Javascript brute force search for answer to Fog Creek Software Engineering puzzle.
To discover a combination of 9 characters that when hashed with a specific algorithm would output 910897038977002.
Node.js
The application is built to systematicly sweep through all possible combinations till it finds the right one. There are a LOT of possible combinations, ~68.7 billion in fact. That being said, if the application could find the right one within 24 hours it would be considered a success.
The first goal was to build a module that could advance through combinations. This module had to consume as little memory as possible as it could be running for quite a long time. The second goal was to run through as many combinations as fast as possible. The result was a loop that could pull and test ~1,000,000/per second. Spread out over 3 running instances scanning equal parts of the combination range generated the correct answer overnight.
For long-term production use, the rough tests written here would be moved to a framework such as jasmine where they could be run as part of the application build. Additional tests would be required around the hash function as well.
[First Run]
Last attempted string = awlmaeaaa
Ended after 3,145,728 trials before allocation error.
FATAL ERROR: CALL_AND_RETRY_2 Allocation failed - process out of memory
Range 68,719,476,736.
First run only covers 0.0046% of cases.
[Second Run]
Last attempted string = cadialaaa
Pulled some local instance variables out of the while loop and tried again.
Starting rate of 13,107 per second.
Would take 60 days to Break!!!
After a few minutes, would stop continuous string of trys and started pausing after a burst of ~5-10 tries.
[Third Run]
Last attempted string = uulpcmaaa
Globalized more variables. Avoid instantiating modules multiple times in a loop.
Rate closer to 18,724 per second.
Still occasional pausing, but going to allow to run for extended time.
Starting ~7:50PM - Ending 7:55PM. 5 minutes.
[Fourth Run]
Last attempted string = unlnnptaa
Reducing number of console outputs to once every 100,000 trials.
Drasticly improves performance.
Closer to 1,048,576 per second!
Could be done in as soon as 18 HOURS!
Started ~8PM - Ended 8:05. 5 minutes.
[Fifth Run]
Last attempted string: usnnumrea
Lets try only logging every 1,000,000.
Only logs once a second or so. Trying for long term test.
Started ~8:10PM - Ended 8:30PM.
[Sixth Run]
Take out Date.now call to see how it affects performance.
Not much faster, may just let it run as performance improvements are tapering off.
Started 8:35PM - End 11:54PM.
at 9:45PM - 2,404,000,000 combinations. [ungopursa]
[Seventh Run]
Fresh sample.
Started ~11:57PM - Checked 8:33AM.
Answer found!
Divided search up in to 3 running processes. First searched starting at "aaaaaaaaa", second at "aaaaaaaai" and third started at "aaaaaaaap".
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