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*From*: Alexis Tantet <alexis dot tantet at gmail dot com>*To*: Patrick Alken <alken at colorado dot edu>*Cc*: "gsl-discuss at sourceware dot org" <gsl-discuss at sourceware dot org>*Date*: Sun, 7 Feb 2016 21:31:45 +0100*Subject*: Re: Sparse matrix extension*Authentication-results*: sourceware.org; auth=none*References*: <CAMWWPT3uJj4Vrn7ut6+F18gY===zd6+1r1UJhz0hcCj--zwtdg at mail dot gmail dot com> <CAMWWPT3Y=x-vYphaV+2gHPb9WZqEfYdDxs4T0KqBq987VjvDQA at mail dot gmail dot com> <569E6C33 dot 1090505 at colorado dot edu> <CAMWWPT2kMe=R0qUz4P6n_xzG+oW-8pOFwCtBuaritZ5MF6jzAg at mail dot gmail dot com> <569EA1A9 dot 2080101 at colorado dot edu> <CAMWWPT2d=PnK1cexcZ+OLQAYJudRk9QLGac-Wcn33OaES5UjJA at mail dot gmail dot com> <56B689B1 dot 5090005 at colorado dot edu> <CAMWWPT1mog0HrviL1tMo=f-rrSc2PhamWDGg7ZYLrVnnqkY3ng at mail dot gmail dot com> <56B77E13 dot 1000306 at colorado dot edu> <CAMWWPT2KTLjufNdwW=y-xaJ1dKkxDNQwgat4DB4ZwKDrK_fZSA at mail dot gmail dot com> <56B7A59D dot 5040707 at colorado dot edu>

I'm not sure I got your last point. I have the following situation in mind: Start to construct a transition matrix in triplet format, adding one element after another. In this particular example, each element is one count of a transition from (state, box, etc.) i to j, so I add elements (i, j, 1) to the triplet object, with possibly duplicates. What happen to these duplicates in the binary tree? Eventually, when I compress to CRS or CCS, I would like the duplicates to be summed up, so that element (i, j) counts transitions from i to j (and no duplicates exist after compression). Is this more clear? On Sun, Feb 7, 2016 at 9:14 PM, Patrick Alken <alken@colorado.edu> wrote: > Hi Alexis, > >>> I'm not sure what you mean. I've added a new function gsl_spmatrix_ptr >>> to the git, which as far as I can tell does exactly what your >>> sum_duplicate flag does. It searches the matrix for an (i,j) element, >>> and if found returns a pointer. If not found a null pointer is returned. >>> This makes it easy for the user to modify A(i,j) after it has been added >>> to the matrix. Are you thinking of something else? Can you point me to >>> the Eigen routine? >>> >> What I meant is to have the equivalent of gsl_spmatrix_compress, >> with the difference that gsl_spmatrix_ptr is used instead of gsl_spmatrix_set, >> so has to build the compressed matrix from triplets, summing the >> duplicates, instead of replacing them. >> This is what is done here : >> The http://eigen.tuxfamily.org/dox/classEigen_1_1SparseMatrix.html#a5bcf3187e372ff7cea1e8f61152ae49b >> >> Best, >> Alexis > > I'm not sure why a user would ever need to do this. The whole point of > the binary tree structure in the triplet storage is to efficiently find > duplicate entries, so that if a user tries to call gsl_spmatrix_set on > an element which is already been previously set, it can find that > element with a binary search (rather than linearly searching the arrays) > and change the value of that element. > > Therefore, the way the triplet storage is designed, there is will never > be a duplicate element in the triplet arrays. All of the (i[n],j[n]) > will be unique for each n <= nz. > > Am I missing something? > > Patrick -- Alexis Tantet

**Follow-Ups**:**Re: Sparse matrix extension***From:*Patrick Alken

**References**:**Re: Sparse matrix extension***From:*Alexis Tantet

**Re: Sparse matrix extension***From:*Patrick Alken

**Re: Sparse matrix extension***From:*Alexis Tantet

**Re: Sparse matrix extension***From:*Patrick Alken

**Re: Sparse matrix extension***From:*Alexis Tantet

**Re: Sparse matrix extension***From:*Patrick Alken

**Re: Sparse matrix extension***From:*Alexis Tantet

**Re: Sparse matrix extension***From:*Patrick Alken

**Re: Sparse matrix extension***From:*Alexis Tantet

**Re: Sparse matrix extension***From:*Patrick Alken

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