Sample solution

Content

Controlling concurrent access to a shared resource
Sample solution
Pool pattern
Sample solution
Avoiding the overhead of copying
Sample solution
Condition variables
Sample solution

#include <cstdlib>
#include <deque>
#include <mutex>
#include <random>
#include <thread>
#include <vector>
#include <hpc/aux/slices.hpp>
#include <hpc/matvec/gematrix.hpp>
#include <hpc/matvec/iterators.hpp>
#include <hpc/matvec/print.hpp>

using namespace hpc;
using namespace hpc::aux;
using namespace hpc::matvec;

template<typename T>
struct RandomEnginePool {
      using EngineType = T;
      T get() {
         /* check if we have a free engine in the unused deque */
         {
            std::lock_guard<std::mutex> lock(mutex);
            if (unused.size() > 0) {
               T rg = unused.front();
               unused.pop_front();
               return rg;
            }
         }
         /* prepare new random generator */
         return T(r());
      }
      void free(T engine) {
         std::lock_guard<std::mutex> lock(mutex);
         unused.push_back(engine);
      }
   private:
      std::mutex mutex;
      std::random_device r;
      std::deque<T> unused;
};

template <
   template<typename> class MatrixA, typename T,
   typename POOL,
   Require< Ge<MatrixA<T>> > = true
>
void randomInit(MatrixA<T>& A, POOL& pool) {
   std::uniform_real_distribution<double> uniform(-100, 100);
   auto engine = pool.get();

   for (auto [i, j, Aij]: A) {
      Aij = uniform(engine);
      (void) i; (void) j; // suppress gcc warning
   }
   pool.free(engine);
}

int main() {
   RandomEnginePool<std::mt19937> pool;
   GeMatrix<double> A(51, 7);
   std::size_t nof_threads = std::thread::hardware_concurrency();

   std::vector<std::thread> threads(nof_threads);
   UniformSlices<std::size_t> slices(nof_threads, A.numRows());
   for (std::size_t index = 0; index < nof_threads; ++index) {
      auto firstRow = slices.offset(index);
      auto numRows = slices.size(index);
      auto A_ = A.view(firstRow, 0, numRows, A.numCols());
      threads[index] = std::thread([A_=std::move(A_),&pool]() mutable {
	 randomInit(A_, pool);
      });
   }
   for (std::size_t index = 0; index < nof_threads; ++index) {
      threads[index].join();
   }
   print(A, " %7.2f");
}

theon$ g++ -O3 -g -I/home/numerik/pub/hpc/ws19/session16 -std=c++17 -o random_init10 random_init10.cpp
theon$ ./random_init10
  -24.04   47.38  -72.74   57.80  -85.11  -84.66   98.82
   50.75   98.13   99.91   54.93  -56.83  -79.75  -52.36
   25.02   47.73   45.08   48.16   52.64  -42.83   69.48
  -88.75  -90.23   19.15   98.06  -89.66   29.77   77.73
  -19.76  -86.85  -49.53  -32.96  -43.49  -66.10  -52.73
  -90.09   49.00  -13.48    0.30  -69.23   59.17    4.43
   78.37  -70.87   43.04  -91.43  -23.96  -86.89   63.51
  -13.55  -43.34   71.24   53.28  -49.78   32.39  -10.94
  -16.25   48.17  -74.11  -97.07  -61.55    2.01   75.02
   39.83   73.68   74.73  -24.32   11.13   72.69   66.54
   41.07   52.83   54.48   56.76   68.39  -43.98  -50.92
   11.04   91.38   62.01  -31.55  -78.97   25.52  -32.83
  -88.98   63.50    3.91  -69.68  -36.28  -87.11    2.23
   23.37  -85.88   45.75   30.24   69.69  -11.56  -18.61
    4.81  -90.91  -57.79  -49.91  -25.23  -55.06  -58.27
   85.62  -13.22  -11.87   23.95   88.97  -14.11   42.03
    8.31   38.79  -11.11  -72.67  -34.38   75.80  -47.06
    4.74   44.38   -6.59  -97.58   83.14  -67.69  -48.69
   74.01   71.83   69.94   42.08  -25.53   96.11  -66.21
   46.82   -1.92  -59.84  -73.77  -26.10  -93.19   77.56
   -6.66   81.38   84.79  -70.83   94.99  -15.21   33.24
   19.80  -66.63  -76.10   74.76    9.04  -72.65   79.05
  -36.66  -47.38  -85.07   11.40  -11.14   11.58   71.48
  -39.51  -54.63   13.68  -94.26  -91.28  -57.70   68.74
   97.17  -89.17   45.83   74.04  -60.32   36.41   23.87
  -45.53   69.43  -78.12   40.24   81.75  -10.40   -2.58
  -32.13  -81.44  -79.59  -17.63  -62.43   -2.91   48.18
  -51.19   -1.61  -14.36   70.72   43.77  -75.66   73.14
   -0.72   35.04  -37.56   38.15   -1.35  -36.79   90.86
   26.65  -21.82    7.97  -54.53   73.79   97.93   49.37
  -29.67   -2.14  -93.65   30.58   70.17  -49.93  -89.98
   23.66  -17.49   46.96  -77.50   51.63   75.91   36.47
  -20.85   38.88   40.74   26.81   52.96   81.86   17.36
  -79.03   96.10   -9.25   11.07   13.17  -70.36   20.09
  -21.45   86.99    1.01   86.29  -40.88  -49.07   -4.42
  -35.84  -10.12   95.30   27.11  -76.42  -39.60   16.16
  -50.76   83.59  -18.35  -44.52   85.63  -43.83   94.04
   48.16    4.53   65.20  -62.40  -89.26  -69.41   89.07
  -16.23   10.72  -28.68  -89.97   27.00  -69.47   15.22
   82.99  -53.07   95.37   -2.83   93.43  -13.17    4.34
   88.75   -7.70  -66.66  -49.16  -31.04   20.17   -2.11
  -36.67   95.90   57.88  -35.56  -50.57    7.67   -0.50
    7.01   -7.51  -91.70   89.44   47.14  -37.10   23.32
   -7.59   35.70   75.63   76.00   58.68   11.25  -19.92
  -52.14    7.31   76.97  -11.73  -56.35  -68.93   84.65
   85.79  -82.21  -52.35    0.68  -52.36    2.71   93.22
   35.40   48.44  -65.11  -81.75   64.63  -34.23  -84.81
   29.73  -83.68  -83.73  -44.26  -40.55   50.69   10.72
   76.49  -77.60  -24.57  -68.34   83.74    5.95   42.00
  -71.81  -37.66   62.33   96.07  -89.10  -30.31  -38.62
    8.30   82.51   88.57   17.80  -48.39  -35.60  -38.13
theon$

heim$ g++-8.3 -O3 -g -I/home/numerik/pub/hpc/ws19/session16 -std=c++17 -o random_init10 random_init10.cpp -lpthread
heim$ ./random_init10
    4.72   57.30   96.96  -68.86    3.07   27.10   54.52
  -83.94  -68.92  -84.34   33.78   95.92  -70.08   -8.33
  -28.38    2.09   86.27   26.04   97.17  -61.02   -0.84
   42.03  -61.46    8.55   73.30  -78.91   61.57   22.86
   21.44  -11.24   63.64   74.63  -77.68   21.76   80.40
   41.75  -46.72   96.38  -46.14   13.38   18.64  -39.68
   73.34   38.29  -69.49   23.96  -44.04   30.38  -87.94
  -61.94  -96.36   99.64   70.16    7.85  -25.52   -4.65
   29.71   12.30   78.46  -84.71    7.34   84.84  -60.34
   86.62   86.73   -7.83   21.70   66.33   -2.09   59.43
   57.82  -71.43   76.76  -17.99  -94.93  -14.80  -19.97
   61.35  -84.48  -39.64    4.13  -59.88  -24.23    8.83
  -19.98  -78.60  -58.02  -62.76   66.63   -9.55  -14.62
   27.18  -31.97   19.33   -2.44  -38.41  -29.35   42.72
  -71.74   16.68    9.03  -30.27  -85.40  -31.68   80.56
    0.45    2.98  -92.25   76.17   54.15   28.09    0.43
   24.84  -40.08   87.24  -65.99  -73.40   96.86   29.94
   66.03   23.93    1.28   -6.86  -85.82   68.40   15.95
   19.47    2.50   19.60  -47.61   25.69  -73.90  -43.38
   26.55  -99.37  -61.43  -40.79    7.19   21.13    9.97
   54.39    0.56  -73.96   92.63  -62.93   38.97   65.61
   73.36  -36.86   92.77  -94.17   90.27  -30.22  -97.31
    8.25  -70.43  -94.90    1.76   51.70   87.89  -13.84
   -5.82   30.59  -94.16    0.32  -36.15  -40.71   52.23
  -33.24   73.36   89.48  -62.76  -12.39  -22.19   63.26
   54.40   -4.14   65.34   79.24  -21.08   60.87  -59.87
  -41.50  -41.25   26.65  -13.87  -93.20   58.61   -5.03
  -80.24   48.05  -91.67  -31.24   22.06  -56.25   75.28
  -14.53   78.12  -61.64   -6.54  -84.77   64.01  -58.10
   73.56   21.25   -3.31   82.24  -56.50  -50.07  -75.70
   36.62  -32.86  -94.04   35.74  -44.22   88.00  -40.91
   53.72  -71.00   56.29   64.95    6.12   33.66   -0.73
   -0.81  -49.67   -8.17  -86.78   44.75   83.53   13.70
  -14.97   -7.31   69.92  -89.04   44.40  -33.22  -36.07
  -39.70   20.89   68.29  -55.87  -94.40  -70.91  -27.49
   47.30  -11.06  -50.86   97.56   18.57   72.01  -39.25
   -2.88   78.87  -60.59   30.90   75.37  -70.12   48.83
   45.79   71.89  -84.22  -32.19   77.85   43.12  -39.83
   25.39  -65.53   33.10  -14.33  -27.43   57.70   58.81
   34.18   61.07   69.86   98.61   73.47   63.11   19.74
   11.88  -98.00   40.26  -44.49  -50.49    8.81  -33.73
  -70.25  -65.32   37.79  -48.34  -82.64   80.27  -50.12
   18.61   33.58   -4.53   20.69  -97.04  -29.17   77.25
   75.72  -19.27   18.20   12.46  -42.22   76.57   48.77
   57.31  -11.45  -66.20    3.01  -64.23    4.91  -86.60
  -97.97   45.34   17.44  -77.39   66.20   79.05  -91.65
  -46.14   31.21  -96.73   54.34  -45.10  -61.17  -56.74
  -62.95   53.05   32.05    4.11  -82.42   91.16   94.29
   53.81  -40.03   -3.06   64.44  -89.70  -29.41  -68.78
  -65.57  -68.21    9.73   33.02   48.03   28.81   -9.22
   24.51  -16.68  -50.61   72.96   96.36  -82.79  -62.97
heim$