web: page figures use goFixed

web/src/gofixed.js

@@ -0,0 +1,16 @@
+// goFixed is strconv.FormatFloat(v, 'f', digits, 64). toFixed already rounds
+// the exact binary value; the one difference is an exact tie, which toFixed
+// takes away from zero and Go takes to even. A tie is a multiple of
+// 2^-(digits+1), and that test is exact (a power-of-two scale).
+//
+// It lives here so the page chrome and the run route can both print with it.
+// page.js must not import run.js: run.js imports the page.
+export function goFixed(v, digits) {
+  const m = 10 ** digits;
+  const x = v * m;
+  if (Number.isInteger(v * 2 ** (digits + 1)) && !Number.isInteger(x)) {
+    const f = Math.floor(x);
+    return ((f % 2 === 0 ? f : f + 1) / m).toFixed(digits);
+  }
+  return v.toFixed(digits);
+}

web/src/page.js

@@ -1,3 +1,5 @@
+import { goFixed } from "./gofixed.js";
+
 // The chrome every page shares.
 //
 // One stylesheet, inline, because the pages are small and a published run
@@ -222,5 +224,7 @@ export function esc(s) {
 // `?`; never print a default you did not observe).
 export function fmt(n) {
   if (!n) return "?";
-  return n >= 100 ? n.toFixed(0) : n.toFixed(1);
+  // The card's formatRate. goFixed is the tie rule; toFixed would print the
+  // other way on an exact half.
+  return n >= 100 ? goFixed(n, 0) : goFixed(n, 1);
 }

web/src/run.js

@@ -10,6 +10,7 @@
 // a door — the id is the secret (§9.3).
 
 import { avatarPath } from "./author.js";
+import { goFixed } from "./gofixed.js";
 import { fail, json } from "./http.js";
 import { esc, fmt, head, layout } from "./page.js";
 
@@ -659,20 +660,6 @@ function formatProbeMs(v) {
   return `${goFixed(v, 0)} ms`;
 }
 
-// goFixed is strconv.FormatFloat(v, 'f', digits, 64). toFixed already rounds
-// the exact binary value; the one difference is an exact tie, which toFixed
-// takes away from zero and Go takes to even. A tie is a multiple of
-// 2^-(digits+1), and that test is exact (a power-of-two scale).
-export function goFixed(v, digits) {
-  const m = 10 ** digits;
-  const x = v * m;
-  if (Number.isInteger(v * 2 ** (digits + 1)) && !Number.isInteger(x)) {
-    const f = Math.floor(x);
-    return ((f % 2 === 0 ? f : f + 1) / m).toFixed(digits);
-  }
-  return v.toFixed(digits);
-}
-
 // memoryRow is the card's MEMORY lines that the index carries, in one cell:
 // "GPU0 10.4/12.0 GiB · host RSS 11.6 GiB (file 11.1 / anon 0.2)". Each
 // gpu_mem entry is "GPUn used/total GiB", or "GPUn used GiB" when the

web/test/gofixed.test.mjs

@@ -6,7 +6,8 @@
 import assert from "node:assert/strict";
 import test from "node:test";
 
-import { goFixed } from "../src/run.js";
+import { fmt } from "../src/page.js";
+import { goFixed } from "../src/gofixed.js";
 
 test("an exact tie rounds to even, as Go does", () => {
   assert.equal(goFixed(0.25, 1), "0.2");
@@ -16,6 +17,13 @@ test("an exact tie rounds to even, as Go does", () => {
   assert.equal(goFixed(-0.25, 1), "-0.2");
 });
 
+test("fmt uses that tie rule for the figures the page shares with the card", () => {
+  assert.equal(fmt(0.25), "0.2");
+  assert.equal(fmt(0.75), "0.8");
+  assert.equal(fmt(150.5), "150");
+  assert.equal(fmt(0), "?");
+});
+
 test("a value that only looks like a tie rounds by its exact value", () => {
   // 0.15 and 1.45 are stored just under the tie (0.1499…, 1.4499…): Go prints 0.1 and 1.4.
   assert.equal(goFixed(0.15, 1), "0.1");