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2 * README for IBM Visualization Data Explorer for Symetric Multiprocessors
7 The information contained in this file consists of hints for using the
8 Data Explorer SMP for symmetric multiprocessors.
13 To go directly to an item, search for the item number beginning
14 at the left margin.
16 1. The Partition module
17 2. Partitioning an already-partitioned field
18 3. The default amount of memory used
19 4. The default number of processors used
20 5. The difference between SMP and distributed
25 1. The Partition module
27 With Data Explorer SMP, the Partition module should be used to
28 create a composite field from the imported data.
29 Only if the data set is partitioned
30 will Data Explorer SMP exploit the multiple processors available.
31 Note that you can run partitioned data equally well on both
32 uniprocessor and multiprocessor machines.
34 2. Partitioning an already-partitioned field
36 Once a field is partitioned it will not be repartitioned if it
37 is passed through the Partition module again. Thus to maximize
38 the use of the available processors, you may want
39 to increase the number of partitions (the "n" paramter for
40 Partition) from the default value if you will be operating on
41 only a subset of the data later on. Note however, that over-partitioning
42 a field leads to extra overhead.
44 3. The default amount of memory used
46 By default on a MP machine, less memory will be used than on
47 a UP machine. This is under the assumption that other users
48 may be more likely to be using an MP machine. The amount of
49 memory used can be changed with the -memory command line option
50 to dx. Usage("memory",0) will show you how much memory is being
53 4. The default number of processors used
55 For an MP machine, if the number of processors (n) is 4 or greater,
56 the default number of processors used is n/2, rounded down. If the
57 number of processors is 2 or 3, then the default number of processors
58 used is 2. The number of processors used can be changed with the
59 -processors command line option to dx.
61 5. The difference between SMP and distributed
63 When you run parallel on an SMP machine, intramodule parallelism
64 is used. For example, the Isosurface module will operate in
65 parallel on different portions of a partitioned field. When
66 you use the distributed method of execution, different modules
67 run on different machines; for example, Isosurface might be
68 running on one machine while MapToPlane is running on another.
69 There is overhead involved with using distributed computation, as
70 the data must be transferred between machines.
75 The following trademarks apply to this information:
77 IBM is a registered trademark of International Business Machines Corporation.
78 IBM Visualization Data Explorer is a registered trademark of International
79 Business Machines Corporation