Hi, Thanks Dirk for your suggestions. Let me try to clarify a few things below. Basically,
- zgels should not be needed (probably, and if I was doing things correctly) - I believe the template mechanism is simply unaware of the square format of my matrix, and defaults to the nrow < ncol case for lack of better knowledge. I do not know how to specify that the matrix is square, it's passed on from another function, i.e. https://github.com/baptiste/cda/blob/master/src/cd.cpp#L49 is using A from https://github.com/baptiste/cda/blob/master/src/cda.cpp#L129 The way I picture it, I need to give a hint of the square size, and armadillo will pick the right function/template/glue (I don't know the mechanism at play). On 1 June 2015 at 01:12, Dirk Eddelbuettel <e...@debian.org> wrote: > > Hi Baptiste, > > On 31 May 2015 at 20:47, Baptiste Auguie wrote: > | Dear list, > | > | My cda package (https://github.com/baptiste/cda) solves a linear system > Ax=b > | with Armadillo; win-builder and CRAN complain about a missing "zgels_" > when > | trying to build on windows or mac, as it's not part of the subset of > LAPACK > | provided by R libraries (I asked about this in 2011). I have included a > copy of > > Right. When no system lapack/blas is found, R uses its own. Which is a > subset. We were bitten that once and now check in configure for > availability > of zgesdd. I suppose this case is similar. > > Look at the logic in > > https://github.com/RcppCore/RcppArmadillo/blob/master/configure > > You may need to do something similar for zgels. So this part of the > problem > ("do we have zgels ?") really may be part of "which type of R installation > do > we have". > > Worst case we need new branching / #ifdef logic --- but right now I think > maybe more at the level of your package then at RcppArmadillo. > > The easiest workaround, I find, is to include zgels.f, as I've been doing since 2011. Now, my premise here is that this function is not needed in my package. > | this file (zgels.f) from Netlib for the past few years just to make the > problem > | go away, but I've recently realised that zgels is not supposed to be > called! It > | builds fine on Linux, or any machine with a full LAPACK installed, but > I'm now > | wondering if solve() always calls zgels (that would be inefficient for my > | use-case). > > From the top-level, when I just use ag (a fantastic and much faster grep > alternative; and mail will drop the ansi code for colour highlihting from > the > console) > Yes, I've tried to look at where zgels is called in the original Armadillo; it's not crystal clear (for me) with the templates and glue etc. > > edd@max:~/git/rcpparmadillo(master)$ ag zgels > inst/include/armadillo_bits/lapack_bones.hpp > 97: #define arma_zgels zgels > 205: #define arma_zgels ZGELS > 340: void arma_fortran(arma_zgels)(char* trans, blas_int* m, blas_int* n, > blas_int* nrhs, void* a, blas_int* lda, void* b, blas_int* ldb, void* > work, blas_int* lwork, blas_int* info); > > inst/include/armadillo_bits/lapack_wrapper.hpp > 689: arma_fortran(arma_zgels)(trans, m, n, nrhs, (T*)a, lda, (T*)b, > ldb, (T*)work, lwork, info); > edd@max:~/git/rcpparmadillo(master)$ > > I think you should discuss the merits of what gets called with Conrad. > Looking at the code and docs, the intent for square matrices is probably not to use zgels. I believe my code is simply failing to give enough hints for the templates to work out which case is actually being required. > > | The matrix A is square: the system is not under/overdetermined, and I > believe > | Armadillo should select LU factorisation rather than (slower) QR. Here's > the > > It is hard to answer this in full generality --- and even harder to change > an > existing API. > > If Armadillo has been using QR here for years, we cannot really change this > now on the request of a single package. > | error I get from win-builder when I remove zgels.f from my cda package, > | > | cd.o:cd.cpp: > | > (.text$_ZN4arma6auxlib8solve_udISt7complexIdENS_3MatIS3_EEEEbRNS4_IT_EES8_RKNS_4BaseIS6_T0_EE > | [bool arma::auxlib::solve_ud<std::complex<double>, arma::Mat<std::complex > | <double> > >(arma::Mat<std::complex<double> >&, > arma::Mat<std::complex<double> > | >&, arma::Base<std::complex<double>, arma::Mat<std::complex<double> > > > const > | &)]+0x3a5): undefined reference to `zgels_' > | > | So it thinks it should call solve_ud, which is meant for under-determined > | systems. Why would that be? > | I tried to find the relevant piece in the template code, this looks > relevant > | but I don't understand it: > https://github.com/RcppCore/RcppArmadillo/blob/ > | master/inst/include/armadillo_bits/glue_solve_meat.hpp#L26 > > Well that seems to be the call in the 'rows < cols' case. > I linked to the case which is returned in the win-builder log; the case of a square matrix would be a few lines earlier (note that the solve_ud case is the default, if previous conditions fail to apply). > > But if there is a function solve_ud, can you not just call solve_ud > from your package? > That would be auxlib::solve(out, A, X, slow); Yes, it's probably an option, although if I were to bypass the high-level solve() interface, I'd probably feel more comfortable with an explicit call to lu() instead. > > I haven't had coffee yet so I may not need the full picture. > Cheers, Dirk > Thanks! baptiste > > > > | > | Best regards, > | > | baptiste > | _______________________________________________ > | Rcpp-devel mailing list > | Rcpp-devel@lists.r-forge.r-project.org > | https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/rcpp-devel > > -- > http://dirk.eddelbuettel.com | @eddelbuettel | e...@debian.org >
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