comptime sieve

rust/sieve/.exercism/config.json

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+{
+  "authors": [
+    "IanWhitney"
+  ],
+  "contributors": [
+    "ashleygwilliams",
+    "ClashTheBunny",
+    "coriolinus",
+    "cwhakes",
+    "efx",
+    "ErikSchierboom",
+    "IanWhitney",
+    "lutostag",
+    "mkantor",
+    "nfiles",
+    "petertseng",
+    "rofrol",
+    "stringparser",
+    "xakon",
+    "ZapAnton"
+  ],
+  "files": {
+    "solution": [
+      "src/lib.rs",
+      "Cargo.toml"
+    ],
+    "test": [
+      "tests/sieve.rs"
+    ],
+    "example": [
+      ".meta/example.rs"
+    ]
+  },
+  "blurb": "Use the Sieve of Eratosthenes to find all the primes from 2 up to a given number.",
+  "source": "Sieve of Eratosthenes at Wikipedia",
+  "source_url": "https://en.wikipedia.org/wiki/Sieve_of_Eratosthenes"
+}

rust/sieve/.gitignore

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+/target
+Cargo.lock

rust/sieve/Cargo.toml

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+[package]
+name = "sieve"
+version = "0.1.0"
+edition = "2024"
+
+# Not all libraries from crates.io are available in Exercism's test runner.
+# The full list of available libraries is here:
+# https://github.com/exercism/rust-test-runner/blob/main/local-registry/Cargo.toml
+[dependencies]

rust/sieve/HELP.md

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+# Help
+
+## Running the tests
+
+Execute the tests with:
+
+```bash
+$ cargo test
+```
+
+All but the first test have been ignored. After you get the first test to
+pass, open the tests source file which is located in the `tests` directory
+and remove the `#[ignore]` flag from the next test and get the tests to pass
+again. Each separate test is a function with `#[test]` flag above it.
+Continue, until you pass every test.
+
+If you wish to run _only ignored_ tests without editing the tests source file, use:
+
+```bash
+$ cargo test -- --ignored
+```
+
+If you are using Rust 1.51 or later, you can run _all_ tests with
+
+```bash
+$ cargo test -- --include-ignored
+```
+
+To run a specific test, for example `some_test`, you can use:
+
+```bash
+$ cargo test some_test
+```
+
+If the specific test is ignored, use:
+
+```bash
+$ cargo test some_test -- --ignored
+```
+
+To learn more about Rust tests refer to the online [test documentation][rust-tests].
+
+[rust-tests]: https://doc.rust-lang.org/book/ch11-02-running-tests.html
+
+## Submitting your solution
+
+You can submit your solution using the `exercism submit src/lib.rs Cargo.toml` command.
+This command will upload your solution to the Exercism website and print the solution page's URL.
+
+It's possible to submit an incomplete solution which allows you to:
+
+- See how others have completed the exercise
+- Request help from a mentor
+
+## Need to get help?
+
+If you'd like help solving the exercise, check the following pages:
+
+- The [Rust track's documentation](https://exercism.org/docs/tracks/rust)
+- The [Rust track's programming category on the forum](https://forum.exercism.org/c/programming/rust)
+- [Exercism's programming category on the forum](https://forum.exercism.org/c/programming/5)
+- The [Frequently Asked Questions](https://exercism.org/docs/using/faqs)
+
+Should those resources not suffice, you could submit your (incomplete) solution to request mentoring.
+
+## Rust Installation
+
+Refer to the [exercism help page][help-page] for Rust installation and learning
+resources.
+
+## Submitting the solution
+
+Generally you should submit all files in which you implemented your solution (`src/lib.rs` in most cases). If you are using any external crates, please consider submitting the `Cargo.toml` file. This will make the review process faster and clearer.
+
+## Feedback, Issues, Pull Requests
+
+Head to [the forum](https://forum.exercism.org/c/programming/rust/) and create a post to provide feedback about an exercise or if you want to help implement new exercises.
+Members of the rust track team are happy to help!
+
+The GitHub [track repository][github] is the home for all of the Rust exercises.
+
+If you want to know more about Exercism, take a look at the [contribution guide].
+
+## Submitting Incomplete Solutions
+It's possible to submit an incomplete solution so you can see how others have completed the exercise.
+
+[help-page]: https://exercism.org/tracks/rust/learning
+[github]: https://github.com/exercism/rust
+[contribution guide]: https://exercism.org/docs/community/contributors

rust/sieve/README.md

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+# Sieve
+
+Welcome to Sieve on Exercism's Rust Track.
+If you need help running the tests or submitting your code, check out `HELP.md`.
+
+## Introduction
+
+You bought a big box of random computer parts at a garage sale.
+You've started putting the parts together to build custom computers.
+
+You want to test the performance of different combinations of parts, and decide to create your own benchmarking program to see how your computers compare.
+You choose the famous "Sieve of Eratosthenes" algorithm, an ancient algorithm, but one that should push your computers to the limits.
+
+## Instructions
+
+Your task is to create a program that implements the Sieve of Eratosthenes algorithm to find all prime numbers less than or equal to a given number.
+
+A prime number is a number larger than 1 that is only divisible by 1 and itself.
+For example, 2, 3, 5, 7, 11, and 13 are prime numbers.
+By contrast, 6 is _not_ a prime number as it not only divisible by 1 and itself, but also by 2 and 3.
+
+To use the Sieve of Eratosthenes, first, write out all the numbers from 2 up to and including your given number.
+Then, follow these steps:
+
+1. Find the next unmarked number (skipping over marked numbers).
+   This is a prime number.
+2. Mark all the multiples of that prime number as **not** prime.
+
+Repeat the steps until you've gone through every number.
+At the end, all the unmarked numbers are prime.
+
+~~~~exercism/note
+The Sieve of Eratosthenes marks off multiples of each prime using addition (repeatedly adding the prime) or multiplication (directly computing its multiples), rather than checking each number for divisibility.
+
+The tests don't check that you've implemented the algorithm, only that you've come up with the correct primes.
+~~~~
+
+## Example
+
+Let's say you're finding the primes less than or equal to 10.
+
+- Write out 2, 3, 4, 5, 6, 7, 8, 9, 10, leaving them all unmarked.
+
+  ```text
+  2 3 4 5 6 7 8 9 10
+  ```
+
+- 2 is unmarked and is therefore a prime.
+  Mark 4, 6, 8 and 10 as "not prime".
+
+  ```text
+  2 3 [4] 5 [6] 7 [8] 9 [10]
+  ↑
+  ```
+
+- 3 is unmarked and is therefore a prime.
+  Mark 6 and 9 as not prime _(marking 6 is optional - as it's already been marked)_.
+
+  ```text
+  2 3 [4] 5 [6] 7 [8] [9] [10]
+    ↑
+  ```
+
+- 4 is marked as "not prime", so we skip over it.
+
+  ```text
+  2 3 [4] 5 [6] 7 [8] [9] [10]
+       ↑
+  ```
+
+- 5 is unmarked and is therefore a prime.
+  Mark 10 as not prime _(optional - as it's already been marked)_.
+
+  ```text
+  2 3 [4] 5 [6] 7 [8] [9] [10]
+          ↑
+  ```
+
+- 6 is marked as "not prime", so we skip over it.
+
+  ```text
+  2 3 [4] 5 [6] 7 [8] [9] [10]
+             ↑
+  ```
+
+- 7 is unmarked and is therefore a prime.
+
+  ```text
+  2 3 [4] 5 [6] 7 [8] [9] [10]
+                ↑
+  ```
+
+- 8 is marked as "not prime", so we skip over it.
+
+  ```text
+  2 3 [4] 5 [6] 7 [8] [9] [10]
+                   ↑
+  ```
+
+- 9 is marked as "not prime", so we skip over it.
+
+  ```text
+  2 3 [4] 5 [6] 7 [8] [9] [10]
+                       ↑
+  ```
+
+- 10 is marked as "not prime", so we stop as there are no more numbers to check.
+
+  ```text
+  2 3 [4] 5 [6] 7 [8] [9] [10]
+                           ↑
+  ```
+
+You've examined all the numbers and found that 2, 3, 5, and 7 are still unmarked, meaning they're the primes less than or equal to 10.
+
+## Source
+
+### Created by
+
+- @IanWhitney
+
+### Contributed to by
+
+- @ashleygwilliams
+- @ClashTheBunny
+- @coriolinus
+- @cwhakes
+- @efx
+- @ErikSchierboom
+- @IanWhitney
+- @lutostag
+- @mkantor
+- @nfiles
+- @petertseng
+- @rofrol
+- @stringparser
+- @xakon
+- @ZapAnton
+
+### Based on
+
+Sieve of Eratosthenes at Wikipedia - https://en.wikipedia.org/wiki/Sieve_of_Eratosthenes

rust/sieve/src/lib.rs

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+const PRIME_LEN: usize = 10_010;
+const LIMIT: usize = 106_000;
+
+struct PrimeCache {
+    primes: [u64; PRIME_LEN],
+}
+
+impl PrimeCache {
+    const fn new() -> Self {
+        let mut primes = [0; PRIME_LEN];
+        let mut sieve = [true; LIMIT];
+
+        sieve[0] = false;
+        sieve[1] = false;
+
+        let mut i = 2;
+        while i * i < LIMIT {
+            if sieve[i] {
+                let mut j = i * i;
+                while j < LIMIT {
+                    sieve[j] = false;
+                    j += i;
+                }
+            }
+            i += 1;
+        }
+        let mut num = 0;
+        let mut j = 0;
+        while num < LIMIT && j < PRIME_LEN {
+            if sieve[num] {
+                primes[j] = num as u64;
+                j += 1;
+            }
+            num += 1;
+        }
+        Self { primes }
+    }
+}
+
+static CACHE: PrimeCache = PrimeCache::new();
+
+pub fn primes_up_to(upper_bound: u64) -> Vec<u64> {
+    let mut nth = 0;
+    if upper_bound < 2 {
+        return vec![];
+    }
+    while CACHE.primes[nth] <= upper_bound {
+        nth += 1;
+    }
+    let slice = &CACHE.primes[0..nth];
+    slice.to_vec()
+}

rust/sieve/tests/sieve.rs

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+use sieve::*;
+
+#[test]
+fn no_primes_under_two() {
+    let input = 1;
+    let output = primes_up_to(input);
+    let expected = [];
+    assert_eq!(output, expected);
+}
+
+#[test]
+fn find_first_prime() {
+    let input = 2;
+    let output = primes_up_to(input);
+    let expected = [2];
+    assert_eq!(output, expected);
+}
+
+#[test]
+fn find_primes_up_to_10() {
+    let input = 10;
+    let output = primes_up_to(input);
+    let expected = [2, 3, 5, 7];
+    assert_eq!(output, expected);
+}
+
+#[test]
+fn limit_is_prime() {
+    let input = 13;
+    let output = primes_up_to(input);
+    let expected = [2, 3, 5, 7, 11, 13];
+    assert_eq!(output, expected);
+}
+
+#[test]
+fn find_primes_up_to_1000() {
+    let input = 1000;
+    let output = primes_up_to(input);
+    let expected = [
+        2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89,
+        97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181,
+        191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281,
+        283, 293, 307, 311, 313, 317, 331, 337, 347, 349, 353, 359, 367, 373, 379, 383, 389, 397,
+        401, 409, 419, 421, 431, 433, 439, 443, 449, 457, 461, 463, 467, 479, 487, 491, 499, 503,
+        509, 521, 523, 541, 547, 557, 563, 569, 571, 577, 587, 593, 599, 601, 607, 613, 617, 619,
+        631, 641, 643, 647, 653, 659, 661, 673, 677, 683, 691, 701, 709, 719, 727, 733, 739, 743,
+        751, 757, 761, 769, 773, 787, 797, 809, 811, 821, 823, 827, 829, 839, 853, 857, 859, 863,
+        877, 881, 883, 887, 907, 911, 919, 929, 937, 941, 947, 953, 967, 971, 977, 983, 991, 997,
+    ];
+    assert_eq!(output, expected);
+}