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Date: Wed, 24 Jun 2009 01:55:07 -0700 (PDT)
From: "Jim Yu (JIRA)" <jira@apache.org>
To: commits@harmony.apache.org
Subject: [jira] Closed: (HARMONY-5853) [classlib][util] Performance
 improvement in Timer
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     [ https://issues.apache.org/jira/browse/HARMONY-5853?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Jim Yu closed HARMONY-5853.
---------------------------


> [classlib][util] Performance improvement in Timer
> -------------------------------------------------
>
>                 Key: HARMONY-5853
>                 URL: https://issues.apache.org/jira/browse/HARMONY-5853
>             Project: Harmony
>          Issue Type: Improvement
>          Components: Classlib
>    Affects Versions: 5.0M6
>            Reporter: Jim Yu
>            Assignee: Sean Qiu
>             Fix For: 5.0M7
>
>         Attachments: HARMONY-5853.diff
>
>
> An performance improvement in Timer by using Binary-Heap intead of Binary Search Tree to manage tasks. 
> The main reason is that the inner class TimerImpl of Timer will launch a separate thread for each Timer. In this thread,
> it will frequently call task = tasks.minimum(), which selects a task with the  minimum 'when' field value from the
> task manager. At present, the task manager's data structure is a Binary Search Tree. It needs to search the tree
> from the root to get the node with the minimum value. The time complexity in worst case is the height of the tree.
> If we use a Binary-Heap instead to manage the tasks, the node with minimum value is always the root. The time
> complexity is O(1). Moreover, the performance of Binary-Heap for node insert and remove operation is also very 
> fast. Though Binary Search Tree  has the advantage of searching a specific node, the search operation is happened
> very seldom in the thread. Therefore, Binary-Heap excels Binary Search Tree in the total performace of task management.

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