Update development guides.

This better documents the development requirements and also the algorithm assessment logic.

Related to #180.

docs/Development.md

@@ -48,7 +48,11 @@ rustup +nightly component add miri
 cargo +nightly install cargo-valgrind
 cargo +nightly install cargo-tarpaulin
 cargo +nightly install cargo-fuzz
-cargo +nightly install cargo-count
+
+# This is only needed if checking the number of lines of unsafe code,
+# which uses a deprecated binary that requires an old nightly to
+# install.
+cargo +nightly install cargo-count --git https://github.com/kbknapp/cargo-count --rev eebe6f8 --locked
 ```
 
 In addition, the following non-Rust dependencies must be installed:

lexical-benchmark/algorithm/division.rs

@@ -42,7 +42,10 @@ fn fast_div(v: u32) -> (u32, u32) {
     #[allow(clippy::manual_div_ceil)]
     let left_end = ((1 << (max_precision + additional_precision)) + divisor - 1) / divisor;
     let quotient = (v.wrapping_mul(left_end)) >> (max_precision + additional_precision);
-    let remainder = v - divisor * quotient;
+    // NOTE: This should never wrap unless the multiplication wraps, which should never
+    // happen in the cases we use it. Since this is only used for algorithm generation
+    // and testing, this will never fail in real scenarios.
+    let remainder = v.wrapping_sub(divisor * quotient);
 
     (quotient, remainder)
 }