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5164
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1 function amd_demo |
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2 % AMD DEMO |
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3 % |
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4 % A demo of AMD for OCTAVE. |
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5 % |
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6 % -------------------------------------------------------------------------- |
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7 % AMD Version 1.1 (Jan. 21, 2004), Copyright (c) 2004 by Timothy A. Davis, |
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8 % Patrick R. Amestoy, and Iain S. Duff. See ../README for License. |
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9 % email: davis@cise.ufl.edu CISE Department, Univ. of Florida. |
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10 % web: http://www.cise.ufl.edu/research/sparse/amd |
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11 % -------------------------------------------------------------------------- |
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12 % |
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13 % See also: amd |
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14 |
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15 % Get the Harwell/Boeing can_24 matrix. This is an example matrix from the |
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16 % MATLAB-accessible UF sparse matrix collection, and can be loaded into |
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17 % MATLAB with the statment "Problem = UFget ('HB/can_24')", after obtaining |
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18 % the UFget function and its supporting routines at |
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19 % http://www.cise.ufl.edu/sparse/mat . |
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20 |
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21 load can_24.mat |
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22 A = Problem.A ; |
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23 n = size (A,1) ; |
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24 |
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25 figure (1) |
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26 clf |
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27 hold off |
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28 subplot (2,1,1) ; |
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29 % remove the "_" from the name before printing it in the plot title |
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30 title (sprintf ('%s', strrep (Problem.name, '_', '-'))) ; |
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31 fprintf ('Matrix name: %s\n', Problem.name) ; |
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32 fprintf ('Matrix title: %s\n', Problem.title) ; |
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33 spy (A) |
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34 |
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35 % print the details during AMD ordering and SYMBFACT |
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36 control = amd (); |
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37 control (3) = 1; |
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38 |
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39 % order the matrix. Note that the Info argument is optional. |
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40 fprintf ('\nIf the next step fails, then you have\n') ; |
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41 fprintf ('not yet compiled the AMD mexFunction.\n') ; |
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42 [p, Info] = amd (A, control) ; |
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43 |
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44 % order again, but this time print some statistics |
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45 [p, Info] = amd (A, [10 1 1]) ; |
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46 |
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47 fprintf ('Permutation vector:\n') ; |
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48 fprintf (' %2d', p) ; |
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49 fprintf ('\n\n') ; |
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50 |
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51 subplot (2,1,2) ; |
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52 title ('Permuted matrix') ; |
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53 spy (A (p,p)) |
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54 |
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55 % approximations from amd: |
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56 lnz2 = n + Info (10) ; |
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57 fl2 = n + Info (11) + 2 * Info (12) ; |
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58 fprintf ('\nResults from AMD''s approximate analysis:\n') ; |
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59 fprintf ('number of nonzeros in L (including diagonal): %d\n', lnz2) ; |
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60 fprintf ('floating point operation count for chol (A (p,p)): %d\n\n', fl2) ; |
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61 |
