env set as follow when you build gromacs
cmake .. -DGMX_BUILD_OWN_FFTW=OFF -DREGRESSIONTEST_DOWNLOAD=OFF -DCMAKE_INSTALL_PREFIX=/public/home/fenglk/Program/gromacs512/ -DGMX_SIMD=AVX_256 -DREGRESSIONTEST_PATH=/public/home/fenglk/Program/gromacs512/regressiontests-5.1.2/ -DCMAKE_PREFIX_PATH=/public/home/fenglk/Program/fftw333/
me
cmake .. -DGMX_BUILD_OWN_FFTW=OFF -DREGRESSIONTEST_DOWNLOAD=OFF -DCMAKE_INSTALL_PREFIX=/public/home/yaop/software/gromacs-5.1.3/ -DGMX_SIMD=AVX_256 -DREGRESSIONTEST_PATH=/public/home/yaop/software/gromacs-5.1.3/regressiontests-5.0.7/ -DCMAKE_PREFIX_PATH=/public/software/mathlib/fftw/3.3.3/double/lib