Build with clang fails when NOFORTRAN=0

[shahrzad]

Hi,
I am trying to build OpenBlas with clang on Fedrora using:

make CC=clang USE_OPENMP=1

gfortran -O2 -Wall -m64 -fopenmp   -o cblat1 cblat1.o ../libopenblas_haswellp-r0.3.1.dev.a -lm -lpthread -lgfortran -lm -lpthread -lgfortran 
gfortran -O2 -Wall -m64 -fopenmp   -o zblat1 zblat1.o ../libopenblas_haswellp-r0.3.1.dev.a -lm -lpthread -lgfortran -lm -lpthread -lgfortran 
../libopenblas_haswellp-r0.3.1.dev.a(blas_server.o): In function `exec_blas':
blas_server_omp.c:(.text+0x26e): undefined reference to `__kmpc_fork_call'
../libopenblas_haswellp-r0.3.1.dev.a(blas_server.o): In function `.omp_outlined.':
blas_server_omp.c:(.text+0x307): undefined reference to `__kmpc_for_static_init_8'
blas_server_omp.c:(.text+0x599): undefined reference to `__kmpc_for_static_fini'
collect2: error: ld returned 1 exit status
make[1]: *** [Makefile:141: zblat1] Error 1
make[1]: *** Waiting for unfinished jobs....
../libopenblas_haswellp-r0.3.1.dev.a(blas_server.o): In function `exec_blas':
blas_server_omp.c:(.text+0x26e): undefined reference to `__kmpc_fork_call'
../libopenblas_haswellp-r0.3.1.dev.a(blas_server.o): In function `.omp_outlined.':
blas_server_omp.c:(.text+0x307): undefined reference to `__kmpc_for_static_init_8'
blas_server_omp.c:(.text+0x599): undefined reference to `__kmpc_for_static_fini'
collect2: error: ld returned 1 exit status
make[1]: *** [Makefile:138: cblat1] Error 1

and when I use NOFORTRAN=0:

make CC=clang USE_OPENMP=1 NOFORTRAN=0

clang -c -O2 -DMAX_STACK_ALLOC=2048 -fopenmp -Wall -m64 -DF_INTERFACE_GFORT -fPIC -DNO_AVX512 -DSMP_SERVER -DUSE_OPENMP -DNO_WARMUP -DMAX_CPU_NUMBER=32 -DMAX_PARALLEL_NUMBER=1 -DASMNAME=ztrtri_LU_parallel -DASMFNAME=ztrtri_LU_parallel_ -DNAME=ztrtri_LU_parallel_ -DCNAME=ztrtri_LU_parallel -DCHAR_NAME=\"ztrtri_LU_parallel_\" -DCHAR_CNAME=\"ztrtri_LU_parallel\" -DNO_AFFINITY -I../.. -DDOUBLE  -DCOMPLEX -DCOMPLEX -DDOUBLE -DUNIT trtri_L_parallel.c -o ztrtri_LU_parallel.o
clang -c -O2 -DMAX_STACK_ALLOC=2048 -fopenmp -Wall -m64 -DF_INTERFACE_GFORT -fPIC -DNO_AVX512 -DSMP_SERVER -DUSE_OPENMP -DNO_WARMUP -DMAX_CPU_NUMBER=32 -DMAX_PARALLEL_NUMBER=1 -DASMNAME=ztrtri_LN_parallel -DASMFNAME=ztrtri_LN_parallel_ -DNAME=ztrtri_LN_parallel_ -DCNAME=ztrtri_LN_parallel -DCHAR_NAME=\"ztrtri_LN_parallel_\" -DCHAR_CNAME=\"ztrtri_LN_parallel\" -DNO_AFFINITY -I../.. -DDOUBLE  -DCOMPLEX -DCOMPLEX -DDOUBLE -UUNIT trtri_L_parallel.c -o ztrtri_LN_parallel.o
ar  -ru ../../libopenblas_haswellp-r0.3.1.dev.a strtri_UU_single.o strtri_UN_single.o strtri_LU_single.o strtri_LN_single.o strtri_UU_parallel.o strtri_UN_parallel.o strtri_LU_parallel.o strtri_LN_parallel.o dtrtri_UU_single.o dtrtri_UN_single.o dtrtri_LU_single.o dtrtri_LN_single.o dtrtri_UU_parallel.o dtrtri_UN_parallel.o dtrtri_LU_parallel.o dtrtri_LN_parallel.o ctrtri_UU_single.o ctrtri_UN_single.o ctrtri_LU_single.o ctrtri_LN_single.o ctrtri_UU_parallel.o ctrtri_UN_parallel.o ctrtri_LU_parallel.o ctrtri_LN_parallel.o ztrtri_UU_single.o ztrtri_UN_single.o ztrtri_LU_single.o ztrtri_LN_single.o ztrtri_UU_parallel.o ztrtri_UN_parallel.o ztrtri_LU_parallel.o ztrtri_LN_parallel.o
make[2]: Leaving directory '/home/shahrzad/src/OpenBLAS_clang/OpenBLAS/lapack/trtri'
make[1]: Leaving directory '/home/shahrzad/src/OpenBLAS_clang/OpenBLAS/lapack'
make[1]: Entering directory '/home/shahrzad/src/OpenBLAS_clang/OpenBLAS/lapack-netlib'
Makefile:7: make.inc: No such file or directory
make[1]: *** No rule to make target 'make.inc'.  Stop.
make[1]: Leaving directory '/home/shahrzad/src/OpenBLAS_clang/OpenBLAS/lapack-netlib'
make: *** [Makefile:218: netlib] Error 2

for openmp, clang and gfortran I 'm using:

libomp-6.0.0-2.fc28.x86_64 : OpenMP runtime for clang
gcc-gfortran-8.0.1-0.20.fc28.x86_64 
clang-6.0.0-5.fc28.x86_64 : A C language family front-end for LLVM

Am I doing something wrong here?

[martin-frbg]

Not sure yet why it is failing to link against the clang openmp runtime (-lomp) in the first case. (I assume you did make clean before trying with different options ?)

Second case, make option handling in OpenBLAS is still a bit wonky as noted in #1422 - most of the time, the opposite of SOMEOPTION=1 is not SOMEOPTION=0 but just running without SOMEOPTION. (Some places only check if the option is defined or not, and not if it is set to one or zero...)

[shahrzad]

Thanks for your reply. Yes I do make clean before trying each option.
The thing is if I use make CC=clang USE_OPENMP=1 NOFORTRAN=1 everything works fine

OpenBLAS build complete. (BLAS CBLAS)

  OS               ... Linux             
  Architecture     ... x86_64               
  BINARY           ... 64bit                 
  C compiler       ... CLANG  (command line : clang)
  Library Name     ... libopenblas_haswellp-r0.3.1.dev.a (Multi threaded; Max num-threads is 32)

 Use OpenMP in the multithreading. Because of ignoring OPENBLAS_NUM_THREADS and GOTO_NUM_THREADS flags, 
 you should use OMP_NUM_THREADS environment variable to control the number of threads.

but if I don't specify it I get the error mentioned above.

[martin-frbg]

(1) seems the Makefiles in ctest and test both need to set CEXTRALIB=lomp in this case
(2) NOFORTRAN=0 is not yet handled correctly
#1629 should fix both these problems

[shahrzad]

Everything is built properly now using make CC=clang USE_OPENMP=1

OpenBLAS build complete. (BLAS CBLAS LAPACK LAPACKE)

  OS               ... Linux             
  Architecture     ... x86_64               
  BINARY           ... 64bit                 
  C compiler       ... CLANG  (command line : clang)
  Fortran compiler ... GFORTRAN  (command line : gfortran)
  Library Name     ... libopenblas_haswellp-r0.3.1.dev.a (Multi threaded; Max num-threads is 32)

 Use OpenMP in the multithreading. Because of ignoring OPENBLAS_NUM_THREADS and GOTO_NUM_THREADS flags, 
 you should use OMP_NUM_THREADS environment variable to control the number of threads.

Thank you so much for your fast reply and fix.