Bonus HTC Exercise 2.4: Submit With “queue matching”

Exercise Goal

The goal of this exercise is to submit many jobs from a single submit file by using the queue ... matching syntax to submit jobs with variable values derived from files in the current directory which match a specified pattern.

Counting Words in Files

Returning to our book word-counting example, let's pretend that instead of three books, we have an entire library. While we could list all of the text files in a books.txt file and use queue book from books.txt, it could be a tedious process, especially for tens of thousands of files. Luckily HTCondor provides a mechanism for submitting jobs based on pattern-matched files.

Queue Jobs By Matching Filenames

This is an example of a common scenario: We want to run one job per file, where the filenames match a certain consistent pattern. The queue ... matching statement is made for this scenario.

Let’s see this in action. First, here is a new version of the script (note, we removed the 'top n words' restriction):

#!/usr/bin/env python3

import os
import sys
import operator

if len(sys.argv) != 2:
    print(f'Usage: {os.path.basename(sys.argv[0])} DATA')
    sys.exit(1)
input_filename = sys.argv[1]

words = {}

with open(input_filename, 'r') as my_file:
    for line in my_file:
        line_words = line.split()
        for word in line_words:
            if word in words:
                words[word] += 1
            else:
                words[word] = 1

sorted_words = sorted(words.items(), key=operator.itemgetter(1))
for word in sorted_words:
    print(f'{word[0]} {word[1]:8d}')

To use the script:

1. Create and save this script as wordcount.py.
2. Verify the script by running it on one book manually.
3. Create a new submit file to submit one job (pick a book file and model your submit file off of the one above)

4. Modify the following submit file statements to work for all books:

   transfer_input_files = $(book) 
   arguments = $(book) 
   output = $(book).out 
   error = $(book).err 
   queue book matching *.txt
   

   Note

   As always, the order of statements in a submit file does not matter, except that the queue statement should be last. Also note that any submit file variable name (here, book, but true for process and all others) may be used in any mixture of upper- and lowercase letters.

5. Submit the jobs.

HTCondor uses the queue ... matching statement to look for files in the submit directory that match the given pattern, then queues one job per match. For each job, the given variable (e.g., book here) is assigned the name of the matching file, so that it can be used in output, error, and other statements.

The result is the same as if we had written out a much longer submit file:

...

transfer_input_files = AAiW.txt
arguments = "AAiW.txt"
output = AAiW.txt.out
error = AAiW.txt.err
queue

transfer_input_files = PandP.txt
arguments = "PandP.txt"
output = PandP.txt.out
error = PandP.txt.err
queue

transfer_input_files = TAoSH.txt
arguments = "TAoSH.txt"
output = TAoSH.txt.out
error = TAoSH.txt.err
queue

...

How many jobs were created? Is this what you expected? If you ran this in the same directory as Exercise 2.3, you may have noticed that a job was submitted for the books_n.txt file that holds the variable values in the queue from statement. Beware the dangers of matching more files than intended! One solution may be to put all of the books into an books directory and queue matching books/*.txt. Can you think of other solutions? If you have time, try one!

Extra Challenge 1

In the example above, you used a single log file for all three jobs. HTCondor handles this situation with no problem; each job writes its events into the log file without getting in the way of other events and other jobs. But as you may have seen, it may be difficult for a person to understand the events for any particular job in the combined log file.

Create a new submit file that works just like the one above, except that each job writes its own log file.

Extra Challenge 2

Between this exercise and the previous one, you have explored two of the three primary queue statements. How would you use the queue in ... list statement to accomplish the same thing(s) as one or both of the exercises?