initial super simple version

Cargo.lock

@@ -0,0 +1,61 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "crossbeam-deque"
+version = "0.8.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "613f8cc01fe9cf1a3eb3d7f488fd2fa8388403e97039e2f73692932e291a770d"
+dependencies = [
+ "crossbeam-epoch",
+ "crossbeam-utils",
+]
+
+[[package]]
+name = "crossbeam-epoch"
+version = "0.9.18"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5b82ac4a3c2ca9c3460964f020e1402edd5753411d7737aa39c3714ad1b5420e"
+dependencies = [
+ "crossbeam-utils",
+]
+
+[[package]]
+name = "crossbeam-utils"
+version = "0.8.19"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "248e3bacc7dc6baa3b21e405ee045c3047101a49145e7e9eca583ab4c2ca5345"
+
+[[package]]
+name = "either"
+version = "1.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a26ae43d7bcc3b814de94796a5e736d4029efb0ee900c12e2d54c993ad1a1e07"
+
+[[package]]
+name = "onebrc"
+version = "0.1.0"
+dependencies = [
+ "rayon",
+]
+
+[[package]]
+name = "rayon"
+version = "1.8.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9c27db03db7734835b3f53954b534c91069375ce6ccaa2e065441e07d9b6cdb1"
+dependencies = [
+ "either",
+ "rayon-core",
+]
+
+[[package]]
+name = "rayon-core"
+version = "1.12.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5ce3fb6ad83f861aac485e76e1985cd109d9a3713802152be56c3b1f0e0658ed"
+dependencies = [
+ "crossbeam-deque",
+ "crossbeam-utils",
+]

Cargo.toml

@@ -6,3 +6,4 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+rayon = "1.8.0"

src/main.rs

@@ -1,3 +1,59 @@
+use std::collections::HashMap;
+use std::fs::File;
+use std::io::Read;
+
 fn main() {
-    println!("Hello, world!");
+    let mut file = File::open("./measurements.txt").expect("error in opening file");
+
+    let mut map = HashMap::new();
+
+    let mut buf = Vec::new();
+
+    file.read_to_end(&mut buf)
+        .expect("error in reading file to memory");
+
+    for line in buf.split(|&x| x == b'\n') {
+        let l = line.len();
+        if l == 0 {
+            continue;
+        }
+
+        let loc = line.iter().position(|&x| x == b';').unwrap();
+
+        let (city, val) = line.split_at(loc);
+        let val = &val[1..];
+
+        let val = String::from_utf8_lossy(val);
+
+        let val: f32 = val.parse().unwrap();
+
+        let (min, sum, max, counter) =
+            map.entry(city)
+                .or_insert((std::f32::MAX, 0.0, std::f32::MIN, 0));
+
+        *min = val.min(*min);
+        *max = val.max(*max);
+        *counter += 1;
+        *sum += val;
+    }
+
+    let mut list: Vec<(&[u8], (f32, f32, f32, usize))> = map.into_iter().collect();
+    list.sort_unstable_by(|(a, _), (b, _)| a.cmp(b));
+
+    let mut output = String::new();
+
+    let l = list.len();
+
+    for (i, (city, (min, mean, max, counter))) in list.into_iter().enumerate() {
+        output.push_str(&format!(
+            "{}={:.1}/{:.1}/{:.1}{}",
+            String::from_utf8_lossy(city),
+            min,
+            mean / counter as f32,
+            max,
+            if i == l - 1 { "" } else { ", " }
+        ));
+    }
+
+    println!("{{{output}}}");
 }