Benchmark edge cases better.

lgarron · Jun 6, 2024 · 36f8464 · 36f8464
1 parent 44ad379
commit 36f8464
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Showing 3 changed files with 21 additions and 4 deletions.
diff --git a/src/benchmark/benchmark.ts b/src/benchmark/benchmark.ts
@@ -1,9 +1,21 @@
+const originalGetRandomValues = globalThis.crypto.getRandomValues.bind(
+  globalThis.crypto,
+);
+
+let counter = 0;
+
+globalThis.crypto.getRandomValues = (array) => {
+  counter++;
+  return originalGetRandomValues(array);
+};
+
 import { randomUIntBelow } from "../random-uint-below";
 
 const DEFAULT_NUM_RUNS = 1_000_000;
 const DEFAULT_MAX = 1337;
 
 export function benchmark(options?: { numRuns?: number; max?: number }) {
+  counter = 0;
   const start = performance.now();
   let total = 0;
   const numRuns = options?.numRuns ?? DEFAULT_NUM_RUNS;
@@ -14,7 +26,7 @@ export function benchmark(options?: { numRuns?: number; max?: number }) {
     total += randomUIntBelow(max);
   }
   console.log(
-    `Finished ${numRuns} runs for max ${max} in: ${Math.floor((performance.now() - start) * 1000) / 1000}ms`,
+    `Finished ${numRuns} runs for max ${max} in: ${Math.floor((performance.now() - start) * 1000) / 1000}ms (${counter} calls)`,
   );
   console.log(
     `Mean of generated values (should be ≈${(max - 1) / 2}): ${total / numRuns}`,

diff --git a/src/benchmark/main.ts b/src/benchmark/main.ts
@@ -1,6 +1,11 @@
 import { benchmark } from "./benchmark";
 
 benchmark();
-benchmark({ numRuns: 1_000_000, max: 2 ** 52 });
 benchmark({ numRuns: 1_000_000, max: 7 });
-benchmark({ numRuns: 1_000_000, max: 3 * 2 ** 51 });
+benchmark({ numRuns: 100_000, max: 2 ** 52 - 1 });
+benchmark({ numRuns: 100_000, max: 2 ** 52 });
+benchmark({ numRuns: 100_000, max: 2 ** 52 + 1 });
+benchmark({ numRuns: 100_000, max: 3 * 2 ** 51 });
+benchmark({ numRuns: 100_000, max: 2 ** 53 - 1 });
+benchmark({ numRuns: 100_000, max: (2 ** 53 / 16) * 15 });
+benchmark({ numRuns: 100_000, max: 2 ** 53 });
diff --git a/src/random-uint-below/randomUIntBelow.ts b/src/random-uint-below/randomUIntBelow.ts
@@ -49,7 +49,7 @@ export function randomUIntBelow(max: number): number {
     val = random53BitNumber();
     block = Math.floor(val / max);
     blockMax = block * max;
-    if (blockMax < MAX_JS_PRECISE_INT - max) {
+    if (blockMax <= MAX_JS_PRECISE_INT - max) {
       return val - blockMax;
     }
   }