MPI_reduce a sum to an array element

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C++

parallelization

I have an problem in a parallelised code where I need to reduce values from all processors to the root process, summing them and then assigning the sum to an array element. I would like to do this in a loop such that each MPI_Reduce() call reduces to consecutive elements along an array. I would like to know how to point to the specific location in the array.

The part of the for-loop code is shown below:

for(int i = 1; i < N_t; i++) {
...............

            loc_EK = valEK * (cblas_ddot(loc_N, loc_vx, 1, loc_vx, 1) + 
            cblas_ddot(loc_N, loc_vy, 1, loc_vy, 1));
            loc_EP = valEP * cblas_dasum(loc_N, loc_y, 1);
            loc_ET = loc_EP + loc_EK;

            // Gather and sum loc_E components in root process
            MPI_Reduce(&loc_EK, (EK + 1 + i), 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD);
            MPI_Reduce(&loc_EP, (EP + 1 + i), 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD);
            MPI_Reduce(&loc_ET, (ET + 1 + i), 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD);
        }
    }

What I have tried:

I am currectly pointing the the array positions using (EK+i+1), where EK is the pointer to a dynamic array. I have tried using EK[i+1] but as expected this did not work. How should I fix this so that I can assign each reduced sum to elements of the array pointed to by EK?