为什么Matlab在大量迭代中缓慢进行循环，但快速迭代次数很少？

Question

我正在运行一个函数，以从100,000+个患者xray dicom文件中提取一些信息。出于安全目的，文件存储在veracrypt加密容器内。

当我运行一小部分文件时，它的执行速度非常快，但是当我在整个数据集上运行函数时，它的速度相当慢，从每秒几个文件到每秒1个文件（大约）。

，我很困惑，为什么发生这种情况？我曾尝试将数据存储在ssd和普通硬盘上，并且在使用较大数据集时与使用较小数据集相比，速度较慢。

我已经添加下面的参考代码，但还没有完全注释它尚未..这是我的论文，所以我将做到这一点，一旦我得到完成提取..

感谢您的帮助。

function [ DB, corrupted_files ] = extract_from_dcm(folder_name) 
%EXTRACT_FROM_DCM Summary of this function goes here 
% Detailed explanation goes here 

if nargin == 0 
    folder_name = 'I:\Find and Treat\MXU Old Backup\2005'; 
end 

Database_Check = strcat(folder_name, '\DataBase.mat'); 

if exist(Database_Check, 'file') 

    load(Database_Check); 
    entry_start = length(DB) + 1; 

else 

    entry_start = 1; 
    [ found_dicoms ] = recursive_search(folder_name); 

end 

mat_file_location = strcat(folder_name, '\DataBase.mat'); 
excel_DB_file = strcat(folder_name, '\DataBase.xlsx'); 
excel_Corrupted_file = strcat(folder_name, '\Corrupted_Files.xlsx'); 

% the recursive search creates a struct with the path for each 
% dcm file found. the list is then recursivly used to locate 
% the image and extract the relevant information from it. 


fprintf('---------------------------------------------\n'); 
fprintf('Start Patient Data Extraction\n'); 
tic 
h = waitbar(0,'','Name','Patient Data Extraction'); 
entry_end = length(found_dicoms); 

if entry_end == 0 
    %  set(handles.info_box, 'String', 'No Dicom Files Found in this Folder or its Subfolders'); 
else 
    %  set(handles.info_box, 'String', 'Congratulations Dicom Files have been found Look Through the Data Base using the Buttons Below....Press Save Button to save the Database. (Database Save format is EXCEL SpreadSheet and MAT file'); 

    for kk = entry_start : entry_end 
     progress = kk/entry_end; 
     progress_percent = round(progress * 100); 
     waitbar(progress,h, sprintf('%d%% %d/%d of images processed', progress_percent, kk, entry_end)); 

     img_full_path = found_dicoms(kk).name; 

     %   search_path = folder_name; 
     %   img_full_path = strrep(img_full_path, search_path, ''); 

     try    %# Attempt to perform some computation 
      dicom_info = dicominfo(img_full_path); %# The operation you are trying to perform goes here 

      try    %# Attempt to perform some computation 
       dicom_read = dicomread(dicom_info); %# The operation you are trying to perform goes here 

       old = dicominfo(img_full_path); 

       DB(kk).StudyDate = old.StudyDate; 
       DB(kk).StudyTime = old.StudyTime; 


       if isfield(old.PatientName, 'FamilyName') 
        DB(kk).Forename = old.PatientName.FamilyName; 
       else 
        DB(kk).Forename = 'NA'; 
       end 

       if isfield(old.PatientName, 'GivenName') 
        DB(kk).LastName = old.PatientName.GivenName; 
       else 
        DB(kk).LastName = 'NA'; 
       end 

       if isfield(old, 'PatientSex') 
        DB(kk).PatientSex = old.PatientSex; 
       else 
        DB(kk).PatientSex = 'NA'; 
       end 

       if isempty(old.PatientBirthDate) 
        DB(kk).PatientBirthDate = '00000000'; 
       else 
        DB(kk).PatientBirthDate = old.PatientBirthDate; 
       end 

       if strcmp(old.Manufacturer, 'Philips Medical Systems') 
        DB(kk).Van = '1'; 
       else 
        DB(kk).Van = '0';% section to represent organising by different vans 
       end 

       DB(kk).img_Path = img_full_path; 

       save(mat_file_location,'DB','found_dicoms'); 

      catch exception %# Catch the exception 
       fprintf('read - file %d corrupt.\n',kk); 
       continue  %# Pass control to the next loop iteration 
      end 



     catch exception %# Catch the exception 
      fprintf('info - file %d corrupt.\n',kk); 
      continue  %# Pass control to the next loop iteration 
     end 


    end 

end 


[ corrupted_files, DB ] = corruption_check(DB, found_dicoms, folder_name); 


toc 
fprintf('End Patient Data Extraction\n'); 
fprintf('---------------------------------------------\n'); 

fprintf('---------------------------------------------\n'); 
fprintf('Start Saving Extracted Data \n'); 
tic 


save(mat_file_location,'DB','corrupted_files','found_dicoms'); 

if isempty(DB) 
    msg = sprintf('No Dicom Files Found'); 
    msgbox(strcat(msg)); 
else 
    DB_table = struct2table(DB); 
    writetable(DB_table, excel_DB_file); 
end 

close(h); 

toc 
fprintf('End Saving Extracted Data \n'); 
fprintf('---------------------------------------------\n'); 

end 

Answer 1

OK感谢所有帮助..

我的问题是在每次迭代结束的储蓄，但最大的问题是在哪里运行dicomread功能就行了。每改变一次20张图像，我都会改变保存方式。

我也删除的意见建议，看看它没有dicromread和保存膨胀做出什么区别预分配。它比预分配要慢得多。

...我只需要找到dicomread的解决方案（我用的方法来检查，如果该文件被损坏或没有）。