On Mon, Dec 17, 2012 at 8:02 AM, William Dunlap <wdun...@tibco.com> wrote:
> The problem almost certainly lies in the parts of the code that you have
> not shown, the R-language code including the .Call or, more likely in my
> opinion, the C++ code for Projector.
I would have blamed the unPROTECTed coerceVector() result in the getDim
macro.
-thomas
> You can get different values in
> Projector's Lsum matrix if
> (a) Projector doesn't assign values to all of them (allocMatrix
> allocates memory
> with random contents - you must fill it with values)
> (b) Projector reads or writes memory that it doesn't own.
> Using valgrind can help find both sorts of errors.
>
> I am suspicious about your reversal of the dimensions of Lsum when
> you allocate it, using dimG[1],dimG[0]. Does this mean you are doing
> some odd pointer arithmetic in Projector that doesn't agree with R's
> conventions?
>
> I tried adding a simple Projector() and saw no problems aside from
> the random numbers in the unassigned elements of Lsum and some
> of the usual unassign values in the guts of Rprintf's formatting code.
>
> extern "C" {
> SEXP Projector5(SEXP L, SEXP G, SEXP W, SEXP xymod, SEXP modif);
> }
>
> //* the Projector part *//
> void Projector(double *L, int *dimL, double *G, int *dimG, double *W, int
> *dimW,
> int *xymod, int *dimxy, double *modif, int *dimif, double *Lsum)
> {
> Rprintf("dimG=c(%d,%d)\n", dimG[0], dimG[1]);
> double* pLsum = Lsum;
> bool even = true ;
> for(int j=0 ; j < dimG[0] ; j++) {
> for(int i=0 ; i < dimG[1] ; i++) {
> if (even) {
> *pLsum = 1000 * (i+1) + (j+1);
> } else {
> // do not touch odd elements of pLsum
> }
> even = !even;
> pLsum++;
> }
> }
> }
>
> called with
> > .Call("Projector5", matrix(1:6,2,3), matrix(701:720,4,5),
> matrix(2^(1:12),2,6), 1:7, 1:10)
> dimG=c(4,5)
> [,1] [,2] [,3] [,4]
> [1,] 1001 7.954e-322 1003 4.002e-322
> [2,] 0 2.002e+03 0 2.004e+03
> [3,] 3001 0.000e+00 3003 0.000e+00
> [4,] 0 4.002e+03 0 4.004e+03
> [5,] 5001 0.000e+00 5003 0.000e+00
>
> Bill Dunlap
> Spotfire, TIBCO Software
> wdunlap tibco.com
>
>
> > -----Original Message-----
> > From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org]
> On Behalf
> > Of Shangru Li
> > Sent: Sunday, December 16, 2012 10:20 AM
> > To: r-help@r-project.org
> > Subject: [R] interfacing with .Call
> >
> > Hi
> >
> > My code is as following:
> >
> > #include <R.h>
> > #include <Rinternals.h>
> >
> > //* the Projector part *//
> > void Projector(double *L, int *dimL, double *G, int *dimG, double *W, int
> > *dimW, int *xymod, int *dimxy, double *modif, int *dimif, double *Lsum)
> > { ...}
> >
> > //* the interface part *//
> > #define getDim(A) INTEGER(coerceVector(getAttrib(A,R_DimSymbol), INTSXP))
> >
> > SEXP Projector5(SEXP L, SEXP G, SEXP W, SEXP xymod, SEXP modif)
> > {
> > //* digest SEXPs from R *//
> > int *dimL, *dimG, *dimW, *dimxy, *dimif;
> > double *lptr, *gptr, *wptr, *ifptr;
> > int *xyptr;
> > dimL=getDim(L);
> > PROTECT(L=coerceVector(L, REALSXP));
> > lptr=REAL(L);
> > dimG=getDim(G);
> > PROTECT(G=coerceVector(G, REALSXP));
> > gptr=REAL(G);
> > dimW=getDim(W);
> > PROTECT(W=coerceVector(W, REALSXP));
> > wptr=REAL(W);
> > dimxy=getDim(xymod);
> > PROTECT(xymod=coerceVector(xymod, INTSXP));
> > xyptr=INTEGER(xymod);
> > dimif=getDim(modif);
> > PROTECT(modif=coerceVector(modif, REALSXP));
> > ifptr=REAL(modif);
> >
> > //* create SEXP to hold the answer *//
> > SEXP ans;
> > double *ansptr;
> > PROTECT(ans=allocMatrix(REALSXP, dimG[1], dimG[0]));
> > ansptr=REAL(ans);
> >
> > //* calculate the result *//
> > Projector(lptr, dimL, gptr, dimG, wptr, dimW, xyptr, dimxy, ifptr,
> > dimif, ansptr);
> >
> > //* wrap up and return the result to R *//
> > UNPROTECT(6);
> > return(ans);
> > }
> >
> > The function "Projector" works well and actually the interface with .C
> > works OK.
> > The question is that I can compile it in R, but ".Call" returns different
> > result each time with same inputs. Could anybody tell me why? Thanks!
> >
> > Regards
> > Shangru
> >
> > --
> > Department of Mathematics,
> > National University of Singapore,
> > Blk S17, 10 Lower Kent Ridge Road,
> > 119076
> >
> >
> >
> >
> >
> > --
> > Department of Mathematics,
> > National University of Singapore,
> > Blk S17, 10 Lower Kent Ridge Road,
> > 119076
> >
> > [[alternative HTML version deleted]]
> >
> > ______________________________________________
> > R-help@r-project.org mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
--
Thomas Lumley
Professor of Biostatistics
University of Auckland
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