R devel - Apr 2002 - understanding and resolving seg faults

Dear r-devel,

I am mutating rpart to do calculations on trees.
I am trying to extract information from the tree.

However, I got a seg. fault.


This is the offending line in "rpmatrix.c":  

            deltaI[0][0] = spl->improve;

(Commenting it out cures the seg fault)

I would like some advice on how to debug this.  I have allocated memory
with calloc and deltaI[0][0] should be OK, but apparently not.

thanks for your help,


For those that don't have structure of rpart drilled into their brain:

deltaI is declared in "rpmatrix.c":

void rpmatrix(struct node *me,  Sint *nodecount,   Sint *splitcount,
              Sint *catcount,   Sint *numcat,      double **dsplit,
              Sint **isplit,    Sint **csplit,     double **dnode,
              Sint **inode,     double **deltaI,      int id)
 
rpmatrix is called by "s_to_rp.c" where

ddeltaI is a pointer from an ALLOC call:
 
void s_to_rp2(Sint *n,         Sint *nsplit,    Sint *nnode,     Sint *ncat,
              Sint *numcat,    Sint *maxcat,    Sint *xvals,     Sint *which,
              double *cptable, double *dsplit,  Sint *isplit,    Sint *csplit,
              double *dnode,   double *deltaI,  Sint *inode)

    double   **ddeltaI; /* declaration of ddeltaI */

        ddeltaI = (double **) ALLOC(rp.num_y * rp.num_resp, sizeof(double ));
 
    rpmatrix(tree, nnode, nsplit, ncat, numcat,
                    ddsplit, iisplit, ccsplit, ddnode, iinode,ddeltaI ,1);

s_to_rp2 is called rpart.s


    rp    <- .C("s_to_rp2",
                       as.integer(nobs),
                       as.integer(nsplit),
                       as.integer(nodes),
                       as.integer(ncat),
                       as.integer(cats *!isord),
                       as.integer(max(cats)),
                       as.integer(xval),
                       which = integer(nobs),
                       cptable = matrix(double(numcp*cpcol), nrow=cpcol),
                       dsplit =  matrix(double(1),  nsplit,3),
                       isplit =  matrix(integer(1), nsplit,3),
                       csplit =  catmat,
                       dnode  =  matrix(double(1),  nodes, 3+numresp),
                       deltaI =  matrix(double(1),  nodes, nsplit),
                       inode  =  matrix(integer(1), nodes, 6))
 

 



-- 
Clayton Springer, Ph. D.
Sandia National Laboratories                      csprin@ca.sandia.gov
Biosystems Research Department                    (925) 294-2143
P.O. Box 969, MS 9951                fax:         (925) 294-3020
Livermore, CA, 94551-0969

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There is no such line in rpart's rpmatrix.c!

My guess is that you are misleading us, and that the segfault is in your
additions to rpart.  One of the issues covered by Open Source licences
is not misrepresenting code by not making clear that you have altered it.

Your debugger will tell you what is wrong with your C coding.  My guess
here is that as deltaI is a pointer to a pointer and you only mentioned
allocating deltaI, you failed to allocate deltaI[0].


On Wed, 24 Apr 2002, Clayton Springer wrote:
> Dear r-devel,
>
> I am mutating rpart to do calculations on trees.
> I am trying to extract information from the tree.
>
> However, I got a seg. fault.
>
>
> This is the offending line in "rpmatrix.c":
>
>             deltaI[0][0] = spl->improve;
>
> (Commenting it out cures the seg fault)
[...]

-- 
Brian D. Ripley,                  ripley@stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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r-devel mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
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