Include camera scan count in validation

Also adds a `block_meal_count` parameter which determines the number
of meals that represents a block of progress. The size of the block
determines the number of camera scans, which the benchmark validates.

benchmarks/scala-stm/src/main/scala/org/renaissance/scala/stm/Philosophers.scala

@@ -19,7 +19,13 @@ import org.renaissance.License
   defaultValue = "500000",
   summary = "Number of meals consumed by each philosopher thread"
 )
-@Configuration(name = "test", settings = Array("meal_count = 500"))
+@Parameter(
+  name = "block_meal_count",
+  defaultValue = "4096",
+  summary =
+    "Number of meals representing a block of progress. Determines determines the frequency of camera scans. Must be a power of two."
+)
+@Configuration(name = "test", settings = Array("meal_count = 500", "block_meal_count = 8"))
 @Configuration(name = "jmh")
 final class Philosophers extends Benchmark {
 
@@ -28,17 +34,33 @@ final class Philosophers extends Benchmark {
 
   private var threadCountParam: Int = _
 
+  /** Number of meals consumed by each Philosopher thread. */
+  private var mealCountParam: Int = _
+
   /**
-   * Number of meals consumed by each Philosopher thread.
+   * Number of meals representing a block of progress which determines
+   * the frequency of camera scans. Must be power of two to enable
+   * efficient checking.
    */
-  private var mealCountParam: Int = _
+  private var blockMealCountParam: Int = _
 
   override def setUpBeforeAll(c: BenchmarkContext): Unit = {
+    def isPowerOfTwo(n: Int): Boolean = if (n <= 0) false else (n & (n - 1)) == 0
+
     threadCountParam = c.parameter("thread_count").toPositiveInteger
     mealCountParam = c.parameter("meal_count").toPositiveInteger
+
+    blockMealCountParam = c.parameter("block_meal_count").toPositiveInteger
+    if (!isPowerOfTwo(blockMealCountParam)) {
+      throw new IllegalArgumentException(
+        s"the 'block_meal_count' parameter is not a power of two: $blockMealCountParam"
+      )
+    }
   }
 
-  private def validate(forkOwners: Seq[Option[String]], mealsEaten: Seq[Int]): Unit = {
+  private def validate(result: (Seq[Option[String]], Seq[Int], Int)): Unit = {
+    val (forkOwners, mealsEaten, scanCount) = result
+
     // All forks should be available, i.e., not owned by anyone.
     for (i <- 0 until threadCountParam) {
       Assert.assertEquals(None, forkOwners(i), s"owner of fork %i")
@@ -48,13 +70,21 @@ final class Philosophers extends Benchmark {
     for (i <- 0 until threadCountParam) {
       Assert.assertEquals(mealCountParam, mealsEaten(i), s"meals eaten by philosopher $i")
     }
+
+    // The camera performed the expected number of scans.
+    val expectedScanCount = mealCountParam / blockMealCountParam
+    Assert.assertEquals(expectedScanCount, scanCount, "camera scans")
   }
 
   override def run(c: BenchmarkContext): BenchmarkResult = {
-    val (forkOwners, mealsEaten) = RealityShowPhilosophers.run(mealCountParam, threadCountParam)
+    val result = RealityShowPhilosophers.run(
+      mealCountParam,
+      threadCountParam,
+      blockMealCountParam
+    )
 
     () => {
-      validate(forkOwners, mealsEaten)
+      validate(result)
     }
   }
 

benchmarks/scala-stm/src/main/scala/org/renaissance/scala/stm/RealityShowPhilosophers.scala

@@ -160,9 +160,13 @@ object RealityShowPhilosophers {
     }
   }
 
-  def run(mealCount: Int, philosopherCount: Int): (Seq[Option[String]], Seq[Int]) = {
+  def run(
+    mealCount: Int,
+    philosopherCount: Int,
+    blockMealCount: Int
+  ): (Seq[Option[String]], Seq[Int], Int) = {
     val forks = Array.tabulate(philosopherCount) { i => new Fork(s"fork-$i") }
-    val controller = new CameraController(philosopherCount, 1 << 12)
+    val controller = new CameraController(philosopherCount, blockMealCount)
     val philosophers = Array.tabulate(philosopherCount) { i =>
       new PhilosopherThread(
         s"philosopher-$i",
@@ -184,6 +188,7 @@ object RealityShowPhilosophers {
     camera.join()
 
     // Collect fork owners and meals eaten for validation.
-    camera.stateSnapshot
+    val (forkOwners, mealsEaten) = camera.stateSnapshot
+    (forkOwners, mealsEaten, camera.images.length)
   }
 }