> Result<()> {
     }
   };
 
-  // This is an L because par_bridge is unordered
-  let pixels = (0..scene.image_height)
-    .cartesian_product(0..scene.image_width)
-    .collect_vec();
+  let pixels_iter = (0..scene.image_height)
+    .into_par_iter()
+    .flat_map(|x| (0..scene.image_width).into_par_iter().map(move |y| (y, x)));
 
   // Loop through every single pixel of the output file
-  let pixels = pixels
-    .into_par_iter()
-    .map(|(py, px)| {
+  let pixels = pixels_iter
+    .map(|(px, py)| {
       let pixel_in_space = translate_pixel(px, py);
       let ray = Ray::from_endpoints(scene.eye_pos, pixel_in_space);
 
@@ -140,6 +137,7 @@ fn main() -> Result<()> {
     })
     .collect::<Vec<_>>();
 
+  // Construct and emit image
   let image = Image {
     width: scene.image_width,
     height: scene.image_height,