When I link library during my code compilation (intel compiler), if I use
mpicc -lm -lmpi ..., I have a warning says:
icc: warning #10315: specifying -lm before files may supersede the Intel(R) math library and affect performance
Therefore I use intel's math library mkl, i.e. mpicc -mkl -lmpi .... I'm curious what's the difference between -mkl and -lm? If I just delete -lm without liking any math library, it also works. Why?
Related
It appears that with gcc, it is only possible to compile programs using Intel's Math Kernel Library in 32 bit mode, as per installation instructions
source /opt/intel/mkl/bin/mklvars.sh ia32
gcc -m32 example_program.c -lmkl_intel -lmkl_intel_thread -lmkl_core -liomp5 -lpthread -lm
If I try, for example
# Only options are ia32 or intel64
source /opt/intel/mkl/bin/mklvars.sh intel64
gcc example_program.c -lmkl_intel -lmkl_intel_thread -lmkl_core -liomp5 -lpthread -lm
I get the error:
/usr/bin/ld: cannot find -lmkl_intel
Is it impossible to compile programs using the Math Kernel Library in 64 bit without using icc, Intel's own C compiler?
Edit: additionally, when compiling I get the message
/usr/bin/ld: skipping incompatible /opt/intel/compilers_and_libraries_2018.2.199/linux/mkl/lib/ia32_lin/libmkl_intel.so when searching for -lmkl_intel
/usr/bin/ld: skipping incompatible /opt/intel/compilers_and_libraries_2018.2.199/linux/mkl/lib/ia32_lin/libmkl_intel.a when searching for -lmkl_intel
When compiling with:
gcc hertzian_analysis_nd.c -L"/opt/intel/compilers_and_libraries_2018.2.199/linux/mkl/lib/intel64_lin/libmkl_intel_ilp64.a" -lmkl_intel -lmkl_intel_thread -lmkl_core -liomp5 -lpthread -lm
I still get the same error.
I just cross-compiled the clang compiler for ARM on my x86 machine with instructions from here. I am trying to compile a c code containing NEON intrinsics with clang compiler. It is giving error, (which i do not encounter with arm-linux-gnueabi-gcc)
$ clang -march=armv7-a -mfpu=neon -mfloat-abi=soft -integrated-as test.c -o test
In file included from test.c:2:
/home/junaid/llvm/build/Release+Asserts/bin/../lib/clang/3.2/include/arm_neon.h:28:2: error:
"NEON support not enabled"
The line test.c:2 is #include arm_neon.h
It will be the -mfloat-abi=soft. I'm surprised that works for you with an arm-none-linux-gnueabi toolchain.
For Neon support you will want to be targetting either the softfp, or hard float ABI, with either -mfloat-abi=softfp or -mfloat-abi=hard
Is there any way to reduce the memory used by an executable generated with a command like gcc source_file.c -o result? I browsed the Internet and also looked in the man page for "gcc" and I think that I should use something related to -c or -S. So is gcc -c -S source_file.c -o result working? (This seems to reduce the space used...is there any other way to reduce even more?)
Thanks,
Polb
The standard compiler option on POSIX-like systems to instruct the compiler to optimize is -O (capital letter O for optimize). Many compilers allow you to optionally specify an optimization level after -O. Common optimization levels include:
-O0 no optimization at all
-O1 basic optimization for speed
-O2 all of -O1 plus some advanced optimizations
-O3 all of -O2 plus expensive optimizations that aren't usually needed
-Os optimize for size instead of speed (gcc, clang)
-Oz optimize even more for size (clang)
-Og all of -O2 except for optimizations that hinder debugging (gcc)
-Ofast all of -O3 and some numeric optimizations not in conformance with standard C. Use with caution. (gcc)
option -S generate assembler output.
Better option is using llvm and generating asembler for multi architecture. Similar http://kripken.github.io/llvm.js/demo.html
llc
here is example https://idea.popcount.org/2013-07-24-ir-is-better-than-assembly/
I am running mkl_lab_solution.c which is an example for using MKL, I can compile it correctly, while I run it, I got Segmentation fault.My runtime is below:
OS is centos 6.3
gcc's version is 4.1.2
mkl is mkl_10.3.12.361
makefile is below
gcc -g -L/opt/intel/composer_xe_2011_sp1.12.361/mkl/lib/intel64 -lmkl_intel_ilp64 -lmkl_intel_lp64 -lmkl_intel_sp2dp -lmkl_intel_thread -lmkl_core -lpthread -L/opt/intel/composer_xe_2011_sp1.12.361/compiler/lib/intel64 -liomp5 -L/usr/lib64 -lstdc++ -I/opt/intel/composer_xe_2011_sp1.12.361/mkl/include -o test mkl-lab-solution.c
Since this works fine on my system, let me point you to possible errors.
First, you need to run . /path/to/intel/compilervars.sh intel64 such all environment variables are set, like MKLROOT.
Second, check on intel mkl link line advisor for the options on your system. So reading your compile command I guess: linux, gnu compiler, dynamic linked, 64 bit target architecture, 64 bit long pointer, multithreaded, intel omp library.
These settings give me:
linker options:
-L$(MKLROOT)/lib/intel64 -lmkl_intel_ilp64 -lmkl_intel_thread -lmkl_core -liomp5 -lpthread -lm
compile options:
-DMKL_ILP64 -m64 -I$(MKLROOT)/include
For whatever reason the brackets around MKLROOT don't work on bash, so just remove them.
Next remember to put all compile options in front of linker options. The final command line should read like this:
gcc mkl-lab-solution.c -DMKL_ILP64 -m64 -I$MKLROOT/include -L$MKLROOT/lib/intel64 -lmkl_intel_ilp64 -lmkl_intel_thread -lmkl_core -liomp5 -lpthread -lm
Since you get runtime errors, I suspect that you are linking the Intel MKL libraries with objects compiled for different interface layers.
My program links to both PETSc and gsl, and both libraries were compiled with icc. Here's the link command:
/usr/local/mpich2/bin/mpicc -Wall -Wwrite-strings -Wno-strict-aliasing -Wno-unknown-pragmas -g3 -I/usr/local/gsl-icc-1.15/include/ -I/usr/local/gsl-icc-1.15/include/ -L/usr/local/gsl-icc-1.15/lib/ -lgsl -lgslcblas prog_name.o -L/usr/local/petsc-3.2-p6/lib -lpetsc -lX11 -lpthread -llapack -lblas -L/central/intel/Compiler-11.1.072/mkl/lib/em64t -L/central/intel/Compiler-11.1.072/lib/intel64 -L/central/intel/Compiler-11.1.072/tbb/intel64/cc3.4.3_libc2.3.4_kernel2.6.9/lib -L/usr/lib/gcc/x86_64-redhat-linux/4.1.2 -ldl -lgcc_s -lifport -lifcore -limf -lsvml -lm -lipgo -lirc -lpthread -lirc_s -lm -lstdc++ -lstdc++ -ldl -lgcc_s -ldl -o prog_name
MPICH_CC is set to icc, so mpicc calls the intel compiler.
When I try to link to the gsl .so file, I get the following errors:
gsl-icc-1.15/lib/libgsl.so: undefined reference to `__intel_sse2_strcpy'
gsl-icc-1.15/lib/libgsl.so: undefined reference to `__intel_sse2_strchr'
gsl-icc-1.15/lib/libgsl.so: undefined reference to `__intel_sse2_strncpy'
What could be the cause of this error? Is gsl incompatible with the intel compiler?
What could be the cause of this error?
You didn't show us your link command, but my crystall ball tells me that you are trying to link libgsl.so with ld (or perhaps with gcc), instead of icc.
In general, one should never link anything directly with ld on UNIX. Always use appropriate compiler driver (icc in this case).
I also get the same error message when linking some code with gcc against a PETSc version that was compiled with icc. Even more, when using the newest Intel 12.x compiler for the final code, and compiling PETSc with Intel 11.x results in the same error message as Intel 12.x uses 11.x.
So check, that mpicc really use the Intel 11.1.072 compiler. Check for mpic++ -show and which icc.
Maybe the intel environment not set.
Try the following environment setting:
source /etc/Intel_Compiler/10.0/XXXX/iccvars_intel64.sh
source /etc/Intel_Compiler/10.0/XXXX/ifortvars_intel64.sh
make the folder to your Intel Compiler folder. Some version's environment setting is different, you can also try:
source /etc/Intel_Compiler/10.0/XXXX/iccvars.sh intel64
source /etc/Intel_Compiler/10.0/XXXX/ifortvars.sh intel64
Hope helpfully.