What's taking so long? - Profiling Open Babel

Profiling code shows where all the runtime is spent. In the case of Open Babel, profiling is a bit awkward due to its use of dynamically-loaded libraries (the format plugins, etc.). So here's how you do it on Linux...

[openbabel/build]$ rm CMakeCache.txt 
[openbabel/build]$ CXXFLAGS="-pg" LDFLAGS="-pg" cmake ../trunk -DCMAKE_INSTALL_PREFIX=../tree -DCMAKE_BUILD_TYPE=DEBUG -DBUILD_SHARED=OFF
[openbabel/build]$ make

This should successfully compile the library and plugins with profiling information, but will fail when it comes to linking one of the executables:

[openbabel/build]$ make obabel
[100%] Built target openbabel
Scanning dependencies of target obabel
[100%] Building CXX object tools/CMakeFiles/obabel.dir/obabel.o
Linking CXX executable ../bin/obabel
/usr/bin/ld: dynamic STT_GNU_IFUNC symbol `strcmp' with pointer equality in `/usr/lib/../lib64/libc.a(strcmp.o)' can not be used when making an executable; recompile with -fPIE and relink with -pie
collect2: error: ld returned 1 exit status
make[3]: *** [bin/obabel] Error 1
make[2]: *** [tools/CMakeFiles/obabel.dir/all] Error 2
make[1]: *** [tools/CMakeFiles/obabel.dir/rule] Error 2
make: *** [obabel] Error 2

Yikes! Using VERBOSE=1 we can see the offending command:

[openbabel/build]$ VERBOSE=1 make obabel 
cd /home/noel/Tools/openbabel/profile/build/tools && /usr/local/bin/cmake -E cmake_link_script CMakeFiles/obabel.dir/link.txt --verbose=1
/usr/local/bin/c++   -static -pg  -g -g3 -fno-inline   -pg CMakeFiles/obabel.dir/obabel.o  -o ../bin/obabel -rdynamic ../src/libopenbabel.a -Wl,-Bstatic -lpthread -Wl,-Bdynamic -lm -lz -Wl,-Bstatic 
/usr/bin/ld: dynamic STT_GNU_IFUNC symbol `strcmp' with pointer equality in `/usr/lib/../lib64/libc.a(strcmp.o)' can not be used when making an executable; recompile with -fPIE and relink with -pie
collect2: error: ld returned 1 exit status

With Roger's help, I was able to change this to something simpler which will compile:

[build/tools]$ /usr/local/bin/c++ -pg  -g -g3 -fno-inline   -pg CMakeFiles/obabel.dir/obabel.o  -o ../bin/obabel ../src/libopenbabel.a -lpthread -lm -lz

Success is mine AT LAST!! Now let's profile it:

[build/bin]$ export BABEL_DATADIR=wherever
[build/bin]$./obabel bigfile.smi -onul
[build/bin]$ gprof ./obabel > gprof.out

Now time to read the gprof manual.