编译并运行示例

Created: November-22, 2018

在使用 GCC 4.4 版的 8 核 Linux 机器上，可以编译 C 代码并按以下方式运行：

$ gcc -std=c99 -O3 -fopenmp loop.c -o loopc -lm
$ OMP_NUM_THREADS=1 ./loopc
Computing 1000000 cosines and summing them with 1 threads took 0.095832s
$ OMP_NUM_THREADS=2 ./loopc
Computing 1000000 cosines and summing them with 2 threads took 0.047637s
$ OMP_NUM_THREADS=4 ./loopc
Computing 1000000 cosines and summing them with 4 threads took 0.024498s
$ OMP_NUM_THREADS=8 ./loopc
Computing 1000000 cosines and summing them with 8 threads took 0.011785s

对于 Fortran 版本，它给出：

$ gfortran -O3 -fopenmp loop.f90 -o loopf
$ OMP_NUM_THREADS=1 ./loopf
Computing 1000000 cosines and summing them with  1 threads took 0.0915s
$ OMP_NUM_THREADS=2 ./loopf
Computing 1000000 cosines and summing them with  2 threads took 0.0472s
$ OMP_NUM_THREADS=4 ./loopf
Computing 1000000 cosines and summing them with  4 threads took 0.0236s
$ OMP_NUM_THREADS=8 ./loopf
Computing 1000000 cosines and summing them with  8 threads took 0.0118s