TEST: Drop num_cpus as benchmark dev-dependency

We don't need another dep just to have faster rayon benchmarks (they are
for comparison anyway.)

Author: bluss

Cargo.toml

@@ -45,7 +45,6 @@ serde = { version = "1.0", optional = true }
 defmac = "0.2"
 quickcheck = { version = "0.7.2", default-features = false }
 rawpointer = "0.1"
-num_cpus = "1.2"
 
 [features]
 # Enable blas usage

benches/par_rayon.rs

@@ -9,7 +9,6 @@ extern crate itertools;
 use ndarray::prelude::*;
 use ndarray::parallel::prelude::*;
 
-extern crate num_cpus;
 extern crate test;
 use test::Bencher;
 
@@ -21,9 +20,10 @@ const ADDN: usize = 512;
 use std::cmp::max;
 
 fn set_threads() {
-    let n = max(1, num_cpus::get() / 2);
-    //println!("Using {} threads", n);
-    let _ = rayon::ThreadPoolBuilder::new().num_threads(n).build_global();
+    // Consider setting a fixed number of threads here, for example to avoid
+    // oversubscribing on hyperthreaded cores.
+    // let n = 4;
+    // let _ = rayon::ThreadPoolBuilder::new().num_threads(n).build_global();
 }
 
 #[bench]