CLDR-17327 speedup VoteResolver's transcript

- skip String.format when unneeded
- defer all transcript operations until needed

measured as between a 5 and 10x speedup

tools/cldr-code/src/main/java/org/unicode/cldr/util/DeferredTranscript.java

@@ -0,0 +1,72 @@
+package org.unicode.cldr.util;
+
+import com.google.common.base.Supplier;
+import com.google.common.base.Suppliers;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.stream.Collectors;
+
+/**
+ * lazily-calculates the transcript. Thread safe to call get() multiple times once commit() is
+ * called and before clear() is called.
+ */
+public class DeferredTranscript implements Supplier<String> {
+
+    private final class FormatEntry {
+        public final CharSequence fmt;
+        public final Object[] args;
+
+        public FormatEntry(String fmt, Object[] args) {
+            this.fmt = fmt;
+            this.args = args;
+        }
+
+        public final CharSequence format() {
+            if (args == null || args.length == 0) {
+                return fmt;
+            } else {
+                return String.format(fmt.toString(), args);
+            }
+        }
+    }
+
+    public DeferredTranscript() {
+        clear();
+    }
+
+    private Supplier<String> delegate = null;
+    private List<FormatEntry> formats;
+
+    /** reset this transcript so it can be used again. */
+    public void clear() {
+        // the delegate only calculates the value once, the first time it is accessed.
+        delegate =
+                Suppliers.memoize(
+                        new Supplier<String>() {
+
+                            @Override
+                            public String get() {
+                                return formats.stream()
+                                        .map(FormatEntry::format)
+                                        .collect(Collectors.joining("\n"));
+                            }
+                        });
+        formats = new LinkedList<>();
+    }
+
+    @Override
+    public final String get() {
+        return delegate.get();
+    }
+
+    /**
+     * Add a formatted entry. Will be ignored if get() has been called since clear()
+     *
+     * @param fmt the string or pattern string
+     * @param args if non-null, arguments to String.format()
+     */
+    final DeferredTranscript add(String fmt, Object... args) {
+        formats.add(new FormatEntry(fmt, args));
+        return this;
+    }
+}

tools/cldr-code/src/main/java/org/unicode/cldr/util/VoteResolver.java

@@ -64,19 +64,23 @@ public VoteResolver(VoterInfoList vil) {
     private static final boolean DEBUG = false;
 
     /** This enables a prose discussion of the voting process. */
-    private StringBuilder transcript = null;
+    private DeferredTranscript transcript = null;
 
     public void enableTranscript() {
         if (transcript == null) {
-            transcript = new StringBuilder();
+            transcript = new DeferredTranscript();
         }
     }
 
+    public void disableTranscript() {
+        transcript = null;
+    }
+
     public String getTranscript() {
         if (transcript == null) {
             return null;
         } else {
-            return transcript.toString();
+            return transcript.get();
         }
     }
 
@@ -86,14 +90,10 @@ public String getTranscript() {
      * @param fmt
      * @param args
      */
-    private void annotateTranscript(String fmt, Object... args) {
-        if (DEBUG) {
-            System.out.println("Transcript: " + String.format(fmt, args));
-        }
-        if (transcript == null) {
-            return;
+    private final void annotateTranscript(String fmt, Object... args) {
+        if (transcript != null) {
+            transcript.add(fmt, args);
         }
-        transcript.append(String.format(fmt, args)).append("\n");
     }
 
     /**
@@ -617,7 +617,8 @@ public void clear() {
             baileyValue = null;
             baileySet = false;
             if (transcript != null) {
-                transcript = new StringBuilder();
+                // there was a transcript before, so retain it
+                transcript = new DeferredTranscript();
             }
         }
 
@@ -996,7 +997,7 @@ public void clear() {
         nValue = null;
 
         if (transcript != null) {
-            transcript.setLength(0);
+            transcript.clear();
         }
     }
 

tools/cldr-code/src/test/java/org/unicode/cldr/util/TestDeferredTranscript.java

@@ -0,0 +1,60 @@
+package org.unicode.cldr.util;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
+
+public class TestDeferredTranscript {
+    @Test
+    public void TestBasic() {
+        DeferredTranscript dt = new DeferredTranscript();
+
+        dt.clear();
+
+        assertEquals("", dt.get());
+        assertEquals("", dt.get());
+        dt.clear();
+        dt.add("Hello");
+        assertEquals("Hello", dt.get());
+        // all of these are ignored, we've already committed the output.
+        dt.add("Hello");
+        dt.add("Hello");
+        dt.add("Hello");
+        dt.add("Goodbye %d times", 999);
+        assertEquals("Hello", dt.get());
+        dt.clear();
+        dt.add("Hello");
+        dt.add("Hello");
+        assertEquals("Hello\nHello", dt.get());
+        assertEquals("Hello\nHello", dt.get());
+        dt.clear();
+        assertEquals("", dt.get());
+        dt.clear();
+        dt.add("You have %d problems.", 0);
+        dt.add("Thanks");
+        assertEquals("You have 0 problems.\nThanks", dt.get());
+        dt.add("Thanks");
+        assertEquals("You have 0 problems.\nThanks", dt.get());
+    }
+
+    @ParameterizedTest
+    @ValueSource(booleans = {false, true})
+    public void TestPerf(boolean doGet) {
+        DeferredTranscript dt = new DeferredTranscript();
+        for (int i = 0; i < 100000; i++) {
+            dt.add("Now you have %d problem(s).", i);
+        }
+        // 1M iterations:  2.3 seconds without get(), 10 seconds with
+        if (doGet) {
+            // if doGet is false, the above code is faster.
+            // defer the formatting
+            final String s0 = dt.get();
+            assertNotNull(s0);
+            final String s1 = dt.get();
+            assertEquals(s0, s1);
+        }
+    }
+}

tools/cldr-code/src/test/java/org/unicode/cldr/util/TestVoteResolver.java

@@ -7,6 +7,8 @@
 import com.ibm.icu.util.Output;
 import java.util.Date;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
 import org.unicode.cldr.unittest.TestUtilities;
 import org.unicode.cldr.util.VoteResolver.Status;
 
@@ -46,6 +48,37 @@ void testDisputed() {
                                 vr.getStatusForOrganization(Organization.google)));
     }
 
+    @ParameterizedTest
+    @ValueSource(booleans = {false, true})
+    public void testPerf(boolean doGet) {
+        final VoteResolver<String> vr = getStringResolver();
+        vr.enableTranscript();
+
+        for (int i = 0; i < 100; i++) {
+            vr.clear();
+            vr.setLocale(
+                    CLDRLocale.getInstance("fr"), null); // NB: pathHeader is needed for annotations
+            vr.setBaseline("bafut", Status.unconfirmed);
+            vr.setBaileyValue("bfd");
+            vr.add("bambara", TestUtilities.TestUser.appleV.voterId);
+            vr.add("bafia", TestUtilities.TestUser.googleV.voterId);
+            vr.add("bassa", TestUtilities.TestUser.googleV2.voterId);
+            vr.add("bafut", TestUtilities.TestUser.unaffiliatedS.voterId);
+
+            assertAll(
+                    "Verify the outcome",
+                    () -> assertEquals("bambara", vr.getWinningValue()),
+                    () -> assertEquals(Status.provisional, vr.getWinningStatus()));
+
+            // about 10x faster without calling get()
+            if (doGet) {
+                assertTrue(
+                        vr.getTranscript().contains("earlier than 'bassa'"),
+                        () -> "Transcript did not match expectations:\n" + vr.getTranscript());
+            }
+        }
+    }
+
     @Test
     void testExplanations() {
         // Example from https://st.unicode.org/cldr-apps/v#/fr/Languages_A_D/54dc38b9b6c86cac