From 25d7f0d8b28de5941d8d98e4a3cec43d6b2e7020 Mon Sep 17 00:00:00 2001
From: "Christoph J. Scherr" <Christoph.Scherr@newtec.de>
Date: Mon, 12 Aug 2024 13:21:55 +0200
Subject: [PATCH] revsqrt stuff for PA2

---
 members/revsqrt/Cargo.toml                    |  6 +-
 .../tests/features/book/revsqrt-demo.feature  | 33 ++++++++
 members/revsqrt/tests/revsqrt-demo.rs         | 82 +++++++++++++++++++
 3 files changed, 120 insertions(+), 1 deletion(-)
 create mode 100644 members/revsqrt/tests/features/book/revsqrt-demo.feature
 create mode 100644 members/revsqrt/tests/revsqrt-demo.rs

diff --git a/members/revsqrt/Cargo.toml b/members/revsqrt/Cargo.toml
index b654fb9..4b70459 100644
--- a/members/revsqrt/Cargo.toml
+++ b/members/revsqrt/Cargo.toml
@@ -12,7 +12,7 @@ rand = "0.8.5"
 
 [[bench]]
 name = "rsqrt-bench"
-harness = false 	# disable standard harness
+harness = false      # disable standard harness
 
 [lib]
 name = "revsqrt"
@@ -26,6 +26,10 @@ path = "src/main.rs"
 name = "revsqrt"
 harness = false  # allows Cucumber to print output instead of libtest
 
+[[test]]
+name = "revsqrt-demo"
+harness = false       # allows Cucumber to print output instead of libtest
+
 [[test]]
 name = "basic-revsqrt"
 harness = true
diff --git a/members/revsqrt/tests/features/book/revsqrt-demo.feature b/members/revsqrt/tests/features/book/revsqrt-demo.feature
new file mode 100644
index 0000000..b9c4f02
--- /dev/null
+++ b/members/revsqrt/tests/features/book/revsqrt-demo.feature
@@ -0,0 +1,33 @@
+Feature: inverted square root calculation
+
+  Scenario: fast inverted sqrt is about the same as the regular inverted sqrt
+    Given a number
+    When we calculate the inverted square root of it using the fast inverted square root algorithm
+    Then the result is about the same as if we calculate it normally
+
+  Scenario: Can the fast inverted sqrt be calculated?
+    Given a number
+    When we calculate the inverted square root of it using the fast inverted square root algorithm
+    Then the result can be calculated
+
+  Scenario: Can the regular inverted sqrt be calculated?
+    Given a number
+    When we calculate the inverted square root of it normally
+    Then the result can be calculated
+
+  Scenario: Calculate regular inverted sqrt with specific numbers
+    Given the number n
+      | 1            |
+      | 1.1          |
+      | 100          |
+      | 1337         |
+      | 123.45678900 |
+      | 1337.1337    |
+    When we calculate the inverted square root of it normally
+    Then the result is m
+      | 1                    |
+      | 0.9534625892455922   |
+      | 0.1                  |
+      | 0.02734854943722097  |
+      | 0.0900000004095      |
+      | 0.027347182112297627 |
diff --git a/members/revsqrt/tests/revsqrt-demo.rs b/members/revsqrt/tests/revsqrt-demo.rs
new file mode 100644
index 0000000..7e9780f
--- /dev/null
+++ b/members/revsqrt/tests/revsqrt-demo.rs
@@ -0,0 +1,82 @@
+use cucumber::{gherkin::Step, given, then, when, World};
+
+/// stores the current information for each scenario
+#[derive(Debug, Default, World)]
+struct NumWorld {
+    numbers: Vec<(f32, f32)>,
+}
+
+/// is n about the same as m?
+///
+/// This is actually not so easy! How do you measure *about same*ness?
+/// Also, I don't think it is transitive, as 1 ≈ 1.1 ≈ 1.2 ≈ 1.3 ≈ ... ≈ 2 ≈ ... ≈ 3 ≈ ... ≈ infinity
+#[inline]
+fn about_same(n: f32, m: f32) -> bool {
+    (n - m).abs() <= calc_gate(n, m)
+}
+
+#[inline]
+fn calc_gate(n: f32, m: f32) -> f32 {
+    0.01 + ((n.abs().sqrt().min(m.abs().sqrt())).abs() / 10f32)
+}
+
+#[given(regex = r"the number n")]
+async fn give_specific_number(world: &mut NumWorld, step: &Step) {
+    if let Some(table) = step.table.as_ref() {
+        for row in table.rows.iter() {
+            let n = row[0].parse::<f32>().unwrap();
+            world.numbers.push((n, f32::NAN));
+        }
+    }
+}
+
+#[given("a number")]
+async fn give_rand_number(world: &mut NumWorld) {
+    world.numbers.push(rand::random());
+}
+
+#[when("we calculate the inverted square root of it using the fast inverted square root algorithm")]
+async fn calc_fast_inv_sqrt(world: &mut NumWorld) {
+    for pair in &mut world.numbers {
+        pair.1 = revsqrt::fast_inverse_sqrt(pair.0)
+    }
+}
+
+#[when("we calculate the inverted square root of it normally")]
+async fn calc_reg_inv_sqrt(world: &mut NumWorld) {
+    for pair in &mut world.numbers {
+        pair.1 = revsqrt::regular_inverse_sqrt(pair.0)
+    }
+}
+
+#[then("the result can be calculated")]
+async fn can_be_calculated(world: &mut NumWorld) {
+    for pair in &mut world.numbers {
+        assert!(!pair.0.is_nan());
+        assert!(!pair.1.is_nan());
+        assert!(pair.0.is_finite());
+        assert!(pair.1.is_finite());
+    }
+}
+
+#[then("the result is about the same as if we calculate it normally")]
+async fn comp_result_with_normal(world: &mut NumWorld) {
+    for pair in &mut world.numbers {
+        assert!(about_same(pair.1, revsqrt::regular_inverse_sqrt(pair.0)));
+    }
+}
+
+#[then(regex = r"the result is m")]
+async fn result_is(world: &mut NumWorld, step: &Step) {
+    if let Some(table) = step.table.as_ref() {
+        for (row, i) in std::iter::zip(table.rows.iter(), 0..table.rows.len() - 1) {
+            let m = row[0].parse::<f32>().unwrap();
+            assert_eq!(world.numbers[i].1, m);
+        }
+    }
+}
+
+#[tokio::main]
+async fn main() {
+    NumWorld::run("tests/features/book/revsqrt-demo.feature").await;
+}