Multi tool use

Clash Royale CLAN TAG

Error when accessing an Excel workbook from within a parallel loop

I am using MATLAB to write to an Excel file with Macros in them, and then reevaluate the file and extract the Macro results using xlsread. The code works fine with only one worker. However, if I use parfor and use a second worker, MATLAB gives the error message as below. To be rigorous, I have created a second Excel file for the second worker and use t = getCurrentTask(); t.ID; to instruct the workers to work on their arranged excel file.

xlsread

parfor

t = getCurrentTask(); t.ID;

Error using xlswrite (line 226)

Invoke Error, Dispatch Exception:
Source: Microsoft Excel
Description: Microsoft Excel cannot access the file
'C:Users-----D0481000'. There are several
possible reasons:
• The file name or path does not exist.
• The file is being used by another program.
• The workbook you are trying to save has the same name as a currently open workbook.
Help File: xlmain11.chm
Help Context ID: 0

Error in extractFromExcelExpress (line 249)
xlswrite(filename,writtenIn,sheet,'B23');

This happens randomly. I did try to change the folder of the excel files and it starts to work for hours but ultimately stops. I did clear all the add-ins in Excel and I did put the corresponding folder to the excel trust locations.

The Excel version: 2016

The MATLAB version: R2017a

1 Answer
1

This sounds like a typical race condition issue caused by multiple processes requiring exclusive access to the same file. The basic idea is that one process still hasn't closed the file when another tries to open it, and you only get errors sometimes because these issues don't always occur (see also: Heisenbug).

Here are several suggestions regarding what you can do (in decreasing order of what makes sense to me):

xlswrite

parfor

parfor

xlswrite1

Workbook.MultiUserEditing

xlswrite

while true, try, xlswrite(...); break; catch, pause(0.01); end, end

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