两个大数组相乘，有什么快速算法没有？感谢指导

#include <Windows.h>
#include <malloc.h>
typedef struct _MyParameter
{
    double *A, *B, *C;
    int start, length;
}MyParameter, *PMyParameter;

DWORD multiply_thread(PVOID pv)
{
    PMyParameter p = (PMyParameter)pv;
    for (int i = p->start; i < p->start + p->length; ++i)
    {
        p->C[i] = p->A[i] * p->B[i];
    }
    return 0;
}

void multiply(double *A, double *B, double *C, int length)
{
    SYSTEM_INFO system_info;
    GetSystemInfo(&system_info);
    //线程数为逻辑CPU数目2倍
    int numberOfThreads = system_info.dwNumberOfProcessors * 2;
    //线程句柄数组
    PHANDLE handles = (PHANDLE)malloc(sizeof(HANDLE) * numberOfThreads);
    if (handles == NULL)
    {
        return;
    }
    //参数数组
    PMyParameter parameters = (PMyParameter)malloc(sizeof(MyParameter) * numberOfThreads);
    if (parameters == NULL)
    {
        return;
    }
    //每线程计算长度
    int lengthPerThread = length / numberOfThreads;
    MyParameter parameter = { A,B,C,0,lengthPerThread };
    //多线程计算
    for (int i = 0; i < numberOfThreads; ++i)
    {
        parameters[i] = parameter;
        parameters[i].start = i * lengthPerThread;
        handles[i] = CreateThread(NULL, 0, multiply_thread, parameters + i, NULL, NULL);
    }
    for (int i = length / numberOfThreads * numberOfThreads; i < length; ++i)
    {
        C[i] = A[i] * B[i];
    }
    WaitForMultipleObjects(numberOfThreads, handles, TRUE, INFINITE);
    free(handles);
    free(parameters);
}