mutation: Use hasFixedSize in sizeInClosedRange

The benchmarks in `//tests/benchmarks` show that biasing the size of
subsets of collections of primitives chosen by the mutator to be small
results in much worse performance than a comparable unstructured fuzz
test.

Before this change, 11 out of 15 runs time out with no run limit, the
other ones result in:

```
{
  "values": [
    11143,
    28128,
    581194,
    4229980
  ],
  "minimum": 11143,
  "maximum": 4229980,
  "average": 1212611.25,
  "median": 304661
}
```

After this change, all runs pass within a limit of 35,000 runs:

```
{
  "values": [
    887,
    1557,
    1889,
    2557,
    3023,
    3346,
    3517,
    6075,
    6613,
    7991,
    9578,
    10850,
    15583,
    23638,
    31046
  ],
  "minimum": 887,
  "maximum": 31046,
  "average": 8543.333333333334,
  "median": 6075
}
```

ExperimentalMutatorComplexProtoFuzzer now takes more runs on Linux, but
still less than on other platforms, which seems to indicate that the
Linux seed just happened to be a lucky choice.

Author: fmeum

.github/workflows/run-all-tests.yml

@@ -42,7 +42,7 @@ jobs:
             extra_bazel_args: "--jvmopt=-Djava.security.manager=allow"
           - os: ubuntu-20.04
             arch: "linux"
-            bazel_args: "//launcher/android:jazzer_android"
+            bazel_args: "//launcher/android:jazzer_android //tests/benchmarks"
             cache: "/home/runner/.cache/bazel-disk"
           - os: macos-12
             arch: "macos-x86_64"

src/main/java/com/code_intelligence/jazzer/mutation/engine/SeededPseudoRandom.java

@@ -252,7 +252,11 @@ private int closedRangeBiasedTowardsSmall(int upperInclusive) {
   @Override
   public int sizeInClosedRange(
       int lowerInclusive, int upperInclusive, boolean elementsHaveFixedSize) {
-    return lowerInclusive + closedRangeBiasedTowardsSmall(upperInclusive - lowerInclusive);
+    if (elementsHaveFixedSize) {
+      return closedRange(lowerInclusive, upperInclusive);
+    } else {
+      return lowerInclusive + closedRangeBiasedTowardsSmall(upperInclusive - lowerInclusive);
+    }
   }
 
   private static double zipf_h(double x) {

tests/BUILD.bazel

@@ -523,13 +523,9 @@ java_fuzz_target_test(
         "--experimental_mutator",
         "--instrumentation_includes=com.example.**",
         "--custom_hook_includes=com.example.**",
-    ] + select({
         # Limit runs to catch regressions in mutator efficiency and speed up test runs.
-        "@platforms//os:linux": ["-runs=400000"],
-        # TODO: Investigate why this test takes far more runs on macOS, with Windows also being
-        #       significantly worse than Linux.
-        "//conditions:default": ["-runs=1200000"],
-    }),
+        "-runs=1200000",
+    ],
     target_class = "com.example.ExperimentalMutatorComplexProtoFuzzer",
     verify_crash_reproducer = False,
     deps = [

tests/benchmarks/BUILD.bazel

@@ -32,7 +32,7 @@ fuzzer_benchmark(
         "--experimental_mutator",
         "-use_value_profile=1",
     ],
-    max_runs = 55000,
+    max_runs = 35000,
     num_seeds = 15,
     target_class = "com.example.StructuredMutatorMazeFuzzer",
     deps = [