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Wordcount Tutorial for Submitting Multiple Jobs

Imagine you have a collection of books, and you want to analyze how word usage varies from book to book or author to author.

Analyzing One Book

Test the Command

We can analyze one book by running the script, with the name of the book we want to analyze:

$ ./ Alice_in_Wonderland.txt

If you run the ls command, you should see a new file with the prefix counts which has the results of this python script. This is the output we want to produce within an HTCondor job. For now, remove the output:

$ rm counts.Alice_in_Wonderland.tsv

Create a Submit File

To submit a single job that runs this command and analyzes the Alice's Adventures in Wonderland book, we need to translate this command into HTCondor submit file syntax. The two main components we care about are (1) the actual command and (2) the needed input files.

The command gets turned into the submit file executable and arguments options:

executable =
arguments = Alice_in_Wonderland.txt

The input file for this job is the Alice_in_Wonderland.txt text file. We include that in the following submit file option:

transfer_input_files    = Alice_in_Wonderland.txt

There are other submit file options that control other aspects of the job, like where to save error and logging information, and how many resources to request per job.

This tutorial has a sample submit file (wordcount.sub) with most of these submit file options filled in:

$ cat wordcount.sub

executable = 
arguments =

transfer_input_files    =

should_transfer_files   = Yes
when_to_transfer_output = ON_EXIT

output        = logs/job.$(Cluster).$(Process).out
error         = logs/job.$(Cluster).$(Process).error
log           = logs/job.$(Cluster).$(Process).log

requirements   = (OSGVO_OS_STRING == "RHEL 7")
request_cpus   = 1
request_memory = 512MB
request_disk   = 512MB

queue 1

Open (or create) this file with a terminal-based text editor (like vi or nano) and add the executable, arguments, and input information described above.

Submit and Monitor the Job

After saving the submit file, submit the job:

$ condor_submit wordcount.submit

You can check the job's progress using condor_q. Once it finishes, you should see the same counts.Alice_in_Wonderland.tsv output.

Analyzing Multiple Books

Now suppose you wanted to analyze multiple books - more than one at a time. You could create a separate submit file for each book, and submit all of the files manually, but you'd have a lot of file lines to modify each time (in particular, the "arguments" and "transfer_input_files" line from the previous submit file).

This would be overly verbose and tedious. HTCondor has options that make it easy to submit many jobs from one submit file.

Make a List of Inputs

First we want to make a list of inputs that we want to use for our jobs. This should be a list where each item on the list corresponds to a job.

In this example, our inputs are the different text files for different books. We want each job to analyze a different book, so our list should just contain the names of these text files. We can easily create this list by using an ls command and sending the output to a file:

$ ls *.txt > book.list

Modify the Submit File

Next, we will make changes to our submit file so that it submits a job for each book title in our list (seen in the book.list file).

Create a copy of our existing submit file, that we can use for this job submission.

$ cp wordcount.sub wordcount-many.sub

Then, open the file with a text editor and go to the end. We want to tell the queue keyword to use our list of inputs to submit jobs. The default syntax looks like this:

queue from

Therefore, when we modify this syntax to fit our example, we get:

queue book from book.list

This statement works a little bit like a for loop. For every item in the book.list file, HTCondor will create a job. Each item can be referenced elsewhere in the submit file using the book variable name.

Therefore, every time we used the name of the book in our submit file (in the previous example, everywhere you see "Alice_in_Wonderland.txt") should be replaced with a variable. HTCondor's variable syntax looks like this: $(variablename)

So the following lines in the submit file should be changed to use the variable $(book):

arguments = $(book)

transfer_input_files = $(book)

Submit and Monitor the Job

We're now ready to submit all of our jobs.

$ condor_submit wordcount-many.submit

This will now submit five jobs (one for each book on our list). Once all five have finished running, we should see "counts" files for each book in the directory.