Mercurial > matrix-functions
comparison funm_files/swapping.m @ 0:8f23314345f4 draft
Create local repository for matrix toolboxes. Step #0 done.
| author | Antonio Pino Robles <data.script93@gmail.com> |
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| date | Wed, 06 May 2015 14:56:53 +0200 |
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| -1:000000000000 | 0:8f23314345f4 |
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| 1 function [M,ind,n_swaps] = swapping(m) | |
| 2 %SWAPPING Confluent permutation by swapping adjacent elements. | |
| 3 % [ISWAP,IND,N_SWAPS] = SWAPPING(M) takes a vector M containing | |
| 4 % the integers 1:k (some repeated if K < LENGTH(M)) | |
| 5 % and constructs a swapping scheme that produces | |
| 6 % a confluent permutation, with elements ordered by ascending | |
| 7 % average position. The confluent permutation is obtained by using | |
| 8 % the LAPACK routine ZTREX to move m(ISWAP(i,2)) to m(ISWAP(i,1)) | |
| 9 % by swapping adjacent elements, for i = 1:SIZE(M,1). | |
| 10 % The cell array vector IND defines the resulting block form: | |
| 11 % IND{i} contains the indices of the i'th block in the permuted form. | |
| 12 % N_SWAPS is the total number of swaps required. | |
| 13 | |
| 14 mmax = max(m); M = []; ind = {}; h = zeros(1,mmax); | |
| 15 g = zeros(1,mmax); | |
| 16 | |
| 17 for i = 1:mmax | |
| 18 p = find(m==i); | |
| 19 h(i) = length(p); | |
| 20 g(i) = sum(p)/h(i); | |
| 21 end | |
| 22 | |
| 23 [x,y] = sort(g); | |
| 24 mdone = 1; | |
| 25 | |
| 26 for i = y | |
| 27 if any(m(mdone:mdone+h(i)-1) ~= i) | |
| 28 f = find(m==i); g = mdone:mdone+h(i)-1; | |
| 29 ff = f(f~=g); gg = g(f~=g); | |
| 30 | |
| 31 % Create vector v = mdone:f(end) with all elements of f deleted. | |
| 32 v = mdone-1 + find(m(mdone:f(end)) ~= i); | |
| 33 | |
| 34 % v = zeros(1,f(end)-g(1)+1); | |
| 35 % v(f-g(1)+1) = 1; v = g(1)-1 + find(v==0); | |
| 36 | |
| 37 M(end+1:end+length(gg),:) = [gg' ff']; | |
| 38 | |
| 39 m(g(end)+1:f(end)) = m(v); | |
| 40 m(g) = i*ones(1,h(i)); | |
| 41 ind = cat(2,ind,{mdone:mdone+h(i)-1}); mdone = mdone + h(i); | |
| 42 else | |
| 43 ind = cat(2,ind,{mdone:mdone+h(i)-1}); mdone = mdone + h(i); | |
| 44 end | |
| 45 end | |
| 46 | |
| 47 n_swaps = sum(abs(diff(M'))); |