release mode vs debug

Chapter09/Cargo.toml

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+[package]
+name = "Chapter9"
+version = "1.0.0"
+
+[dependencies]
+cpuprofiler = "0.0.2"
+flame = "0.2"
+rand = "0.4.2"
+
+[[bin]]
+name = "performance_release_mode"
+path = "performance_release_mode.rs"

Chapter09/README.md

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+This chapter makes use of Google's [cpuprofiler](http://goog-perftools.sourceforge.net/doc/cpu_profiler.html),
+which needs to be installed separately. It will not be installed through the normal cargo build process.
+
+[GPerftools](https://github.com/gperftools/gperftools) is also available on Github.

Chapter09/performance_release_mode.rs

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+fn main() {
+   let mut res: Vec<Vec<u64>> = vec![vec![0; 512]; 512];
+   for _ in 0..50 {
+      for i in 1..511 {
+         for j in 1..511 {
+            res[j][i] = 2;
+            res[j][i] += res[j-1][i-1];
+            res[j][i] += res[j][i-1];
+            res[j][i] += res[j+1][i-1];
+            res[j][i] += res[j-1][i];
+            res[j][i] += res[j][i];
+            res[j][i] += res[j+1][i];
+            res[j][i] += res[j-1][i+1];
+            res[j][i] += res[j][i+1];
+            res[j][i] += res[j+1][i+1];
+            res[j][i] /= 9;
+         }
+      }
+   }
+}