Question

我正在编写一个并行程序，它使用多个pthread来操作方形矩阵中的值，直到达到指定点。我正在使用pthread屏障来指示线程启动并让main（）知道何时更新矩阵。

基本上，我有两个矩阵：

readMatrix：包含writeMatrix要使用的当前迭代值。
writeMatrix：由线程使用readMatrix值运行的计算更新。

迭代完成后，交换读写矩阵。然后循环使用更新的读取矩阵继续。

然而，有一个问题;在迭代中，不存储已交换的读取矩阵值。

我使用struct将所有指针变量传递给启动的线程：

struct matrixStruct {
    double** readMatrix;
    double** writeMatrix;
    int dimension;
    int totalThreads;
    int threadNumber;
    int lowerBound;
    int upperBound;
};

这里是在main（）中启动线程的位置，然后是控制线程的工作循环，交换矩阵并检查它是否已达到目标：

pthread_t threads[totalThreads];
int rc;
long t;
for( t = 0; t < totalThreads; t++)
{
    structInstance[t].readMatrix = readMatrix;
    structInstance[t].writeMatrix = writeMatrix;
    structInstance[t].dimension = dimension;
    structInstance[t].totalThreads = totalThreads;
    structInstance[t].threadNumber = t;
    structInstance[t].lowerBound = t*innerCellAmountByThread;
    structInstance[t].upperBound = findUpperBound(t, innerCellAmountByThread, totalThreads, remainderOfCells);
    rc = pthread_create(&threads[t], NULL, initiateThread, &structInstance[t]);
    if (rc)
    {
        printf("ERROR; return code from pthread_create() is %d\n", rc);
        exit(-1);
    }
}

int precisionCheck = 0;
// Working while loop
while(precisionCheck != 1) {
    // Start all threads
    pthread_barrier_wait(&barrier1);

    // Wait for them to finish
    pthread_barrier_wait(&barrier2);

    // Swap matrix and then check for precision
    double** tempMatrix;
    tempMatrix = writeMatrix;
    writeMatrix = readMatrix;
    readMatrix = tempMatrix;

    precisionCheck = verifyPrecision(readMatrix, writeMatrix, precision, dimension);
}

以下是每个主题的作用：

void *initiateThread(void *structArg) {
    struct matrixStruct *structInstance = structArg;
    double** readMatrix = structInstance->readMatrix;
    double** writeMatrix = structInstance->writeMatrix;
    int dimension = structInstance->dimension;
    int totalThreads = structInstance->totalThreads;
    int threadNumber = structInstance->threadNumber;
    int lowerBound = structInstance->lowerBound;
    int upperBound = structInstance->upperBound;

    printf("threadNumber: %d lower: %d upper: %d\n\n", threadNumber, lowerBound, upperBound);

    while(endFlag == 0) {
        pthread_barrier_wait(&barrier1);

        relaxMatrixWithBounds(readMatrix, writeMatrix, dimension, lowerBound, upperBound);

        pthread_barrier_wait(&barrier2);
    }

    pthread_exit(NULL);
}

总而言之，我需要readMatrix来实际将更新的值存储在迭代中。

非常感谢任何帮助。

干杯

C线程迭代时C变量未更新

0 个答案: