Return-Path: X-Original-To: apmail-hadoop-common-dev-archive@www.apache.org Delivered-To: apmail-hadoop-common-dev-archive@www.apache.org Received: from mail.apache.org (hermes.apache.org [140.211.11.3]) by minotaur.apache.org (Postfix) with SMTP id 11AFB17CE5 for ; Mon, 29 Sep 2014 18:47:36 +0000 (UTC) Received: (qmail 84658 invoked by uid 500); 29 Sep 2014 18:47:34 -0000 Delivered-To: apmail-hadoop-common-dev-archive@hadoop.apache.org Received: (qmail 84290 invoked by uid 500); 29 Sep 2014 18:47:34 -0000 Mailing-List: contact common-dev-help@hadoop.apache.org; run by ezmlm Precedence: bulk List-Help: List-Unsubscribe: List-Post: List-Id: Reply-To: common-dev@hadoop.apache.org Delivered-To: mailing list common-dev@hadoop.apache.org Received: (qmail 84073 invoked by uid 99); 29 Sep 2014 18:47:34 -0000 Received: from arcas.apache.org (HELO arcas.apache.org) (140.211.11.28) by apache.org (qpsmtpd/0.29) with ESMTP; Mon, 29 Sep 2014 18:47:34 +0000 Date: Mon, 29 Sep 2014 18:47:34 +0000 (UTC) From: "Luke Lu (JIRA)" To: common-dev@hadoop.apache.org Message-ID: In-Reply-To: References: Subject: [jira] [Created] (HADOOP-11152) Better random number generator MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-JIRA-FingerPrint: 30527f35849b9dde25b450d4833f0394 Luke Lu created HADOOP-11152: -------------------------------- Summary: Better random number generator Key: HADOOP-11152 URL: https://issues.apache.org/jira/browse/HADOOP-11152 Project: Hadoop Common Issue Type: Improvement Reporter: Luke Lu HDFS-7122 showed that naive ThreadLocal usage of simple LCG based j.u.Random creates unacceptable distribution of random numbers for block placement. Similarly, ThreadLocalRandom in java 7 (same static thread local with synchronized methods overridden) has the same problem. "Better" is defined as better quality and faster than j.u.Random (which is already much faster (20x) than SecureRandom). People (e.g. Numerical Recipes) have shown that by combining LCG and XORShift we can have a better fast RNG. It'd be worthwhile to investigate a thread local version of these "better" RNG. -- This message was sent by Atlassian JIRA (v6.3.4#6332)