danielsun1106 commented on a change in pull request #903: GROOVY-9060: Make the
initial capacity of LinkedHashMap be power of 2…
URL: https://github.com/apache/groovy/pull/903#discussion_r270664227
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File path: src/main/java/org/codehaus/groovy/runtime/InvokerHelper.java
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@@ -396,10 +402,33 @@ public static List createList(Object[] values) {
return answer;
}
+ /**
+ * Get the initial capacity of hash map, which is the closest power of 2
to the entry count.
+ * (SEE
https://stackoverflow.com/questions/8352378/why-does-hashmap-require-that-the-initial-capacity-be-a-power-of-two)
+ *
+ * e.g.
+ * 1: 1
+ * 2: 2
+ * 3: 4
+ * 4: 4
+ * 5: 8
+ * 6: 8
+ * 7: 8
+ * 8: 8
+ * 9: 16
+ * ...
+ *
+ * @param initialEntryCnt the initial entry count
+ * @return the initial capacity
+ */
+ public static int initialCapacity(int initialEntryCnt) {
+ return (int) pow(2, ceil(log(initialEntryCnt) / LN2));
Review comment:
I will tweak the current implementation according to suggestion, which will
be more efficient 😄
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