Change to PCG random number generator algorithm

See http://www.pcg-random.org/ for benefits of PCG over xorshift
Updates #236 #183

Author: iceiix

Cargo.lock

@@ -32,7 +32,7 @@ flate2 = { version = "1.0.13", features = ["rust_backend"], default-features = f
 zip = { version = "0.5.3", features = ["deflate"], default-features = false }
 image = "0.22.3"
 rand = "0.7.2"
-rand_xorshift = "0.2.0"
+rand_pcg = "0.2.1"
 hex = "0.4.0"
 base64 = "0.11.0"
 log = { version = "0.4.8", features = ["std"] }

Cargo.toml

@@ -10,7 +10,7 @@ use crate::model;
 use crate::types::bit::Set;
 use crate::shared::Direction;
 use rand::{self, SeedableRng, Rng};
-use rand_xorshift;
+use rand_pcg;
 
 const NUM_WORKERS: usize = 8;
 
@@ -122,7 +122,7 @@ fn build_func(id: usize, models: Arc<RwLock<model::Factory>>, work_recv: mpsc::R
             Err(_) => return,
         };
 
-        let mut rng = rand_xorshift::XorShiftRng::from_seed([
+        let mut rng = rand_pcg::Pcg32::from_seed([
             ((position.0 as u32) & 0xff) as u8,
             (((position.0 as u32) >> 8) & 0xff) as u8,
             (((position.0 as u32) >> 16) & 0xff) as u8,

src/chunk_builder.rs

@@ -6,7 +6,7 @@ use crate::render;
 use crate::resources;
 use std::time::{SystemTime, UNIX_EPOCH};
 use rand::{self, seq::SliceRandom};
-use rand_xorshift;
+use rand_pcg;
 
 pub struct Logo {
     _shadow: ui::BatchRef,
@@ -101,7 +101,7 @@ impl Logo {
                     text_strings.push(line.to_owned().replace("\r", ""));
                 }
             }
-            let mut r: rand_xorshift::XorShiftRng = rand::SeedableRng::from_seed([45, 0, 0, 0, 64, 0, 0, 0, 32, 0, 0, 0, 12, 0, 0, 0]);
+            let mut r: rand_pcg::Pcg32 = rand::SeedableRng::from_seed([45, 0, 0, 0, 64, 0, 0, 0, 32, 0, 0, 0, 12, 0, 0, 0]);
             text_strings.shuffle(&mut r);
         }