MPI_Scatter 二维向量

Question

我需要将向量的片段传递给所有进程以对矩阵进行乘法运算。我想传递一个向量（orginal_size/processes）的向量。

    std::vector<double> Algorytm::mnozenie(std::vector< std::vector <double> >  matrix,std::vector<double> wektor){
        std::vector<double> wynik(matrix.size(),0);
       if (rozmiar_macierzy_==(int)wektor.size()){
           int size=matrix.size();
           int world_size;
           MPI_Comm_size(MPI_COMM_WORLD, &world_size);
          MPI_Bcast(&size,1 , MPI_INT,0,MPI_COMM_WORLD);
          MPI_Bcast(&wektor.front(),wektor.size() , MPI_DOUBLE,0,MPI_COMM_WORLD);

          std::vector< std::vector <double> > fragment_of_matrix(matrix.size()/world_size);
          std::vector <double> tmp(size);
          for(int i=0;i<fragment_of_matrix.size();i++){
            fragment_of_matrix.at(i)=tmp;
          }
          int small_size=matrix.size()*matrix.at(0).size()/world_size;

          std::vector<double> wektor2(wektor.size()/world_size);
         // This works
         MPI_Scatter(&wektor.front(),wektor.size()/world_size , MPI_DOUBLE,&wektor2.front(),wektor.size()/world_size , MPI_DOUBLE, 0,MPI_COMM_WORLD);
         //This doesn't :(
         MPI_Scatter(&matrix.front(),small_size,  MPI_DOUBLE,&fragment_of_matrix.front(), small_size,  MPI_DOUBLE, 0,MPI_COMM_WORLD);


     }
     else{
         std::cout << "[ERROR]:"<<std::endl;
     }
     return wynik;
  }

MPI_Scatter(&matrix.front() ... 导致错误：

orrMPI(38789,0x7fff76af2000) malloc: *** error for object 0x3ff0000000000000: pointer being freed was not allocated
*** set a breakpoint in malloc_error_break to debug
[MBP-2:38789] *** Process received signal ***
[MBP-2:38789] Signal: Abort trap: 6 (6)
[MBP-2:38789] Signal code:  (0)
[MBP-2:38789] [ 0] porrMPI(38788,0x7fff76af2000) malloc: *** error for object 0x7f8b618da200: pointer being freed was not allocated
*** set a breakpoint in malloc_error_break to debug
fragment_macierzy rozmiar: 75x150 0   libsystem_platform.dylib            0x00007fff8c29feaa _sigtramp + 26
[MBP-2:38789] [ 1] 0   ???                                 0x0000000000000000 0x0 + 0
[MBP-2:38789] [ 2] 0   libsystem_c.dylib                   0x00007fff975696e7 abort + 129
[MBP-2:38789] [ 3] 0   libsystem_malloc.dylib              0x00007fff8e66c070 free + 425
[MBP-2:38789] [ 4] 0   porrMPI                             0x0000000101e77bed _ZNSt3__113__vector_baseIdNS_9allocatorIdEEED2Ev + 509
[MBP-2:38789] [ 5] 0   porrMPI                             0x0000000101e779e5 _ZNSt3__16vectorIdNS_9allocatorIdEEED2Ev + 21
[MBP-2:38789] [ 6] 0   porrMPI                             0x0000000101e727b5 _ZNSt3__16vectorIdNS_9allocatorIdEEED1Ev + 21
[MBP-2:38789] [ 7] 0   porrMPI                             0x0000000101e77d33 _ZNSt3__113__vector_baseINS_6vectorIdNS_9allocatorIdEEEENS2_IS4_EEED2Ev + 275
[MBP-2:38789] [ 8] 0   porrMPI                             0x0000000101e77c15 _ZNSt3__16vectorINS0_IdNS_9allocatorIdEEEENS1_IS3_EEED2Ev + 21
[MBP-2:38789] [ 9] 0   porrMPI                             0x0000000101e727f5 _ZNSt3__16vectorINS0_IdNS_9allocatorIdEEEENS1_IS3_EEED1Ev + 21
[MBP-2:38788] *** Process received signal ***
[MBP-2:38788] Signal: Abort trap: 6 (6)
[MBP-2:38788] Signal code:  (0)
[MBP-2:38788] [ 0] 0   libsystem_platform.dylib            0x00007fff8c29feaa _sigtramp + 26
[MBP-2:38788] [ 1] 0   ???                                 0x0000ffff00001fa0 0x0 + 281470681751456
[MBP-2:38788] [ 2] 0   libsystem_c.dylib                   0x00007fff975696e7 abort + 129
[MBP-2:38788] [ 3] 0   libsystem_malloc.dylib              0x00007fff8e66c070 free + 425
[MBP-2:38788] [ 4] 0   porrMPI                             0x000000010b4cdbed _ZNSt3__113__vector_baseIdNS_9allocatorIdEEED2Ev + 509
[MBP-2:38788] [ 5] 0   porrMPI                             0x000000010b4cd9e5 _ZNSt3__16vectorIdNS_9allocatorIdEEED2Ev + 21
[MBP-2:38788] [ 6] 0   porrMPI                             0x000000010b4c87b5 _ZNSt3__16vectorIdNS_9allocatorIdEEED1Ev + 21
[MBP-2:38788] [ 7] 0   porrMPI                             0x000000010b4cdd33 _ZNSt3__113__vector_baseINS_6vectorIdNS_9allocatorIdEEEENS2_IS4_EEED2Ev + 275
[MBP-2:38788] [ 8] 0   porrMPI                             0x000000010b4cdc15 _ZNSt3__16vectorINS0_IdNS_9allocatorIdEEEENS1_IS3_EEED2Ev + 21
[MBP-2:38788] [ 9] 0   porrMPI                             0x000000010b4c87f5 _ZNSt3__16vectorINS0_IdNS_9allocatorIdEEEENS1_IS3_EEED1Ev + 21
[MBP-2:38788] [10] 0   porrMPI                             0x000000010b4d48d1 _ZN17AlgorytmCzebyszew19obliczMacierzRownanEv + 8289
[MBP-2:38788] [11] 0   porrMPI                             0x000000010b4d7f78 main + 504
[MBP-2:38788] [12] 0   libdyld.dylib                       0x00007fff976475ad start + 1
[MBP-2:38788] [13] 0   ???                                 0x0000000000000001 0x0 + 1
[MBP-2:38788] *** End of error message ***
[MBP-2:38789] [10] 0   porrMPI                             0x0000000101e8235c _Z5slavev + 700
[MBP-2:38789] [11] 0   porrMPI                             0x0000000101e81e54 main + 212
[MBP-2:38789] [12] 0   libdyld.dylib                       0x00007fff976475ad start + 1
[MBP-2:38789] [13] 0   ???                                 0x0000000000000001 0x0 + 1
[MBP-2:38789] *** End of error message ***
--------------------------------------------------------------------------
mpiexec noticed that process rank 0 with PID 38788 on node MBP-2 exited on signal 6 (Abort trap: 6).

如何正确地将此二维向量块传递给所有进程？

Answer 1

二维向量不连续。因此，在计算 small_size 时，您可能会得到向量的确切大小，但地址在内存中并不连续。因此，当您尝试 MPI_Scatter 时，可能会在不可用的地址上执行分散操作。

解决此问题的唯一选择；

从二维向量矩阵创建一个单维向量 temp_matrix。并且，再对temp_matrix进行分散操作。确保接收器也有 1-d temp_matrix。这个解决方案几乎就像将二维向量转换为数组并执行分散操作，然后再从数组返回向量。

但是，如果向量的大小将变得巨大，这将是最愚蠢的解决方案。我希望这对你来说不是问题，因为如果一个 PE（这里是主 PE 0）可以容纳完整的 matrix 向量，那么大小不应该那么大.

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