wiki:YMU110509/Lab2

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實作二

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實作二

多核心程式設計 : OpenMP
Multi-Cores Programming : OpenMP

GCC 4.2 以上版本就有支援 OpenMP 了....用 "gcc -fopenmp" 就可以編譯

Example 1 : HelloWorld

首先從 OpenMP Exercise 下載 omp_hello.c

~$ wget https://computing.llnl.gov/tutorials/openMP/samples/C/omp_hello.c

確認目前 gcc 版本，須大於 4.2 以後的版本

~$ gcc -v
Using built-in specs.
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian 4.4.5-8' --with-bugurl=file:///usr/share/doc/gcc-4.4/README.Bugs --enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-4.4 --enable-shared --enable-multiarch --enable-linker-build-id --with-system-zlib --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.4 --libdir=/usr/lib --enable-nls --enable-clocale=gnu --enable-libstdcxx-debug --enable-objc-gc --with-arch-32=i586 --with-tune=generic --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
gcc version 4.4.5 (Debian 4.4.5-8)

使用 GCC 編譯 omp_hello.c

~$ gcc -o omp_hello -fopenmp omp_hello.c

執行 omp_hello 執行檔

~$ ./omp_hello 
Hello World from thread = 2
Hello World from thread = 3
Hello World from thread = 0
Number of threads = 4
Hello World from thread = 1

首先從 OpenMP Exercise 下載 omp_workshare1.c

~$ wget https://computing.llnl.gov/tutorials/openMP/samples/C/omp_workshare1.c

使用 GCC 編譯 omp_workshare1.c

~$ gcc -o omp_workshare1 -fopenmp omp_workshare1.c

執行 omp_workshare1 執行檔

~$ ./omp_workshare1
~$ ./omp_workshare1
Thread 3 starting...
Thread 1 starting...
Number of threads = 4
Thread 0 starting...
Thread 0: c[20]= 40.000000
Thread 0: c[21]= 42.000000
Thread 0: c[22]= 44.000000
Thread 0: c[23]= 46.000000
Thread 0: c[24]= 48.000000
Thread 0: c[25]= 50.000000

 ... skipped ... 

Thread 2 starting...
Thread 2: c[90]= 180.000000
Thread 2: c[91]= 182.000000
Thread 2: c[92]= 184.000000
Thread 2: c[93]= 186.000000
Thread 2: c[94]= 188.000000

 ... skipped ... 

Thread 3: c[0]= 0.000000
Thread 3: c[1]= 2.000000
Thread 3: c[2]= 4.000000
Thread 3: c[3]= 6.000000
Thread 3: c[4]= 8.000000
Thread 3: c[5]= 10.000000
 
 ... skipped ... 

Thread 1: c[10]= 20.000000
Thread 1: c[11]= 22.000000
Thread 1: c[12]= 24.000000
Thread 1: c[13]= 26.000000
Thread 1: c[14]= 28.000000