58458 -> 1000 occurences
15 -> 412 occurences

#include <time.h>       // --- time
#include <stdlib.h>     // --- srand, rand
#include <iostream>

#include <thrusthost_vector.h>
#include <thrustdevice_vector.h>
#include <thrustsort.h>
#include <thrustiteratorzip_iterator.h>
#include <thrustunique.h>
#include <thrust/binary_search.h>
#include <thrustadjacent_difference.h>

#include "Utilities.cuh"
#include "TimingGPU.cuh"

//#define VERBOSE
#define NO_HISTOGRAM

/********/
/* MAIN */
/********/
int main() {

    const int N = 1048576;
    //const int N = 20;
    //const int N = 128;

    TimingGPU timerGPU;

    // --- Initialize random seed
    srand(time(NULL));

    thrust::host_vector<int> h_code(N);

    for (int k = 0; k < N; k++) {
        // --- Generate random numbers between 0 and 9
        h_code[k] = (rand() % 10);
    }

    thrust::device_vector<int> d_code(h_code);
    //thrust::device_vector<unsigned int> d_counting(N);

    thrust::sort(d_code.begin(), d_code.end());

    h_code = d_code;

    timerGPU.StartCounter();

#ifdef NO_HISTOGRAM
    // --- The number of d_cumsum bins is equal to the maximum value plus one
    int num_bins = d_code.back() + 1;

    thrust::device_vector<int> d_code_unique(num_bins);
    thrust::unique_copy(d_code.begin(), d_code.end(), d_code_unique.begin());
    thrust::device_vector<int> d_counting(num_bins);
    thrust::upper_bound(d_code.begin(), d_code.end(), d_code_unique.begin(), d_code_unique.end(), d_counting.begin());
#else
    thrust::device_vector<int> d_cumsum;

    // --- The number of d_cumsum bins is equal to the maximum value plus one
    int num_bins = d_code.back() + 1;

    // --- Resize d_cumsum storage
    d_cumsum.resize(num_bins);

    // --- Find the end of each bin of values - Cumulative d_cumsum
    thrust::counting_iterator<int> search_begin(0);
    thrust::upper_bound(d_code.begin(), d_code.end(), search_begin, search_begin + num_bins, d_cumsum.begin());

    // --- Compute the histogram by taking differences of the cumulative d_cumsum
    //thrust::device_vector<int> d_counting(num_bins);
    //thrust::adjacent_difference(d_cumsum.begin(), d_cumsum.end(), d_counting.begin());
#endif

    printf("Timing GPU = %fn", timerGPU.GetCounter());

#ifdef VERBOSE
    thrust::host_vector<int> h_counting(d_counting);
    printf("Aftern");
    for (int k = 0; k < N; k++) printf("code = %in", h_code[k]);
#ifndef NO_HISTOGRAM
    thrust::host_vector<int> h_cumsum(d_cumsum);
    printf("nCountingn");
    for (int k = 0; k < num_bins; k++) printf("element = %i; counting = %i; cumsum = %in", k, h_counting[k], h_cumsum[k]);
#else
    thrust::host_vector<int> h_code_unique(d_code_unique);

    printf("nCountingn");
    for (int k = 0; k < N; k++) printf("element = %i; counting = %in", h_code_unique[k], h_counting[k]);
#endif
#endif
}

First approach: 2.35ms
First approach without thrust::adjacent_difference: 1.52
Second approach: 4.67ms