Calibrate sensitivity and make deterministic

Signed-off-by: Tom Kaitchuck <Tom.Kaitchuck@gmail.com>

Cargo.toml

@@ -97,6 +97,7 @@ fnv = "1.0.5"
 fxhash = "0.2.1"
 hex = "0.4.2"
 rand = "0.8.5"
+pcg-mwc = "0.2.1"
 serde_json = "1.0.59"
 hashbrown = "0.14.3"
 

tests/map_tests.rs

@@ -228,14 +228,18 @@ fn test_key_ref() {
 #[cfg(feature = "std")]
 #[test]
 fn test_byte_dist() {
-    use rand::{rngs::StdRng, SeedableRng, Rng};
+    use rand::{SeedableRng, Rng, RngCore};
+    use pcg_mwc::Mwc256XXA64;
 
-    let mut r = StdRng::seed_from_u64(0xe786_c22b_119c_1479);
+    let mut r = Mwc256XXA64::seed_from_u64(0xe786_c22b_119c_1479);
+    let mut lowest = 2.541;
+    let mut highest = 2.541;
     for _round in 0..100 {
         let mut table: [bool; 256 * 8] = [false; 256 * 8];
         let hasher = RandomState::with_seeds(r.gen(), r.gen(), r.gen(), r.gen());
         for i in 0..128 {
             let mut keys: [u8; 8] = hasher.hash_one(i as u64).to_ne_bytes();
+            //let mut keys = r.next_u64().to_ne_bytes(); //This is a control to test assert sensitivity.
             for idx in 0..8 {
                 while table[idx * 256 + keys[idx] as usize] {
                     keys[idx] = keys[idx].wrapping_add(1);
@@ -259,10 +263,16 @@ fn test_byte_dist() {
             }
             let mean = total_len as f32 / num_seq as f32;
             println!("Mean sequence length = {}", mean);
-            assert!(mean > 1.70);
-            assert!(mean < 3.375);
+            if mean > highest {
+                highest = mean;
+            }
+            if mean < lowest {
+                lowest = mean;
+            }
         }
     }
+    assert!(lowest > 1.9, "Lowest = {}", lowest);
+    assert!(highest < 3.9, "Highest = {}", highest);
 }