Normally, I do the following to configure R for compilation on my Opteron box with ACML installed: ./configure --with-tcltk --with-blas="-L/opt/acml4.3.0/gfortran64/lib -lacml" However, when I do so, and look at Makeconf, I see BLAS_LIBS = -lblas I thought I would see BLAS_LIBS = -L/opt/acml4.3.0/gfortran64/lib -lacml Why isn't Makeconf picking up the right BLAS_LIBS (or is it? does -lblas mean its finding the right blas?). I tried LD_LIBRARY_PATH=/opt/acml4.3.0/gfortran64/lib export LD_LIBRARY_PATH and then did a new Configure, but Makeconf still shows only BLAS_LIBS = -lblas When I look at config.log, I see a 'failure' that I think might be part of the story: configure:37157: result: no configure:37199: checking for dgemm_ in -L/opt/acml4.3.0/gfortran64/lib -lacml configure:37230: gcc -std=gnu99 -o conftest -g -O2 -I/usr/local/include -L/usr/local/lib64 conftest.c -L/opt/acml4.3.0/gfo$ conftest.c: In function 'main': conftest.c:189: warning: implicit declaration of function 'dgemm_' /usr/bin/ld: warning: libgfortran.so.3, needed by /opt/acml4.3.0/gfortran64/lib/libacml.so, not found (try using -rpath or -$ /opt/acml4.3.0/gfortran64/lib/libacml.so: undefined reference to `_gfortran_compare_string at GFORTRAN_1.0' /opt/acml4.3.0/gfortran64/lib/libacml.so: undefined reference to `_gfortran_transfer_character at GFORTRAN_1.0' /opt/acml4.3.0/gfortran64/lib/libacml.so: undefined reference to `_gfortran_transfer_integer at GFORTRAN_1.0' /opt/acml4.3.0/gfortran64/lib/libacml.so: undefined reference to `_gfortran_stop_numeric at GFORTRAN_1.0' /opt/acml4.3.0/gfortran64/lib/libacml.so: undefined reference to `_gfortran_st_write_done at GFORTRAN_1.0' /opt/acml4.3.0/gfortran64/lib/libacml.so: undefined reference to `_gfortran_pow_i4_i4 at GFORTRAN_1.0' /opt/acml4.3.0/gfortran64/lib/libacml.so: undefined reference to `_gfortran_transfer_real at GFORTRAN_1.0' /opt/acml4.3.0/gfortran64/lib/libacml.so: undefined reference to `_gfortran_st_read at GFORTRAN_1.0' /opt/acml4.3.0/gfortran64/lib/libacml.so: undefined reference to `_gfortran_st_read_done at GFORTRAN_1.0' /opt/acml4.3.0/gfortran64/lib/libacml.so: undefined reference to `_gfortran_st_write at GFORTRAN_1.0' /opt/acml4.3.0/gfortran64/lib/libacml.so: undefined reference to `_gfortran_concat_string at GFORTRAN_1.0' /opt/acml4.3.0/gfortran64/lib/libacml.so: undefined reference to `_gfortran_string_index at GFORTRAN_1.0' collect2: ld returned 1 exit status configure:37236: $? = 1 configure: failed So, perhaps things go awry at this point...weird thing is, thee is no libgfortran.so.3 anywhere on the system that I can find....