From a6e62a99cce6d5dd949c74e86cb4437b6adf7ef9 Mon Sep 17 00:00:00 2001
From: William Ball <wball1@swarthmore.edu>
Date: Thu, 23 Jul 2020 14:30:27 -0700
Subject: [PATCH] added investigations of inserting digits anywhere

---
 .../Cargo.toml                                |  10 ++
 .../src/main.rs                               | 119 ++++++++++++++++++
 2 files changed, 129 insertions(+)
 create mode 100644 rust/insert_digit_anywhere_primes_constant/Cargo.toml
 create mode 100644 rust/insert_digit_anywhere_primes_constant/src/main.rs

diff --git a/rust/insert_digit_anywhere_primes_constant/Cargo.toml b/rust/insert_digit_anywhere_primes_constant/Cargo.toml
new file mode 100644
index 0000000..5c88300
--- /dev/null
+++ b/rust/insert_digit_anywhere_primes_constant/Cargo.toml
@@ -0,0 +1,10 @@
+[package]
+name = "insert_digit_anywhere_primes_constant"
+version = "0.1.0"
+authors = ["William Ball <wball1@swarthmore.edu>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+primal = "0.3.0"
diff --git a/rust/insert_digit_anywhere_primes_constant/src/main.rs b/rust/insert_digit_anywhere_primes_constant/src/main.rs
new file mode 100644
index 0000000..5405e5a
--- /dev/null
+++ b/rust/insert_digit_anywhere_primes_constant/src/main.rs
@@ -0,0 +1,119 @@
+use std::thread;
+use std::collections::HashSet;
+
+const NUM_THREADS: usize = 6;
+const THREAD_SKIP: u64 = 1_000;
+const BASE: u64 = 16;
+
+fn remove_duplicates(ls: Vec<u64>) -> Vec<u64> {
+    let mut hs: HashSet<u64> = HashSet::new();
+    for val in &ls {
+        hs.insert(*val);
+    }
+    hs.iter().map(|x| *x).collect()
+}
+
+fn u64_to_v(x: u64) -> Vec<u64> {
+    let mut ll = Vec::new();
+    let mut x = x;
+    while x > 0 {
+        ll.push(x % BASE);
+        x /= BASE;
+    }
+    ll
+}
+
+fn v_to_u64(ll: Vec<u64>) -> u64 {
+    let mut val = 0;
+    let mut ll = ll;
+    loop {
+        match ll.pop() {
+            Some(v) => {
+                val += v;
+                val *= BASE;
+            }
+            None => break,
+        };
+    }
+    val / BASE
+}
+
+fn step(x: u64) -> Vec<u64> {
+    let mut new_xs = Vec::new();
+    let v_x = u64_to_v(x);
+    for i in 0..v_x.len() + 1 {
+        for d in 0..BASE {
+            let mut v_x = u64_to_v(x);
+            v_x.insert(i, d);
+            let temp = v_to_u64(v_x);
+            if !(i == 0 && d == 0) {
+                if primal::is_prime(temp) {
+                    new_xs.push(temp);
+                }
+            }
+        }
+    }
+    new_xs
+}
+
+fn next(ls: Vec<u64>) -> (f64, Vec<u64>) {
+    let old = ls.len();
+    let mut count = 0;
+    let mut new: Vec<u64> = Vec::new();
+    let mut slices: Vec<Vec<u64>> = Vec::new();
+    let mut children = Vec::with_capacity(NUM_THREADS);
+    let size = ls.len() / NUM_THREADS;
+    for i in 0..(NUM_THREADS - 1) {
+        let mut new = Vec::with_capacity(size);
+        for val in ls.iter().skip(size * i).take(size) {
+            new.push(*val);
+        }
+        slices.push(new);
+    }
+    {
+        let mut new = Vec::new();
+        for val in ls.iter().skip(size * (NUM_THREADS - 1)) {
+            new.push(*val);
+        }
+        slices.push(new);
+    }
+    for slice in slices {
+        children.push(thread::spawn(move || -> (u64, Vec<u64>) {
+            let mut new = Vec::new();
+            let mut count = 0;
+            for oldval in slice {
+                // let mut temp = step(oldval);
+                let temp = step(oldval);
+                count += temp.len() as u64;
+                new.push(oldval + THREAD_SKIP);
+                // new.append(&mut temp);
+            }
+            (count, new)
+        }));
+    }
+    for child in children {
+        let (temp1, mut temp2) = child.join().unwrap();
+        new.append(&mut temp2);
+        count += temp1;
+    }
+    (count as f64 / old as f64, remove_duplicates(new))
+}
+
+fn main() {
+    let mut ls: Vec<u64> = (1..(NUM_THREADS as u64) * THREAD_SKIP)
+        .into_iter()
+        .collect();
+    let mut count: f64;
+    let mut i = 0;
+    let mut total: f64 = 0.0;
+    // let mut ls = primal::Primes::all().take_while(|x| *x < BASE as usize).map(|x| x as u64).collect();
+    loop {
+        let res = next(ls);
+        count = res.0;
+        ls = res.1;
+        i += 1;
+        total += count;
+        let res = total as f64 / i as f64;
+        println!("{}\t{}", res, f64::abs(res / (BASE as f64 / f64::ln(BASE as f64))));
+    }
+}