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基本思想：OpenMP的变量私有化使用
（1）private子句将一个或多个变量变成私有化变量，每个线程都有独立的私有化同名变量副本，并不受外部同名变量的影响
它只可以用在迭代变量设置
#pragma omp parallel for private(i) for( i=0;i
或者
#pragma omp parallel private(i) { ..... } 测试代码
#include #include #include using namespace std;using namespace chrono;void sequentialProgram(int num){ int i=0; for( i=0;i (end_time-start_time).count()<<" seconds"< (end_time-start_time).count()<<" seconds"<
测试结果
F:\OpenMP\cmake-build-debug\OpenMP.exei=0 the current thread id: 0i=1 the current thread id: 0i=2 the current thread id: 0i=3 the current thread id: 0i=4 the current thread id: 0i=5 the current thread id: 0i=6 the current thread id: 0i=7 the current thread id: 0i=8 the current thread id: 0i=9 the current thread id: 0i=10 the current thread id: 0i=11 the current thread id: 0i=12sequentialProgram elapse time: 0.0345098 secondsi=1 the current thread id: 1i=2 the current thread id: 2i=3 the current thread id: 3i=4 the current thread id: 4i=5 the current thread id: 5i=7 the current thread id: 7i=6 the current thread id: 6i=10 the current thread id: 10i=0 the current thread id: 0i=8 the current thread id: 8i=11 the current thread id: 11i=9 the current thread id: 9i=110i=100 the current thread id: 1i=100 the current thread id: 3i=100 the current thread id: 2i=100 the current thread id: 7i=100 the current thread id: 6i=100 the current thread id: 5i=100 the current thread id: 4i=100 the current thread id: 9i=100 the current thread id: 8i=100 the current thread id: 10i=100 the current thread id: 0i=100 the current thread id: 11i=110parallelProgram elapse time: 0.058988 secondsProcess finished with exit code 0
（2）firstprivate 作用和private很类似 只能用于非迭代变量
int sum=0; int t=0;#pragma omp parallel for firstprivate(sum,t) for(int i=0;i
测试代码
#include #include #include using namespace std;using namespace chrono;void sequentialProgram(int num){ int sum=0; for(int i=0;i (end_time-start_time).count()<<" seconds"< (end_time-start_time).count()<<" seconds"<
测试结果
F:\OpenMP\cmake-build-debug\OpenMP.exesum=0 the current thread id: 0sum=1 the current thread id: 0sum=3 the current thread id: 0sum=6 the current thread id: 0sum=10 the current thread id: 0sum=15 the current thread id: 0sum=21 the current thread id: 0sum=28 the current thread id: 0sum=36 the current thread id: 0sum=45 the current thread id: 0sum=55 the current thread id: 0sum=66 the current thread id: 0sum=66sequentialProgram elapse time: 0.0289404 secondssum=2 t=-2 the current thread id: 2sum=6 t=-6 the current thread id: 6sum=3 t=-3 the current thread id: 3sum=4 t=-4 the current thread id: 4sum=5 t=-5 the current thread id: 5sum=1 t=-1 the current thread id: 1sum=8 t=-8 the current thread id: 8sum=10 t=-10 the current thread id: 10sum=7 t=-7 the current thread id: 7sum=9 t=-9 the current thread id: 9sum=0 t=0 the current thread id: 0sum=11 t=-11 the current thread id: 11sum=1111 t=0sum=1211 the current thread id: 2sum=1211 the current thread id: 6sum=1211 the current thread id: 4sum=1211 the current thread id: 5sum=1211 the current thread id: 1sum=1211 the current thread id: 10sum=1211 the current thread id: 7sum=1211 the current thread id: 9sum=1211 the current thread id: 8sum=1211 the current thread id: 0sum=1211 the current thread id: 11sum=1211 the current thread id: 3sum=1111parallelProgram elapse time: 0.0741342 secondsProcess finished with exit code 0
(3)lastprivate 只能用在for循环的私有变量中，最终结果会发生变化
#pragma omp parallel for lastprivate(i) for( i=0;i
测试代码
#include #include #include using namespace std;using namespace chrono;void sequentialProgram(int num){ int sum=0; for(int i=0;i (end_time-start_time).count()<<" seconds"< (end_time-start_time).count()<<" seconds"<
测试结果
F:\OpenMP\cmake-build-debug\OpenMP.exesum=0 the current thread id: 0sum=1 the current thread id: 0sum=3 the current thread id: 0sum=6 the current thread id: 0sum=10 the current thread id: 0sum=15 the current thread id: 0sum=21 the current thread id: 0sum=28 the current thread id: 0sum=36 the current thread id: 0sum=45 the current thread id: 0sum=55 the current thread id: 0sum=66 the current thread id: 0sum=66sequentialProgram elapse time: 0.028188 secondsi=1 sum=1 t=-1 the current thread id: 1i=3 sum=10 t=-10 the current thread id: 3i=4 sum=5 t=-5 the current thread id: 4i=2 sum=7 t=-7 the current thread id: 2i=5 sum=15 t=-15 the current thread id: 5i=6 sum=21 t=-21 the current thread id: 6i=7 sum=28 t=-28 the current thread id: 7i=8 sum=36 t=-36 the current thread id: 8i=10 sum=46 t=-46 the current thread id: 10i=9 sum=55 t=-55 the current thread id: 9i=0 sum=55 t=-55 the current thread id: 0i=11 sum=66 t=-66 the current thread id: 11i=12 sum=66 t=-66sum=166 the current thread id: 0sum=166parallelProgram elapse time: 0.0447262 secondsProcess finished with exit code 0
总结一下，
| 制导指令 | for | 非for | 多参数 | 参数类型 | 是否修改同名变量 | 初始值 | |
| private | 支持 | 支持 | 支持（不建议使用） | 迭代参数 | 否 | 使用同名变量值，省略初始值 | |
| firstprivate | 支持 | 支持 | 支持 | 不限 | 否 | 忽视掉同名变量值，使用初始值 | |
| lastprivate | 支持 | 不支持 | 不支持 | 迭代参数 | 是 | 忽视掉同名变量值，使用初始值 | |
三者可以结合使用~
#include #include #include using namespace std;using namespace chrono;void sequentialProgram(int num){ int sum=0; for(int i=0;i (end_time-start_time).count()<<" seconds"< (end_time-start_time).count()<<" seconds"<
测试结果
F:\OpenMP\cmake-build-debug\OpenMP.exesum=0 the current thread id: 0sum=1 the current thread id: 0sum=3 the current thread id: 0sum=6 the current thread id: 0sum=10 the current thread id: 0sum=15 the current thread id: 0sum=21 the current thread id: 0sum=28 the current thread id: 0sum=36 the current thread id: 0sum=45 the current thread id: 0sum=55 the current thread id: 0sum=66 the current thread id: 0sum=66sequentialProgram elapse time: 0.0221205 secondsi=1 sum=1 t=-1 the current thread id: 1i=3 sum=3 t=-4 the current thread id: 3i=5 sum=5 t=-9 the current thread id: 5i=0 sum=0 t=-9 the current thread id: 0i=4 sum=4 t=-21 the current thread id: 4i=8 sum=8 t=-17 the current thread id: 8i=2 sum=2 t=-29 the current thread id: 2i=6 sum=6 t=-27 the current thread id: 6i=10 sum=10 t=-39 the current thread id: 10i=11 sum=11 t=-50 the current thread id: 11i=9 sum=9 t=-59 the current thread id: 9i=7 sum=7 t=-66 the current thread id: 7i=10 sum=11 t=-66sum=111 the current thread id: 0sum=111parallelProgram elapse time: 0.0313515 secondsProcess finished with exit code 0
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