Hi, I was considering an issue not discussed in Pregel paper. One interesting thing about MapReduce is that the memory limit for each job in a cluster node is the number of task assigned to that node * the memory allocated by each task (plus of course the framework overhead). The input data is iteratively loaded (and kind of emitted too) from storage and doesn't need to be kept in memory or loaded together in advance.
In Pregel, to me, it looks like the whole graph has to fit in memory among the cluster nodes. As it is somehow stateful and doesn't have an iterative job-job nature as MapReduce, at the beginning of the job all the vertices and their data have to be loaded into the cluster (and kept in memory). So the question is: if i want to run Pagerank over my graph, do I need to be able to store the whole graph in memory? Thanks! -- Claudio Martella Digital Technologies Unit Research & Development - Analyst TIS innovation park Via Siemens 19 | Siemensstr. 19 39100 Bolzano | 39100 Bozen Tel. +39 0471 068 123 Fax +39 0471 068 129 [email protected] http://www.tis.bz.it Short information regarding use of personal data. According to Section 13 of Italian Legislative Decree no. 196 of 30 June 2003, we inform you that we process your personal data in order to fulfil contractual and fiscal obligations and also to send you information regarding our services and events. Your personal data are processed with and without electronic means and by respecting data subjects' rights, fundamental freedoms and dignity, particularly with regard to confidentiality, personal identity and the right to personal data protection. At any time and without formalities you can write an e-mail to [email protected] in order to object the processing of your personal data for the purpose of sending advertising materials and also to exercise the right to access personal data and other rights referred to in Section 7 of Decree 196/2003. The data controller is TIS Techno Innovation Alto Adige, Siemens Street n. 19, Bolzano. You can find the complete information on the web site www.tis.bz.it.
