Concurrency/test/TestTBB.cc

0001 #include <iostream>
0002 #include <stdlib.h>
0003 #include "oneapi/tbb/global_control.h"
0004 #include "oneapi/tbb/parallel_for.h"
0005 #include "oneapi/tbb/blocked_range.h"
0006
0007 using namespace tbb;
0008 using namespace std;
0009
0010 class ArraySummer {
0011   int* p_array_a;
0012   int* p_array_b;
0013   int* p_array_sum;
0014
0015 public:
0016   // This empty constructor with an initialization list is used to setup calls to the function
0017   ArraySummer(int* p_a, int* p_b, int* p_sum) : p_array_a(p_a), p_array_b(p_b), p_array_sum(p_sum) {}
0018
0019   void operator()(const blocked_range<int>& r) const {
0020     for (int i = r.begin(); i != r.end(); i++) {  // iterates over the entire chunk
0021       p_array_sum[i] = p_array_a[i] + p_array_b[i];
0022     }
0023   }
0024 };
0025
0026 int main(int argc, char* argv[]) {
0027   int* p_A;
0028   int* p_B;
0029   int* p_SUM_1T;
0030   int* p_SUM_TBB;
0031
0032   /* This is the TBB runtime... */
0033   global_control control(global_control::max_allowed_parallelism, 4);
0034
0035   constexpr int nElements = 10;
0036
0037   p_A = new int[nElements];
0038   p_B = new int[nElements];
0039   p_SUM_1T = new int[nElements];
0040   p_SUM_TBB = new int[nElements];
0041
0042   /*
0043   * Initialize the data sets ... could do this in parallel too, but
0044   * serial is easier to read
0045   */
0046   p_A[0] = p_B[0] = 0;
0047   p_A[1] = p_B[1] = 1;
0048   for (int i = 2; i < nElements; i++) {
0049     p_A[i] = (p_A[i - 1] + p_A[i - 2]) % (INT_MAX / 2);
0050     p_B[i] = p_A[i];
0051     p_SUM_1T[i] = 0;
0052     p_SUM_TBB[i] = 0;
0053   }
0054
0055   /*
0056   * Time how long it takes to sum the arrays using a single thread
0057   */
0058   for (int i = 0; i < nElements; i++) {
0059     p_SUM_1T[i] = p_A[i] + p_B[i];
0060   }
0061
0062   /*
0063   * Now sum the arrays again using TBB, again timing the execution
0064   */
0065
0066   parallel_for(blocked_range<int>(0, nElements, 100), ArraySummer(p_A, p_B, p_SUM_TBB));
0067
0068   /*
0069   * Verify the sums match
0070   */
0071   for (int i = 0; i < nElements; i++) {
0072     if (p_SUM_1T[i] != p_SUM_TBB[i]) {
0073       cout << p_A[i] << " + " << p_B[i] << " = " << p_SUM_1T[i] << " AND " << p_SUM_TBB[i] << endl;
0074     }
0075   }
0076
0077   delete[] p_A;
0078   delete[] p_B;
0079   delete[] p_SUM_1T;
0080   delete[] p_SUM_TBB;
0081
0082   return 0;
0083 }