What's the difference between ONLY_CBLAS or NO_FORTRAN in OpenBLAS build ?

[ayappanec]

I just want to understand the difference between setting ONLY_CBLAS=1 vs NO_FORTRAN=1 in OpenBLAS build ?

Let's say I don't have fortran compiler installed and I want to build OpenBLAS. If I try NO_FORTRAN=1, I see the build still passes -lgfortran and fails with cannot find -lgfortran: No such file or directory.
But with ONLY_CBLAS , the build went smoothly.,

[martin-frbg]

ONLY_CBLAS leaves out the entirety of LAPACK and the Fortran interfaces to the BLAS functions. NO_FORTRAN substitutes a f2c-translated (earlier) version of LAPACK so that one can still build everything except the Fortran-based tests. If you see that still passing -lgfortran anywhere and failing, it is an error in the build system (I'm guessing it is somewhere in the tests ?)

[ayappanec]

@martin-frbg Thanks for the explanation.
The first error encountered during the build with NO_FORTRAN=1 is while creating the main shared object.,

/opt/rh/gcc-toolset-13/root/usr/bin/gcc -O2 -DSMALL_MATRIX_OPT -DGEMM_GEMV_FORWARD -DSBGEMM_GEMV_FORWARD -DMAX_STACK_ALLOC=2048 -fopenmp -DHAVE_P10_SUPPORT -Wall -m64 -DF_INTERFACE_GFORT  -fPIC -DDYNAMIC_ARCH -DC_LAPACK -DSMP_SERVER -DUSE_OPENMP -DNO_WARMUP -DMAX_CPU_NUMBER=64 -DMAX_PARALLEL_NUMBER=1 -DBUILD_BFLOAT16 -DBUILD_SINGLE=1 -DBUILD_DOUBLE=1 -DBUILD_COMPLEX=1 -DBUILD_COMPLEX16=1 -DVERSION=\"0.3.30.dev\" -O3 -mcpu=power8 -mtune=power8 -mvsx  -fno-fast-math -DUSE_OPENMP -fopenmp -UASMNAME -UASMFNAME -UNAME -UCNAME -UCHAR_NAME -UCHAR_CNAME -DASMNAME= -DASMFNAME=_ -DNAME=_ -DCNAME= -DCHAR_NAME=\"_\" -DCHAR_CNAME=\"\" -DNO_AFFINITY -I..  -shared -o ../libopenblasp-r0.3.30.dev.so \
-Wl,--whole-archive ../libopenblasp-r0.3.30.dev.a -Wl,--no-whole-archive \
-Wl,-soname,libopenblas.so.0 -lm -lpthread -lgfortran -lm -lpthread
/opt/rh/gcc-toolset-13/root/usr/libexec/gcc/ppc64le-redhat-linux/13/ld: cannot find -lgfortran: No such file or directory
collect2: error: ld returned 1 exit status
make[1]: *** [Makefile:210: ../libopenblasp-r0.3.30.dev.so] Error 1
make[1]: Leaving directory '/home/buildusr/OpenBLAS/exports'
make: *** [Makefile:149: shared] Error 2

The next error happens during utest compilation.,

/opt/rh/gcc-toolset-13/root/usr/bin/gcc -O2 -DSMALL_MATRIX_OPT -DGEMM_GEMV_FORWARD -DSBGEMM_GEMV_FORWARD -DUTEST_CHECK -DSANITY_CHECK -DREFNAME=f_ -DMAX_STACK_ALLOC=2048 -fopenmp -DHAVE_P10_SUPPORT -Wall -m64 -DF_INTERFACE_GFORT  -fPIC -DDYNAMIC_ARCH -DC_LAPACK -DSMP_SERVER -DUSE_OPENMP -DNO_WARMUP -DMAX_CPU_NUMBER=64 -DMAX_PARALLEL_NUMBER=1 -DBUILD_BFLOAT16 -DBUILD_SINGLE=1 -DBUILD_DOUBLE=1 -DBUILD_COMPLEX=1 -DBUILD_COMPLEX16=1 -DVERSION=\"0.3.30.dev\" -O3 -mcpu=power8 -mtune=power8 -mvsx  -fno-fast-math -DUSE_OPENMP -fopenmp -UASMNAME -UASMFNAME -UNAME -UCNAME -UCHAR_NAME -UCHAR_CNAME -DASMNAME= -DASMFNAME=_ -DNAME=_ -DCNAME= -DCHAR_NAME=\"_\" -DCHAR_CNAME=\"\" -DNO_AFFINITY -I..  -o openblas_utest utest_main.o test_min.o test_amax.o test_ismin.o test_rotmg.o test_axpy.o test_dotu.o test_dsdot.o test_swap.o test_rot.o test_dnrm2.o test_zscal.o test_amin.o test_axpby.o test_gemv.o test_potrs.o test_kernel_regress.o test_post_fork.o ../libopenblasp-r0.3.30.dev.a -lm -lpthread -lgfortran -lm -lpthread -lm -lpthread
/opt/rh/gcc-toolset-13/root/usr/libexec/gcc/ppc64le-redhat-linux/13/ld: cannot find -lgfortran: No such file or directory
collect2: error: ld returned 1 exit status
make[1]: *** [Makefile:78: openblas_utest] Error 1
make[1]: Leaving directory '/home/buildusr/OpenBLAS/utest'
make: *** [Makefile:181: tests] Error 2

[martin-frbg]

There's probably a platform-specific extra -lgfortran as EXTRALIB without a "not NOFORTRAN" conditional in the makefiles - this does not occur on x86_64. I'll look later...

[martin-frbg]

I cannot reproduce this on POWER8 (ppc64le CentOS 7.9) with either the NO_FORTRAN or NOFORTRAN spelling variant.

[ayappanec]

I am using POWER8 (ppc64le RHEL 8.10) with the below build options.,
make CC=/opt/rh/gcc-toolset-13/root/usr/bin/gcc NO_FORTRAN=1 BINARY=64 USE_OPENMP=1 INTERFACE64=1 DYNAMIC_ARCH=1 USE_THREAD=1 TARGET=POWER8
After some debugging, it looks like -lgfortran is getting added via Makefile.system

#Don't include -lgfortran, when NO_LAPACK=1 or lsbcc
ifneq ($(NOFORTRAN), 1)
ifneq ($(NOFORTRAN), 2)
ifneq ($(NO_LAPACK), 1)
EXTRALIB += -lgfortran
endif
endif
endif

If I use NOFORTRAN=1 instead of NO_FORTRAN=1 , then the build succeeds.