diff --git a/Cargo.toml b/Cargo.toml
index 733ad3445..3f07e7f7d 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -28,7 +28,7 @@ version = "1.0"
 default-features = false
 
 [dev-dependencies]
-docopt = "1"
+structopt = "0.3"
 lazy_static = "1"
 rand = "0.7"
 rand_xorshift = "0.2"
diff --git a/ci/compat-Cargo.lock b/ci/compat-Cargo.lock
index aada85bab..8f9e77491 100644
--- a/ci/compat-Cargo.lock
+++ b/ci/compat-Cargo.lock
@@ -13,7 +13,7 @@ name = "andrew"
 version = "0.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "bitflags 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "bitflags 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "line_drawing 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "rusttype 0.7.9 (registry+https://github.com/rust-lang/crates.io-index)",
  "walkdir 2.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -26,12 +26,20 @@ name = "android_glue"
 version = "0.2.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "ansi_term"
+version = "0.11.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "winapi 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "approx"
 version = "0.3.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "num-traits 0.2.11 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num-traits 0.2.5 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -39,6 +47,16 @@ name = "arrayvec"
 version = "0.5.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "atty"
+version = "0.2.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "hermit-abi 0.1.8 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
+ "winapi 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "autocfg"
 version = "0.1.7"
@@ -51,27 +69,28 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "backtrace"
-version = "0.3.45"
+version = "0.3.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "backtrace-sys 0.1.34 (registry+https://github.com/rust-lang/crates.io-index)",
- "cfg-if 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
+ "backtrace-sys 0.1.24 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cfg-if 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
- "rustc-demangle 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rustc-demangle 0.1.9 (registry+https://github.com/rust-lang/crates.io-index)",
+ "winapi 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "backtrace-sys"
-version = "0.1.34"
+version = "0.1.24"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "cc 1.0.50 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cc 1.0.23 (registry+https://github.com/rust-lang/crates.io-index)",
  "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "bitflags"
-version = "1.2.1"
+version = "1.0.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
@@ -89,19 +108,19 @@ name = "calloop"
 version = "0.4.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "mio 0.6.21 (registry+https://github.com/rust-lang/crates.io-index)",
+ "mio 0.6.19 (registry+https://github.com/rust-lang/crates.io-index)",
  "mio-extras 2.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "nix 0.14.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "cc"
-version = "1.0.50"
+version = "1.0.23"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "cfg-if"
-version = "0.1.10"
+version = "0.1.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
@@ -118,16 +137,30 @@ version = "0.17.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "approx 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "num-traits 0.2.11 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num-traits 0.2.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.6.5 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "clap"
+version = "2.33.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "ansi_term 0.11.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "atty 0.2.14 (registry+https://github.com/rust-lang/crates.io-index)",
+ "bitflags 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "strsim 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "textwrap 0.11.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "unicode-width 0.1.7 (registry+https://github.com/rust-lang/crates.io-index)",
+ "vec_map 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "cloudabi"
 version = "0.0.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "bitflags 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "bitflags 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -135,7 +168,7 @@ name = "cocoa"
 version = "0.19.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "bitflags 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "bitflags 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "block 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "core-foundation 0.6.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "core-graphics 0.17.3 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -163,7 +196,7 @@ name = "core-graphics"
 version = "0.17.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "bitflags 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "bitflags 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "core-foundation 0.6.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "foreign-types 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -174,7 +207,7 @@ name = "core-video-sys"
 version = "0.1.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "cfg-if 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cfg-if 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "core-foundation-sys 0.6.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "core-graphics 0.17.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -197,7 +230,7 @@ version = "0.8.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "autocfg 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "cfg-if 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cfg-if 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "crossbeam-utils 0.7.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "lazy_static 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "maybe-uninit 2.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -210,7 +243,7 @@ name = "crossbeam-queue"
 version = "0.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "cfg-if 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cfg-if 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "crossbeam-utils 0.7.2 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -220,7 +253,7 @@ version = "0.7.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "autocfg 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "cfg-if 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cfg-if 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "lazy_static 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -234,7 +267,7 @@ name = "dlib"
 version = "0.4.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libloading 0.5.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libloading 0.5.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -248,7 +281,7 @@ version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "lazy_static 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "regex 1.3.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "regex 1.3.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.104 (registry+https://github.com/rust-lang/crates.io-index)",
  "strsim 0.9.3 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -260,7 +293,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "either"
-version = "1.5.3"
+version = "1.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
@@ -296,7 +329,7 @@ name = "fuchsia-zircon"
 version = "0.3.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "bitflags 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "bitflags 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "fuchsia-zircon-sys 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -310,7 +343,7 @@ name = "getrandom"
 version = "0.1.14"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "cfg-if 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cfg-if 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
  "wasi 0.9.0+wasi-snapshot-preview1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -321,7 +354,7 @@ version = "0.13.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "khronos_api 3.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
+ "log 0.4.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "xml-rs 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -331,7 +364,7 @@ version = "0.14.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "khronos_api 3.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
+ "log 0.4.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "xml-rs 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -340,7 +373,7 @@ name = "glium"
 version = "0.26.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "backtrace 0.3.45 (registry+https://github.com/rust-lang/crates.io-index)",
+ "backtrace 0.3.9 (registry+https://github.com/rust-lang/crates.io-index)",
  "fnv 1.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "gl_generator 0.14.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "glutin 0.23.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -366,8 +399,8 @@ dependencies = [
  "glutin_glx_sys 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "glutin_wgl_sys 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "lazy_static 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "libloading 0.5.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libloading 0.5.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "log 0.4.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "objc 0.2.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "osmesa-sys 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "parking_lot 0.10.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -405,7 +438,7 @@ version = "0.1.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "gl_generator 0.13.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "x11-dl 2.18.5 (registry+https://github.com/rust-lang/crates.io-index)",
+ "x11-dl 2.18.3 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -416,6 +449,14 @@ dependencies = [
  "gl_generator 0.13.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "heck"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "unicode-segmentation 1.6.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "hermit-abi"
 version = "0.1.8"
@@ -468,10 +509,10 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "libloading"
-version = "0.5.2"
+version = "0.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "cc 1.0.50 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cc 1.0.23 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -480,7 +521,7 @@ name = "line_drawing"
 version = "0.7.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "num-traits 0.2.11 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num-traits 0.2.5 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -493,10 +534,10 @@ dependencies = [
 
 [[package]]
 name = "log"
-version = "0.4.8"
+version = "0.4.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "cfg-if 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cfg-if 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -536,16 +577,15 @@ dependencies = [
 
 [[package]]
 name = "mio"
-version = "0.6.21"
+version = "0.6.19"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "cfg-if 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
  "fuchsia-zircon 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "fuchsia-zircon-sys 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "iovec 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "kernel32-sys 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
- "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
+ "log 0.4.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "miow 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "net2 0.2.33 (registry+https://github.com/rust-lang/crates.io-index)",
  "slab 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -558,8 +598,8 @@ version = "2.0.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "lazycell 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "mio 0.6.21 (registry+https://github.com/rust-lang/crates.io-index)",
+ "log 0.4.5 (registry+https://github.com/rust-lang/crates.io-index)",
+ "mio 0.6.19 (registry+https://github.com/rust-lang/crates.io-index)",
  "slab 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -579,7 +619,7 @@ name = "net2"
 version = "0.2.33"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "cfg-if 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cfg-if 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -589,89 +629,80 @@ name = "nix"
 version = "0.14.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "bitflags 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "cc 1.0.50 (registry+https://github.com/rust-lang/crates.io-index)",
- "cfg-if 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
+ "bitflags 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cc 1.0.23 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cfg-if 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
  "void 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "num"
-version = "0.2.1"
+version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "num-bigint 0.2.6 (registry+https://github.com/rust-lang/crates.io-index)",
- "num-complex 0.2.4 (registry+https://github.com/rust-lang/crates.io-index)",
- "num-integer 0.1.42 (registry+https://github.com/rust-lang/crates.io-index)",
- "num-iter 0.1.40 (registry+https://github.com/rust-lang/crates.io-index)",
- "num-rational 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
- "num-traits 0.2.11 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num-bigint 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num-complex 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num-integer 0.1.39 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num-iter 0.1.37 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num-rational 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num-traits 0.2.5 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "num-bigint"
-version = "0.2.6"
+version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "autocfg 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "num-integer 0.1.42 (registry+https://github.com/rust-lang/crates.io-index)",
- "num-traits 0.2.11 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num-integer 0.1.39 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num-traits 0.2.5 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "num-complex"
-version = "0.2.4"
+version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "autocfg 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "num-traits 0.2.11 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num-traits 0.2.5 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "num-integer"
-version = "0.1.42"
+version = "0.1.39"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "autocfg 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "num-traits 0.2.11 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num-traits 0.2.5 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "num-iter"
-version = "0.1.40"
+version = "0.1.37"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "autocfg 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "num-integer 0.1.42 (registry+https://github.com/rust-lang/crates.io-index)",
- "num-traits 0.2.11 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num-integer 0.1.39 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num-traits 0.2.5 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "num-rational"
-version = "0.2.3"
+version = "0.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "autocfg 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "num-bigint 0.2.6 (registry+https://github.com/rust-lang/crates.io-index)",
- "num-integer 0.1.42 (registry+https://github.com/rust-lang/crates.io-index)",
- "num-traits 0.2.11 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num-bigint 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num-integer 0.1.39 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num-traits 0.2.5 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "num-traits"
-version = "0.2.11"
+version = "0.2.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-dependencies = [
- "autocfg 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
-]
 
 [[package]]
 name = "num_cpus"
-version = "1.12.0"
+version = "1.8.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "hermit-abi 0.1.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -698,7 +729,7 @@ name = "ordered-float"
 version = "1.0.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "num-traits 0.2.11 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num-traits 0.2.5 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -723,10 +754,10 @@ name = "parking_lot_core"
 version = "0.7.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "cfg-if 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cfg-if 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "cloudabi 0.0.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
- "redox_syscall 0.1.56 (registry+https://github.com/rust-lang/crates.io-index)",
+ "redox_syscall 0.1.40 (registry+https://github.com/rust-lang/crates.io-index)",
  "smallvec 1.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -738,7 +769,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "pkg-config"
-version = "0.3.17"
+version = "0.3.14"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
@@ -746,6 +777,30 @@ name = "ppv-lite86"
 version = "0.2.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "proc-macro-error"
+version = "0.4.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "proc-macro-error-attr 0.4.11 (registry+https://github.com/rust-lang/crates.io-index)",
+ "proc-macro2 1.0.9 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 1.0.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "version_check 0.9.1 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "proc-macro-error-attr"
+version = "0.4.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "proc-macro2 1.0.9 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 1.0.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn-mid 0.5.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "version_check 0.9.1 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "proc-macro2"
 version = "0.4.30"
@@ -947,13 +1002,13 @@ dependencies = [
  "autocfg 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "crossbeam-deque 0.7.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "doc-comment 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "docopt 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "either 1.5.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "either 1.5.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "lazy_static 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.7.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand_xorshift 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "rayon-core 1.7.0",
  "serde 1.0.104 (registry+https://github.com/rust-lang/crates.io-index)",
+ "structopt 0.3.11 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -965,7 +1020,7 @@ dependencies = [
  "crossbeam-utils 0.7.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "lazy_static 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
- "num_cpus 1.12.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num_cpus 1.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.7.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand_xorshift 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "scoped-tls 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -981,12 +1036,12 @@ dependencies = [
  "glium 0.26.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "lazy_static 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
- "num 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "odds 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.7.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand_xorshift 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "rayon 1.3.0",
- "regex 1.3.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "regex 1.3.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.104 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -1001,28 +1056,28 @@ dependencies = [
 
 [[package]]
 name = "redox_syscall"
-version = "0.1.56"
+version = "0.1.40"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "regex"
-version = "1.3.4"
+version = "1.3.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "aho-corasick 0.7.10 (registry+https://github.com/rust-lang/crates.io-index)",
  "memchr 2.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
- "regex-syntax 0.6.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "regex-syntax 0.6.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "thread_local 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "regex-syntax"
-version = "0.6.16"
+version = "0.6.17"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "rustc-demangle"
-version = "0.1.16"
+version = "0.1.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
@@ -1126,7 +1181,7 @@ version = "0.6.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "andrew 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "bitflags 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "bitflags 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "dlib 0.4.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "lazy_static 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "memmap 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1143,11 +1198,38 @@ dependencies = [
  "byteorder 1.3.4 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "strsim"
+version = "0.8.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "strsim"
 version = "0.9.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "structopt"
+version = "0.3.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "clap 2.33.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "lazy_static 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "structopt-derive 0.4.4 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "structopt-derive"
+version = "0.4.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "heck 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "proc-macro-error 0.4.11 (registry+https://github.com/rust-lang/crates.io-index)",
+ "proc-macro2 1.0.9 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 1.0.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.16 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "syn"
 version = "1.0.16"
@@ -1158,11 +1240,29 @@ dependencies = [
  "unicode-xid 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "syn-mid"
+version = "0.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "proc-macro2 1.0.9 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 1.0.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.16 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "takeable-option"
 version = "0.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "textwrap"
+version = "0.11.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "unicode-width 0.1.7 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "thread_local"
 version = "1.0.1"
@@ -1176,6 +1276,16 @@ name = "unchecked-index"
 version = "0.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "unicode-segmentation"
+version = "1.6.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[[package]]
+name = "unicode-width"
+version = "0.1.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "unicode-xid"
 version = "0.1.0"
@@ -1186,6 +1296,16 @@ name = "unicode-xid"
 version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "vec_map"
+version = "0.8.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[[package]]
+name = "version_check"
+version = "0.9.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "void"
 version = "1.0.2"
@@ -1211,11 +1331,11 @@ name = "wayland-client"
 version = "0.23.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "bitflags 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "bitflags 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "calloop 0.4.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "downcast-rs 1.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
- "mio 0.6.21 (registry+https://github.com/rust-lang/crates.io-index)",
+ "mio 0.6.19 (registry+https://github.com/rust-lang/crates.io-index)",
  "nix 0.14.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "wayland-commons 0.23.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "wayland-scanner 0.23.6 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1236,7 +1356,7 @@ name = "wayland-protocols"
 version = "0.23.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "bitflags 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "bitflags 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "wayland-client 0.23.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "wayland-commons 0.23.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "wayland-scanner 0.23.6 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1304,7 +1424,7 @@ version = "0.21.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "android_glue 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
- "bitflags 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "bitflags 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "cocoa 0.19.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "core-foundation 0.6.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "core-graphics 0.17.3 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1313,8 +1433,8 @@ dependencies = [
  "instant 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "lazy_static 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
- "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "mio 0.6.21 (registry+https://github.com/rust-lang/crates.io-index)",
+ "log 0.4.5 (registry+https://github.com/rust-lang/crates.io-index)",
+ "mio 0.6.19 (registry+https://github.com/rust-lang/crates.io-index)",
  "mio-extras 2.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "objc 0.2.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "parking_lot 0.10.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1323,7 +1443,7 @@ dependencies = [
  "smithay-client-toolkit 0.6.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "wayland-client 0.23.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "x11-dl 2.18.5 (registry+https://github.com/rust-lang/crates.io-index)",
+ "x11-dl 2.18.3 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1337,13 +1457,12 @@ dependencies = [
 
 [[package]]
 name = "x11-dl"
-version = "2.18.5"
+version = "2.18.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
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  "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
- "maybe-uninit 2.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "pkg-config 0.3.17 (registry+https://github.com/rust-lang/crates.io-index)",
+ "pkg-config 0.3.14 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1360,20 +1479,23 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum aho-corasick 0.7.10 (registry+https://github.com/rust-lang/crates.io-index)" = "8716408b8bc624ed7f65d223ddb9ac2d044c0547b6fa4b0d554f3a9540496ada"
 "checksum andrew 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)" = "9b7f09f89872c2b6b29e319377b1fbe91c6f5947df19a25596e121cf19a7b35e"
 "checksum android_glue 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)" = "000444226fcff248f2bc4c7625be32c63caccfecc2723a2b9f78a7487a49c407"
+"checksum ansi_term 0.11.0 (registry+https://github.com/rust-lang/crates.io-index)" = "ee49baf6cb617b853aa8d93bf420db2383fab46d314482ca2803b40d5fde979b"
 "checksum approx 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)" = "f0e60b75072ecd4168020818c0107f2857bb6c4e64252d8d3983f6263b40a5c3"
 "checksum arrayvec 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)" = "cff77d8686867eceff3105329d4698d96c2391c176d5d03adc90c7389162b5b8"
+"checksum atty 0.2.14 (registry+https://github.com/rust-lang/crates.io-index)" = "d9b39be18770d11421cdb1b9947a45dd3f37e93092cbf377614828a319d5fee8"
 "checksum autocfg 0.1.7 (registry+https://github.com/rust-lang/crates.io-index)" = "1d49d90015b3c36167a20fe2810c5cd875ad504b39cff3d4eae7977e6b7c1cb2"
 "checksum autocfg 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "f8aac770f1885fd7e387acedd76065302551364496e46b3dd00860b2f8359b9d"
-"checksum backtrace 0.3.45 (registry+https://github.com/rust-lang/crates.io-index)" = "ad235dabf00f36301792cfe82499880ba54c6486be094d1047b02bacb67c14e8"
-"checksum backtrace-sys 0.1.34 (registry+https://github.com/rust-lang/crates.io-index)" = "ca797db0057bae1a7aa2eef3283a874695455cecf08a43bfb8507ee0ebc1ed69"
-"checksum bitflags 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)" = "cf1de2fe8c75bc145a2f577add951f8134889b4795d47466a54a5c846d691693"
+"checksum backtrace 0.3.9 (registry+https://github.com/rust-lang/crates.io-index)" = "89a47830402e9981c5c41223151efcced65a0510c13097c769cede7efb34782a"
+"checksum backtrace-sys 0.1.24 (registry+https://github.com/rust-lang/crates.io-index)" = "c66d56ac8dabd07f6aacdaf633f4b8262f5b3601a810a0dcddffd5c22c69daa0"
+"checksum bitflags 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)" = "228047a76f468627ca71776ecdebd732a3423081fcf5125585bcd7c49886ce12"
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+"checksum vec_map 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)" = "05c78687fb1a80548ae3250346c3db86a80a7cdd77bda190189f2d0a0987c81a"
+"checksum version_check 0.9.1 (registry+https://github.com/rust-lang/crates.io-index)" = "078775d0255232fb988e6fccf26ddc9d1ac274299aaedcedce21c6f72cc533ce"
 "checksum void 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)" = "6a02e4885ed3bc0f2de90ea6dd45ebcbb66dacffe03547fadbb0eeae2770887d"
 "checksum walkdir 2.3.1 (registry+https://github.com/rust-lang/crates.io-index)" = "777182bc735b6424e1a57516d35ed72cb8019d85c8c9bf536dccb3445c1a2f7d"
 "checksum wasi 0.9.0+wasi-snapshot-preview1 (registry+https://github.com/rust-lang/crates.io-index)" = "cccddf32554fecc6acb585f82a32a72e28b48f8c4c1883ddfeeeaa96f7d8e519"
@@ -1511,6 +1645,6 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum winapi-x86_64-pc-windows-gnu 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "712e227841d057c1ee1cd2fb22fa7e5a5461ae8e48fa2ca79ec42cfc1931183f"
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-"checksum x11-dl 2.18.5 (registry+https://github.com/rust-lang/crates.io-index)" = "2bf981e3a5b3301209754218f962052d4d9ee97e478f4d26d4a6eced34c1fef8"
+"checksum x11-dl 2.18.3 (registry+https://github.com/rust-lang/crates.io-index)" = "940586acb859ea05c53971ac231685799a7ec1dee66ac0bccc0e6ad96e06b4e3"
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diff --git a/examples/cpu_monitor.rs b/examples/cpu_monitor.rs
index bbe13164a..e923575c6 100644
--- a/examples/cpu_monitor.rs
+++ b/examples/cpu_monitor.rs
@@ -1,47 +1,36 @@
-use docopt::Docopt;
 use std::io;
-use std::process;
+use structopt::StructOpt;
 
-const USAGE: &str = "
-Usage: cpu_monitor [options] <scenario>
-       cpu_monitor --help
-
-A test for monitoring how much CPU usage Rayon consumes under various
-scenarios. This test is intended to be executed interactively, like so:
-
-    cargo run --example cpu_monitor -- tasks_ended
-
-The list of scenarios you can try are as follows:
-
-- tasks_ended: after all tasks have finished, go to sleep
-- task_stall_root: a root task stalls for a very long time
-- task_stall_scope: a task in a scope stalls for a very long time
-
-Options:
-    -h, --help                   Show this message.
-    -d N, --depth N              Control how hard the dummy task works [default: 27]
-";
+#[derive(StructOpt, Debug)]
+pub enum ArgScenario {
+    /// after all tasks have finished, go to sleep
+    TaskEnded,
+    /// a root task stalls for a very long time
+    TaskStallRoot,
+    /// a task in a scope stalls for a very long time
+    TaskStallScope,
+}
 
-#[derive(serde::Deserialize)]
+#[derive(StructOpt, Debug)]
+#[structopt(
+    about = "A test for monitoring how much CPU usage Rayon consumes under various scenarios."
+)]
 pub struct Args {
-    arg_scenario: String,
+    #[structopt(subcommand)]
+    arg_scenario: ArgScenario,
+    /// Control how hard the dummy task works
+    #[structopt(short = "d", long = "depth", default_value = "27")]
     flag_depth: usize,
 }
 
 fn main() {
-    let args: &Args = &Docopt::new(USAGE)
-        .and_then(|d| d.deserialize())
-        .unwrap_or_else(|e| e.exit());
+    use ArgScenario::*;
+    let args: Args = Args::from_args();
 
-    match &args.arg_scenario[..] {
-        "tasks_ended" => tasks_ended(args),
-        "task_stall_root" => task_stall_root(args),
-        "task_stall_scope" => task_stall_scope(args),
-        _ => {
-            println!("unknown scenario: `{}`", args.arg_scenario);
-            println!("try --help");
-            process::exit(1);
-        }
+    match args.arg_scenario {
+        TaskEnded => tasks_ended(&args),
+        TaskStallRoot => task_stall_root(&args),
+        TaskStallScope => task_stall_scope(&args),
     }
 }