编写许多txt文件（90），每个文件5MB，最多需要1400秒 [英] Writing a lot of txt files (90), 5MB per file, takes up to 1400s

问题描述

我是电气工程学生。

作为一个配置，我需要实现医学成像中使用的背投影算法来形成图像。
要计算最终图像，将计算一个很多信息并保存在一个向量中。
在某个所需的分辨率（256 * 256像素）的最终图像，程序崩溃，因为我用完了RAM，所以我决定将此信息写入90个文本文件。

As an assigment I need to implement the back projection algorithm used in medical imaging to form in image. To calculate the final image a lot information is calculated and kept in a vector. At a certain desired resolution (256*256 pixels) of the final image, the program crashes as I run out of RAM, so I decided to write this information to 90 text files.

我使用stream来编写这些文件。

I use ofstream to write these file.

计算此信息，然后将其存储在向量中所需的时间是：

The time needed to calculate this information and then storing it in the vector is:

• 输出分辨率64x64：13,4s


• 输出分辨率128x128：140s

将此信息写入.txt文件中：

Writing this information in .txt files:

• 64x64 156s MB /档案）


• 128x128 1400s（5MB /档）

ofstream file;
    for(k = 0; k < 90; k++)
        {    
        oss.str(""); //string stream
        oss << "rec\\reconstruction_matrix_step"<< k << ".txt" ; // per step other file
        filename = path;
        filename.append(oss.str());
        file.open(filename.c_str());
        double weight;
          for( l = 0; l < resolution; l ++)
          {

           bestand << "Begin " << l << endl;
           l_border = - WIDTH*(resolution*1.0/2.0 - l);
           r_border = - WIDTH*(resolution*1.0/2.0 - l) + WIDTH;

           for(i = 0; i < resolution; i++)
           {
              for(j = 0; j < resolution; j++)
              {  
                     file << getSurface(pixels[i][j], l_border, r_border) << "\t";
              }
                file << "\n";
           }
           file << "End" << l << "\n\n\n";
          }
            file.close();
        }

<

When I use a vector, getSurface(pixels[i][j], l_border, r_border) is put in a vector instead of being written to a file.

有什么方法可以加快这个进程吗？

Is there any way I can speed up this proces?

推荐答案

尝试将文本格式更改为二进制格式;这可能会大大减少文件大小（和文件写入时间）。

Try changing the format from text to binary; this might reduce file size (and file writing time) greatly.

file.open(filename.c_str(), ios_base::binary);
...
// The following writes a vector into a file in binary format
vector<double> v;
const char* pointer = reinterpret_cast<const char*>(&v[0]);
size_t bytes = v.size() * sizeof(v[0]);
file.write(pointer, bytes);

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