Subject: REFEREE'S REPORT: C517: Automatic Determination of Matrix-Blocks From: Ulrich Ruede Date: Tue, 25 Sep 2001 12:37:11 +0200 (CEST) To: gcf@indiana.edu X-UIDL: 23fc3c9dc7110000 X-Mozilla-Status: 0001 X-Mozilla-Status2: 00000000 Received: by mailer.csit.fsu.edu (mbox gcfpc) (with Cubic Circle's cucipop (v1.31 1998/05/13) Sun Oct 14 21:55:50 2001) X-From_: fox@mailer.csit.fsu.edu Sun Oct 14 21:49:40 2001 Return-Path: Delivered-To: gcfpc@csit.fsu.edu Received: from dirac.csit.fsu.edu (dirac.csit.fsu.edu [144.174.128.44]) by mailer.csit.fsu.edu (Postfix) with ESMTP id 9FF7D23A05 for ; Sun, 14 Oct 2001 21:49:40 -0400 (EDT) Received: from localhost by dirac.csit.fsu.edu (AIX4.2/UCB 8.7) id VAA86638; Sun, 14 Oct 2001 21:49:39 -0400 (EDT) Resent-Message-Id: <200110150149.VAA86638@dirac.csit.fsu.edu> Replied: Tue, 25 Sep 2001 07:41:54 -0400 Replied: Ulrich Ruede Delivered-To: fox@csit.fsu.edu Received: from mask.uits.indiana.edu (mask.uits.indiana.edu [129.79.6.184]) by mailer.csit.fsu.edu (Postfix) with ESMTP id B14E723A20 for ; Tue, 25 Sep 2001 06:36:58 -0400 (EDT) Received: from fauia10.informatik.uni-erlangen.de (fauia10.informatik.uni-erlangen.de [131.188.67.10]) by mask.uits.indiana.edu (8.10.1/8.10.1/IUPO) with ESMTP id f8PAYqc09357 for ; Tue, 25 Sep 2001 05:34:52 -0500 (EST) Received: from fauia19.informatik.uni-erlangen.de (fauia19.informatik.uni-erlangen.de [131.188.67.19]) by fauia10.informatik.uni-erlangen.de (Postfix) with ESMTP id E0DE43CF00 for ; Tue, 25 Sep 2001 12:37:11 +0200 (CEST) Received: from localhost (ruede@localhost) by fauia19.informatik.uni-erlangen.de (8.9.3/8.9.3/SuSE Linux 8.9.3-0.1) with ESMTP id MAA18704 for ; Tue, 25 Sep 2001 12:37:11 +0200 Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Resent-To: Geoffrey Fox Resent-Date: Sun, 14 Oct 2001 21:49:39 -0400 Resent-From: Geoffrey Fox Referee's Report for "Concurrency and Computation:Practice and Experience" Manuscript: C517: Automatic Determination of Matrix-Blocks by: Victor Eijkhout D: Referee Comments (For Editor Only) I do not think the paper should be published in this form. E: Referee Comments (For Author and Editor) This paper deals with algorithms for the automatic determination of structure in sparse matrices. Many - especially very large sparse matrices arise from the discretization of partial differential equations and therefore have an inherent structure which can be used in algorithms like domain decomposition. Once the matric has been constructed, the original structure is lost. This paper deals with algorithms which can reconstruct this information given only the matrix, but no information on where the matrix comes from. This is potentially an important and useful problem. Though a good interface between PDE and solver should probably pass the extra information (like grid structure, blocks, subdomains, etc) to the solver, in many realistic applications this information is not available and a black box solver must be used given only the matrix and no extra information. So the topic is promising, but unfortunately, the 6 page paper itself is quite disappointing. The algorithms are described poorly. Except a few code fragments the description of the algorithms remains informal and vague. I have not been able to understand what the algorithms do in detail. The hints at their parallelization are unintelligible. Even worse, there is hardly any attempt to discuss the properties of these algorithms. What is the complexity and how does it depend on the specific matrices considered? What role play the data structures for the matrices? Of course it would also be interesting to study the the quality of the automatically constructed partitions and compare them to those obtained manually for the same problem. At least for model problems, as they arise in typical 2D and 3D grid problems, the algorithmic complexity of the algorithms could be analyzed. In that case, the type of partitions could be compared to those from typical grid partitioning approaches. Such a more detailed analysis would indeed be interesting, but the current paper does too little in that direction. .