GitHub user mengxr opened a pull request: https://github.com/apache/spark/pull/131
[SPARK-1237, 1238] Improve the computation of YtY for implicit ALS Computing YtY can be implemented using BLAS's DSPR operations instead of generating y_i y_i^T and then combining them. The latter generates many k-by-k matrices. On the movielens data, this change improves the performance by 10-20%. The algorithm remains the same, verified by computing RMSE on the movielens data. To compare the results, I also added an option to set a random seed in ALS. JIRA: 1. https://spark-project.atlassian.net/browse/SPARK-1237 2. https://spark-project.atlassian.net/browse/SPARK-1238 You can merge this pull request into a Git repository by running: $ git pull https://github.com/mengxr/spark als Alternatively you can review and apply these changes as the patch at: https://github.com/apache/spark/pull/131.patch To close this pull request, make a commit to your master/trunk branch with (at least) the following in the commit message: This closes #131 ---- commit 200bef0c18bc1309c83366be94009eadd460befc Author: Xiangrui Meng <m...@databricks.com> Date: 2014-03-12T21:06:05Z optimize computeYtY and updateBlock commit 4c7cde24b7973f881431642c21e8820aa540b340 Author: Xiangrui Meng <m...@databricks.com> Date: 2014-03-13T00:30:12Z allow specifying a random seed in ALS commit 2fc164163656eeffba4b2bd3dc746b117c15de22 Author: Xiangrui Meng <m...@databricks.com> Date: 2014-03-13T00:32:24Z remove commented code commit d984623d1702a89cf948e55ce84153eb59c97ebd Author: Xiangrui Meng <m...@databricks.com> Date: 2014-03-13T00:50:35Z minor changes ---- --- If your project is set up for it, you can reply to this email and have your reply appear on GitHub as well. If your project does not have this feature enabled and wishes so, or if the feature is enabled but not working, please contact infrastructure at infrastruct...@apache.org or file a JIRA ticket with INFRA. ---