[8_13] improve performance when calculating hash of string

XmacsLabs · Jun 8, 2024 · 85ba510 · 85ba510
1 parent d933682
commit 85ba510
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Showing 2 changed files with 11 additions and 3 deletions.
diff --git a/Kernel/Types/string.cpp b/Kernel/Types/string.cpp
@@ -221,10 +221,10 @@ operator<= (string s1, string s2) {
 
 int
 hash (string s) {
-  int i, h= 0, n= N (s);
-  for (i= 0; i < n; i++) {
+  int h= 0;
+  for (char ch : s) {
     h= (h << 9) + (h >> 23);
-    h= h + ((int) s[i]);
+    h= h + ((int) ch);
   }
   return h;
 }

diff --git a/bench/Kernel/Types/string_bench.cpp b/bench/Kernel/Types/string_bench.cpp
@@ -52,6 +52,14 @@ main () {
     static string a ("abc"), b ("de");
     a << b;
   });
+  bench.run ("hash of string", [&] {
+    static string a ("accde");
+    hash (a);
+  });
+  bench.run ("hash of larger string", [&] {
+    static string a ("compare larger string ,compute hash of LARGER string");
+    hash (a);
+  });
   bench.run ("is quoted", [&] {
     static string a ("H\"ello TeXmacs\"");
     is_quoted (a);