feat(tvix/eval/benches): benchmark intersectAttrs

Change-Id: If5da2c4022758900a0d0167835ff7a61613e05a4
Reviewed-on: https://cl.snix.dev/c/snix/+/30373
Tested-by: besadii
Reviewed-by: Florian Klink <flokli@flokli.de>

snix/eval/benches/eval.rs

@@ -38,5 +38,60 @@ fn eval_merge_attrs(c: &mut Criterion) {
     });
 }
 
-criterion_group!(benches, eval_literals, eval_merge_attrs);
+fn eval_intersect_attrs(c: &mut Criterion) {
+    c.bench_function("intersect small attrs", |b| {
+        b.iter(|| {
+            interpret(black_box(
+                "builtins.intersectAttrs { a = 1; b = 2; } { c = 3; }",
+            ));
+        })
+    });
+
+    c.bench_function("intersect large attrs with small attrs", |b| {
+        let large_attrs = format!(
+            "{{{}}}",
+            (0..10000).map(|n| format!("a{n} = {n};")).join(" ")
+        );
+        let expr = format!("builtins.intersectAttrs {large_attrs} {{ c = 3; }}");
+        b.iter(move || {
+            interpret(black_box(&expr));
+        })
+    });
+
+    c.bench_function("intersect large attrs with large attrs", |b| {
+        // the intersection is 2n=3m, which is about ~⅓ of the union, and ~¼ of the elements < 2*1e4
+
+        let left_attrs = format!(
+            "{{{}}}",
+            (0..10000)
+                .map(|n| {
+                    let i = 2 * n;
+                    format!("a{i} = {i};")
+                })
+                .join(" ")
+        );
+
+        let right_attrs = format!(
+            "{{{}}}",
+            (0..10000)
+                .map(|m| {
+                    let j = 3 * m;
+                    format!("a{j} = {j};")
+                })
+                .join(" ")
+        );
+
+        let expr = format!("builtins.intersectAttrs {left_attrs} {right_attrs}");
+        b.iter(move || {
+            interpret(black_box(&expr));
+        })
+    });
+}
+
+criterion_group!(
+    benches,
+    eval_literals,
+    eval_merge_attrs,
+    eval_intersect_attrs
+);
 criterion_main!(benches);