UMA and shared memory

UMA (Uniform Memory Access) is a memory architecture where all processors in a multiprocessor system have uniform access time to the shared memory. In UMA systems, there is no distinction between cores or processors regarding memory access latency. Each processor can access any memory location in the same amount of time.

When programming for UMA systems, you don’t need to explicitly create memory channels between cores because the memory is shared and accessible uniformly. You can simply access the shared memory from any core or processor without any additional steps.

Here’s an example program that demonstrates accessing shared memory in a UMA system:

#include <stdio.h>
#include <stdlib.h>
#include <omp.h>

#define ARRAY_SIZE 10

int main() {
    int sharedArray[ARRAY_SIZE];

    // Initialize the shared array
    for (int i = 0; i < ARRAY_SIZE; i++) {
        sharedArray[i] = i + 1;
    }

    // Parallel loop to modify the shared array
    #pragma omp parallel for
    for (int i = 0; i < ARRAY_SIZE; i++) {
        int threadID = omp_get_thread_num();
        sharedArray[i] += threadID;
    }

    // Print the modified shared array
    printf("Modified shared array:\n");
    for (int i = 0; i < ARRAY_SIZE; i++) {
        printf("%d ", sharedArray[i]);
    }
    printf("\n");

    return 0;
}

In this program, we have a shared array sharedArray that is accessible by all cores or threads in a UMA system. We use OpenMP directives to parallelize the loop and allow each thread to modify a portion of the shared array. The omp_get_thread_num() function is used to identify the current thread accessing the shared array.

Since UMA systems provide uniform memory access, there is no need to establish explicit memory channels between cores. All cores have equal access to the shared memory, and the modifications made by different threads are automatically visible to all other threads.

Note that this program assumes you have OpenMP support on your system, which is a common feature for parallel programming in C.