commit 8838d1497eecd592b88098f8ed63a2445d7d9b9c
Author: Eric Lynema <elynema@gmail.com>
Date:   Mon Sep 1 19:29:52 2025 -0400

    feat: Implement multi-threaded Pi calculator
    
    This commit introduces a new Rust program that calculates the first n
    digits of Pi using the BBP algorithm. The program is multi-threaded and
    allows the user to specify the number of threads to use. It uses the
    `rug` crate for arbitrary-precision arithmetic to ensure the accuracy of
    the calculated digits.
    
    The program can be run from the command line, taking the number of
    digits and the number of threads as arguments.

diff --git a/.gitignore b/.gitignore
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diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..499c787
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,8 @@
+[package]
+name = "pi"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+clap = { version = "4.5.4", features = ["derive"] }
+rug = "1.24.1"
diff --git a/src/main.rs b/src/main.rs
new file mode 100644
index 0000000..b912e8c
--- /dev/null
+++ b/src/main.rs
@@ -0,0 +1,70 @@
+use clap::Parser;
+use rug::{Float, ops::Pow};
+use std::thread;
+
+#[derive(Parser, Debug)]
+#[command(author, version, about, long_about = None)]
+struct Args {
+    /// Number of digits of Pi to calculate
+    n: u32,
+
+    /// Number of threads to use
+    #[arg(short, long, default_value_t = 4)]
+    threads: usize,
+}
+
+fn bbp_term(k: u32, prec: u32) -> Float {
+    let mut term = Float::with_val(prec, 4);
+    term /= Float::with_val(prec, 8 * k + 1);
+
+    let mut term2 = Float::with_val(prec, 2);
+    term2 /= Float::with_val(prec, 8 * k + 4);
+    term -= term2;
+
+    let mut term3 = Float::with_val(prec, 1);
+    term3 /= Float::with_val(prec, 8 * k + 5);
+    term -= term3;
+
+    let mut term4 = Float::with_val(prec, 1);
+    term4 /= Float::with_val(prec, 8 * k + 6);
+    term -= term4;
+
+    let sixteen = Float::with_val(prec, 16);
+    term /= sixteen.pow(k);
+
+    term
+}
+
+fn main() {
+    let args = Args::parse();
+    let n = args.n;
+    let num_threads = args.threads;
+
+    // Precision for rug::Float. We need a bit more than n decimal digits.
+    // log2(10) is approx 3.32. So, we need n * 3.32 bits.
+    let prec = (n as f64 * 3.33).ceil() as u32;
+
+    let terms_per_thread = (n + num_threads as u32 - 1) / num_threads as u32;
+
+    let mut handles = vec![];
+
+    for i in 0..num_threads {
+        let start = i as u32 * terms_per_thread;
+        let end = ((i + 1) as u32 * terms_per_thread).min(n);
+        let handle = thread::spawn(move || {
+            let mut partial_sum = Float::with_val(prec, 0);
+            for k in start..end {
+                partial_sum += bbp_term(k, prec);
+            }
+            partial_sum
+        });
+        handles.push(handle);
+    }
+
+    let mut pi = Float::with_val(prec, 0);
+    for handle in handles {
+        pi += handle.join().unwrap();
+    }
+
+    println!("Pi: {}", pi.to_string_radix(10, Some(n as usize)));
+}
\ No newline at end of file