54 lines
1.8 KiB
Mathematica
54 lines
1.8 KiB
Mathematica
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%%************************************************************
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%% Prod3: compute the entries of Q = A*B*C specified in
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%% nzlistQ.
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%%
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%% Q = Prod3(blk,A,B,C,sym,nzlistQ)
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%% Important: (a) A is assumed to be symmetric if nzlistQ
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%% has 2 columns (since mexProd2nz computes A'*B).
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%% (b) The 2nd column of nzlistQ must be sorted in
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%% ascending order.
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%%
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%% (optional) sym = 1, if Q is symmetric.
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%% = 0, otherwise.
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%% (optional) nzlistQ = list of non-zero elements of Q to be
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%% computed.
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%%*****************************************************************
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%% SDPT3: version 4.0
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%% Copyright (c) 1997 by
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%% Kim-Chuan Toh, Michael J. Todd, Reha H. Tutuncu
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%% Last Modified: 16 Sep 2004
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%%*****************************************************************
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function Q = Prod3(blk,A,B,C,sym,nzlistQ)
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if (nargin<5); sym = 0; end;
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checkcell = [iscell(A) iscell(B) iscell(C)];
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if (nargin==6)
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checkcell(1,4) = iscell(nzlistQ);
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else
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nzlistQ = inf;
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end
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%%
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if any(checkcell-1)
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if (size(blk,1) > 1)
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error('Prod3: blk and A,B,C are not compatible');
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end
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if strcmp(blk{1},'s')
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[len,len2] = size(nzlistQ);
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if (len == 0); nzlistQ = inf; len2 = 1; end;
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if (len2 == 1) & (nzlistQ == inf)
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tmp = Prod2(blk,A,B,0);
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Q = Prod2(blk,tmp,C,sym);
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else
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tmp = Prod2(blk,B,C,0);
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Q = mexProd2nz(blk,A,tmp,nzlistQ);
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if sym; Q = 0.5*(Q+Q'); end;
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end
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elseif strcmp(blk{1},'q') | strcmp(blk{1},'l') | strcmp(blk{1},'u')
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Q = A.*B.*C;
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end
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else
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error('Prod3: A,B,C,nzlistQ must all be matrices');
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end
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%%************************************************************
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