From marcin at galton.uchicago.edu  Fri Sep  4 07:58:54 2009
From: marcin at galton.uchicago.edu (Marcin Hitczenko)
Date: Fri, 4 Sep 2009 00:58:54 -0500 (CDT)
Subject: [Rd] calling Lapack and BLAS routines from C
Message-ID: <51649.207.181.247.22.1252043934.squirrel@galton.uchicago.edu>

Hi,

I am working on a UNIX machine and I am interfacing R and C with the .C
function. I am trying to call LAPACK and BLAS routines, but am running
into a problem where, while I am able to run the BLAS routines, I cannot
run the LAPACK routines.

I compile my .c file (at end of email) in the following way:

[mhitczen at jlogin2 ~/Cstuff]$ R CMD SHLIB testmore.c

gcc -std=gnu99 -I/home/mhitczen/R-2.9.0/include  -I/usr/local/include   
-fpic  -g -O2 -c testmore.c -o testmore.o
gcc -std=gnu99 -shared -L/usr/local/lib -o testmore.so testmore.o

However, I get the following error in R:

> dyn.load("testmore.so")
Error in dyn.load("testmore.so") :
  unable to load shared library '/home/mhitczen/Cstuff/testmore.so':
/home/mhitczen/Cstuff/testmore.so: undefined symbol: dpotrf_

This error goes away and everything works when I simply call the BLAS
routine (In the testmore.c file I simply remove funct2, leaving funct
which calls the routine "dgemm" found in the BLAS.h file).

I read the "Writing R Extensions" and created a file:
/R-2.9.0/src/Makevars that contains the line:
PKG_LIBS = $(LAPACK_LIBS) $(BLAS_LIBS) $(FLIBS)

What am I doing wrong? Thanks for your time and effort.

My testmore.c file is:

#include <Rinternals.h>
#include <Rmath.h>
#include <R.h>
#include <R_ext/Applic.h>
#include <R_ext/Lapack.h>
#include <R_ext/BLAS.h>
#include <R_ext/RS.h>

// FUNCTION CALLING BLAS
void funct(double *x, int *dim, double *y, double *result){

  double one=1.0; double zero =0.0;
  char *transa="N"; char *transb="N";

  F77_CALL(dgemm)
(transa,transb,dim,dim,dim,&one,x,dim,y,dim,&zero,result,dim);
}

// FUNCTION CALLING LAPACK
void funct4(double *x, int *dim, double *result){

  char *UorL="L";
  int info=0;

  F77_CALL(dpotrf)(UorL,dim,x,dim, &info);
}



Best,

Marcin Hitczenko



[Rd] calling Lapack and BLAS routines from C
Marcin Hitczenko