如何使用OpenMp并行写入文件

Question

我有以下代码在Serial中完美运行：

while(fread(in, sizeof(in), 1, fp_input) && ++count){              
      Encode();
      fseek(fp_out, (count-1)*sizeof(out), SEEK_SET);
      fwrite(out, sizeof(out), 1, fp_out);
      time_spent = (double)(stop - start)/CLOCKS_PER_SEC;   
}

为了并行化代码，我使用以下OpenMP指令：

#pragma omp parallel private(in, out)
   {   
      while(read(fd_read, in, sizeof(in)) && ++count){ 
         Encode(); //take input from in and writes to out
         fseek(fp_out, (count-1)*sizeof(out), SEEK_SET);
         fwrite(out, sizeof(out), 1, fp_out);
         time_spent = (double)(stop - start)/CLOCKS_PER_SEC;   
      }   
   }   

必须保持命令作为写入输出文件，以便以后可以解密。但是我无法实现它，如何构造OpenMp指令来实现文件写入顺序？

将代码更新为以下内容，并在序列代码中获得了显着的加速：

while(fread(chunk_input, sizeof(chunk_input), 1, fp_input) == 1){ 
      int block_no = 0;
      #pragma omp parallel for private(block_no)
      for(block_no=0; block_no<CHUNK_SIZE; block_no += 16){
         unsigned char in[16], out[16];
         memcpy(in, &chunk_input[block_no], 16);          
         Encode(in, out);
         memcpy(&chunk_output[block_no], out, 16);
      }          
      fwrite(chunk_output, sizeof(chunk_output), 1, fp_out);
   }