feat: Collatz conjecture test for rv32im (#769)

toolchain/tests/programs/examples/collatz.rs

@@ -0,0 +1,23 @@
+#![cfg_attr(target_os = "zkvm", no_main)]
+#![cfg_attr(not(feature = "std"), no_std)]
+
+axvm::entry!(main);
+
+pub fn main() {
+    let mut x: u32 = core::hint::black_box(837799);
+    let mut count: u32 = 0;
+
+    while count < 1000 && x != 1 {
+        if x % 2 == 0 {
+            x /= 2;
+        } else {
+            x = 3 * x + 1;
+        }
+        count += 1;
+    }
+
+    // https://en.wikipedia.org/wiki/Collatz_conjecture#Empirical_data
+    if count != 524 {
+        axvm::process::panic();
+    }
+}

toolchain/tests/src/basic_tests.rs

@@ -21,6 +21,14 @@ fn test_rv32i_prove(example_name: &str, min_segments: usize) -> Result<()> {
     Ok(())
 }
 
+#[test_case("collatz", 1)]
+fn test_rv32im_prove(example_name: &str, min_segments: usize) -> Result<()> {
+    let elf = build_example_program(example_name)?;
+    let config = VmConfig::rv32im();
+    air_test_with_min_segments(config, elf, vec![], min_segments);
+    Ok(())
+}
+
 #[test]
 fn test_read_vec_runtime() -> Result<()> {
     let elf = build_example_program("hint")?;