how long does it take to run the match algorithm?

[josehernandez94]

i know it's a meaningless question, but a bunch of friends/colleagues and i were trying to figure out exactly how long it takes to run the match algorithm. it's more out of curiosity, but it's interesting to think that the rank list could already be determined and is just sitting in a computer database somewhere. so does anybody know how long it takes?

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[Bun]

if they have a decent computer. cant take more than ten minutes. In reality, its not all that much info to sort.

 

[mlw03]

the NRMP doesn't release this kind of info. anyone who does know it is unlikely to post it in a public forum. that said, i would agree with bun that it can't take very long for the actual algorithm to run.

 

[NotAProgDirector]

I LOVE meaningless questions.

The match algorithm is public knowledge and posted on the NRMP website. Basically, the algorithm starts by choosing any applicant and looking at their #1 rank, and "matching" them to that program if they are on the rank list. Then it takes the next applicant and does the same thing -- if when the algorithm tries to put someone into a program there is already someone on that list, they are placed on the list in the order of the program's rank list. If a program is "full", then the lowest person is bumped off the list, and the algorithm looks at their next rank, and tries to match them. This continues until all applicants are completed. Of note, it does not matter whom the algorithm starts with -- no matter what order it goes in, the final result is the same.

So, how long does this take?

The best way to guess is to count the number of iterations of the algorithm, with an "iteration" being defined as "trying to put someone on a rank list". Every time the system tries to place someone on a rank list, it could "bump" someone off the bottom of the rank list, which would generate another iteration of the algorithm. Everytime this happens, it takes more time to find a solution.

So, imagine that every applicant ranked as their #1 choice a program that listed them in the top N spots (where N=number of slots that program has). This would be a "perfect" match -- everyone gets exactly what they want. This would be the fastest option, and the number of iterations would = the number of applicants in the match.

That gives you the shortest time it takes to run the match, but is not very realistic. To better answer the question, we should look at the other extreme -- assuming the worst possible match solution, how long does it take? The "worst" solution (as far as computer computaional time is concerned) is that everyone matches into their lowest ranked position.

Rounding the numbers:
Total active applicants in 2007 = 28,000
Average length of rank list = 8 (Table 2, Charting Outcomes, "worst case")

Therefore, in a worst-case match scenario, there would be 28000 x 8 = 224,000 iterations of the match algorithm.

So, how long does it take a computer to do one iteration of the algorithm. Well, it would depend on the speed of the computer and the software being run. However, think of how fast a plain laptop can recalculate an excel spreadsheet. It would be very easy for a computer to run 10-20 iterations of the algoritm per second, and that's a very lowball estimate.

244,000 iterations / 10 per second = 24,400 seconds = 373 minutes = 6.2 hours.

And remember, that's worst case and a good computer can probably process 100's of iterations per second.

Most of the time between now and match day is double checking the data, printing, sorting, and delivering the results. Running the actual match is peanuts.

 

[hippiedoc13]

Apparently one of our deans went to a meeting at the NRMP, where he was told that it takes about 30 minutes to run the actual Match algorithm. Then they run it a number of times, to ensure that it comes out with the same results every time. It's still kinda hard to believe that it takes 3 weeks, even with all the cross-checking.

 

[XoQo]

I wonder how closely they crosscheck the repeat runs -- and what would they do if it came out differently? Which would be the "correct" one hehe.

I'm sure there's probably a bit of a historical element to the delay as i vaguely remember reading on an earlier thread that the waiting period has remained relatively constant over a span of decades while obviously computing power has increased exponentially.

I guess they want to continue their record of not having problems with the algorithm -- and avoiding what happened to the AUA match in 2005

 

[Top Gun]

Apparently one of our deans went to a meeting at the NRMP, where he was told that it takes about 30 minutes to run the actual Match algorithm. Then they run it a number of times, to ensure that it comes out with the same results every time. It's still kinda hard to believe that it takes 3 weeks, even with all the cross-checking.

Personally, I think they make us wait to torture us.

 

[prophecy2]

Common guys...what's with these whole neuroses. Everyone seems to be taking this more serious than it is...What difference does it make if you find out today or find out March 20th? These suspense and uncertainty are some of the things that make the process fun and thrilling...Think about it...

Have fun and be patience...

proph...

 

[josehernandez94]

Common guys...what's with these whole neuroses. Everyone seems to be taking this more serious than it is...What difference does it make if you find out today or find out March 20th? These suspense and uncertainty are some of the things that make the process fun and thrilling...Think about it...

Have fun and be patience...

proph...

yeah they say patient is a virtue

 

[Apollyon]

Ken Iserson in his book on residency (as he has also written a book that I can't recommend enough: Death to Dust: What Happens To Dead Bodies?) said that the match takes about 6 minutes to run. The delay between running the match and releasing the results is that it is rerun multiple times for reliability, including statistical analysis.

 

[Dre1207]

what happened to the AUA match in 2005.

What is the AUA?

 

[gutonc]

what happened to the AUA match in 2005.

What is the AUA?

AUA is the urology match which is separate from NRMP or the SF Match. I don't remember the details but it was something like program rank lists were entered backwards (i.e., the #40 person on a 40 person rank list actually ended up being ranked #1). In any event, it boiled down to people w/ AOA and PhDs going unmatched while people who barely had any business applying to rural FM programs, let alone urology, were matching at MD Anderson which is kind of messed up. The bad results actually went out too IIRC. It ended up getting re-run and all was right w/ the world.

 

[mlw03]

Common guys...what's with these whole neuroses. Everyone seems to be taking this more serious than it is...What difference does it make if you find out today or find out March 20th? These suspense and uncertainty are some of the things that make the process fun and thrilling...Think about it...

Have fun and be patience...

proph...

the difference is that i'd like to know where i'll be living for the next four years so i can start preparing to move. considering that residency starts in late june for most of us, an extra 2 weeks to prepare is not insignificant. so for me it's not neuroses, but logistics.

 

[sikegeek]

When does your home school find out where you matched? Obviously it must be earlier than 1 PM on March 20th. They have to make the envelopes and all.

When does the program you matched into find out that you matched there? I think they find out beforehand too because one of the faculty members at a residency program at my home school said that he knew who already knew who had matched there before it was released.

 

[Sharkfan]

When does your home school find out where you matched? Obviously it must be earlier than 1 PM on March 20th. They have to make the envelopes and all.

When does the program you matched into find out that you matched there? I think they find out beforehand too because one of the faculty members at a residency program at my home school said that he knew who already knew who had matched there before it was released.

At my school, the student services office workers find out where we all match either the Monday or Tuesday beforehand; they don't even go to our match ceremony because its a bit anticlimactic for them! But as far as I know they will not accept bribes to divulge the info...

 

[MonkeyRalph]

I'm pretty sure the NRMP makes the envelopes themselves and FedEx's a box full of envelopes to each school.

That would be the worst job ever. Professional envelope stuffer for the NRMP.

 

[sikegeek]

I'm pretty sure the NRMP makes the envelopes themselves and FedEx's a box full of envelopes to each school.

That would be the worst job ever. Professional envelope stuffer for the NRMP.

At out match last year, our dean was giving his preamble and said he'd seen the list and some of them should be very happy.

 

[josehernandez94]

interesting replies, thanks everyone. regardless whether the range is 6 minutes (the lowest i've seen) or 6 hours (the longest), the freaking thing has probably already been done, and several times at that. oh well. if only i had some inside connections at the nrmp headquarters.

 

[NotAProgDirector]

AUA is the urology match which is separate from NRMP or the SF Match. I don't remember the details but it was something like program rank lists were entered backwards (i.e., the #40 person on a 40 person rank list actually ended up being ranked #1). In any event, it boiled down to people w/ AOA and PhDs going unmatched while people who barely had any business applying to rural FM programs, let alone urology, were matching at MD Anderson which is kind of messed up. The bad results actually went out too IIRC. It ended up getting re-run and all was right w/ the world.

...except for the people who were told that they matched in urology, withdrew all of their GS applications / interviews, and then were told later that they didn't match in urology.

When does your home school find out where you matched? Obviously it must be earlier than 1 PM on March 20th. They have to make the envelopes and all.

When does the program you matched into find out that you matched there? I think they find out beforehand too because one of the faculty members at a residency program at my home school said that he knew who already knew who had matched there before it was released.

Programs find out the day before match day (Wednesday), but we are not allowed to tell anyone until after the match. Not sure when schools find out, but I bet it's the same. Gives them 24 hours to generate a list and have it ready for match day.

 

[Rogue_Leader]

I've asked this before, but never got a good answer. Why should the NRMP give a damn about whether the matchers and the scramblers get to have juice and cookies together on the same day of match day Thursday? I mean, it's not that the scramblers will feel better about their matches if they wait until Thursday to announce it. Information should be released as soon as it's available.

 

[josehernandez94]

I've asked this before, but never got a good answer. Why should the NRMP give a damn about whether the matchers and the scramblers get to have juice and cookies together on the same day of match day Thursday? I mean, it's not that the scramblers will feel better about their matches if they wait until Thursday to announce it. Information should be released as soon as it's available.

indeed.

 

[Lion-O]

No idea where this info came from (who knows if it's true):

http://www.themorningnews.org/archives/new_york_new_york/match_day.php

"The NRMP took control of the matching process in 1952, at the request of students who objected to the previous regime, an old boys’ network that tended to favor the well connected. Now the entire thing is done on a desktop computer running Windows XP, which with the help of a special algorithm settles everything in the space of four minutes, or about 104 lives per second. Still, in 2004, 7.1% of U.S. medical students didn’t match at all, and an even larger number ended up with something other than their first choice."

 

[NotAProgDirector]

Still, in 2004, 7.1% of U.S. medical students didn’t match at all, and an even larger number ended up with something other than their first choice."

I love how this sentence is worded to suggest that this is bad. Replace "US Medical Students" with virtually anyone else, without a match, and it's true. My favorite (off the top of my head) is "men/women looking for love".

 

[Sean2tall]

I wonder how closely they crosscheck the repeat runs -- and what would they do if it came out differently? Which would be the "correct" one hehe.

That's a good question. I'm not really sure the purpose of these repeated runs. As aprogdirector said, the match algorithm is public knowledge. As it is fairly simple in concept, it would be unacceptable if repeat runs were not all exactly 100% the same. It's not as though the computer is making a judgement call between applicants and might change its mind the second time around because it weighted your board scores a little more important than your grades.

I guess the only scenario I can imagine where two sets of results would be different is if the computer crashed midway through one attempt. Perhaps if there was a flaw in the algorithm, such as not bumping applicants off a program's list after it is tentatively filled for the first time. Although this would only evidence itself if the repeated runs started from a different name each time, which is probably a decent idea to check for this kind of error.

I guess it's worthwhile, as there is no real downside and any mismatch would alert them to a significant error in the software. Anyway, I think the short answer to that is: If there was a descrepancy between repeat runs, they would almost certainly debug the program until all repeats are the same.

On the other hand, as mentioned with the Urology match problem, with most flaws in the software algorithm, it wouldn't matter how many times you ran the program, the computer would make the same mistake every time and all lists will check out as 100% the same. So for that reason, there may be some human spot checking or something of that nature.

 

[gleep and gloop]

Common guys...what's with these whole neuroses. Everyone seems to be taking this more serious than it is...What difference does it make if you find out today or find out March 20th? These suspense and uncertainty are some of the things that make the process fun and thrilling...Think about it...

Have fun and be patience...

proph...

Like someone said above, after finding out where we match many of us are going to have to plan a move across country and find a new place to buy or rent for the next few years of our lives, all while finishing up medical school. It sucks.

Personally, I think the whole thing could easily be compressed a lot more. Finish interviews by the end of January (no more February stragglers!), have rank lists due 7-10 days later (do applicants and programs really benefit by sitting on their rank lists for 2-3 weeks between the end of interviews and the rank list deadline?), then run the algorithm, double/triple/quadruple check it, and ELECTRONICALLY send the results to the schools another week later. The registrar's office can print them out themselves for match day, and we'd have our results a month earlier.

 

[PeepshowJohnny]

Like someone said above, after finding out where we match many of us are going to have to plan a move across country and find a new place to buy or rent for the next few years of our lives, all while finishing up medical school. It sucks.

Personally, I think the whole thing could easily be compressed a lot more. Finish interviews by the end of January (no more February stragglers!), have rank lists due 7-10 days later (do applicants and programs really benefit by sitting on their rank lists for 2-3 weeks between the end of interviews and the rank list deadline?), then run the algorithm, double/triple/quadruple check it, and ELECTRONICALLY send the results to the schools another week later. The registrar's office can print them out themselves for match day, and we'd have our results a month earlier.

Love the Herculoids avatar.

My personal theory is that there's never been a big push to compress the interview and matching process because it's going to trivialize the fourth year of medical school even more.

I mean, of course, there's stilll very rampant senioritis among 4th year medical students. However, would you imagine how much it would ramp up if everybody knew by the end of January where they had matched? Students would shift their focus even more on moving on to the next phase of their lives.

Now, there's built in gaps that schools can take advantage of. "Well, I'm done with interviews and rank lists aren't due for a while, I GUESS I can just focus on this ED rotation." or "Well, rank list submitted, going to be a while before match day, nothing to do now but learn some urology"

 

[dejerine]

Happy Match to Everyone who matched. Condolences to those who did not.

 

[yippyskippy]

Hey dejerine - sorry to hear you didn't match. It sounds like you are pretty down on the world right now... I am hoping you have some good luck in the scramble (still another day to go).
Please try not to be down on aProgramDirector, though, as he is one of the most helpful things we have going on this site!! I think the "7% is not such a bad statistic" post was meant to imply that 93% of people getting to do what they wanted, even if it wasn't their very first choice, is a lot better than the odds in other areas of life... I don't think he was making negative comments about people looking for love...
Anyway, good luck... try to keep your head up!

 

[Top Gun]

Hey dejerine:

Don't be too down on yourself. I know that it sucks not getting matched, but its not over yet. You still have the scramble. And if that doesn't work, there are websites like findaresident.com which can sometimes help you find spots that are still open post-scramble. If that doesn't work, try doing some observerships/externships/research, get good letters of recommendation, and reapply to a wide variety of programs next year. And just so you know, you're not alone in not matching. On SDN, I've run across quite a few people who didn't match, some of them US grads, some of them IMG's. Keep trying all you can to get that residency. If medicine is your dream, don't give up.

 

[mosfet]

deleted post

 

[katarina]

dejerine,

Yes, you are bitter because you did not match and I don't blame you. I cannot say that I completely understand what you are going through because I am fortunate enough to have matched myself. But I empathize and sincerely wish that it turned out differently for you.

However, please do not lash out. It is neither productive nor gracious to look for someone or something to blame re: your predicament. Listing reasons why others matched (i.e. research work, good scores, money to spend) and why you did not (of course you insist it is through no fault of your own) is churlish and demeaning. I am sure that there are many medical students who did their research and also got good grades, there were also those who were on call the night before the boards and still got good scores, there are those who have even less money than you to spend on interviews and despite all of these, were still matched. Latching on to these reasons is a cop-out. It prevents you from actually asking what it is about yourself or your credentials that did not get you a spot, hence you are hindered from knowing what else you can improve. It's easier to be the victim you see, instead of taking full responsibility for a failure.

And I am highly offended by what you said about IMGs getting spots just for the sake of "diversity." That jab about Philippine graduates learning medicine from TV is misinformed, and shows how little you know about your colleagues in other countries. Newsflash: they went to medical school just like you, and they've probably seen more patients and done more procedures in a year than you've ever done in all your time in med school. IMGs work as hard or even harder for the privilege to train here. Everything about them, their grades and scores, must be above that of the average AMG to garner even half the interviews that an AMG gets. Every single one of them who matched deserve their spot as much as an AMG for all the hard work they put in. Please do not demean their well-earned achievements by saying they were matched for their ethnicity alone.

Ok, having said this (and after taking a deep breath), I still wish you well in the scramble. Perhaps after the dust has settled during this difficult time in your career/life, you will reconsider some of your comments above.

katarina

 

[dkpwalker]

dejerine,

Yes, you are bitter because you did not match and I don't blame you. I cannot say that I completely understand what you are going through because I am fortunate enough to have matched myself. But I empathize and sincerely wish that it turned out differently for you.

However, please do not lash out. It is neither productive nor gracious to look for someone or something to blame re: your predicament. Listing reasons why others matched (i.e. research work, good scores, money to spend) and why you did not (of course you insist it is through no fault of your own) is churlish and demeaning. I am sure that there are many medical students who did their research and also got good grades, there were also those who were on call the night before the boards and still got good scores, there are those who have even less money than you to spend on interviews and despite all of these, were still matched. Latching on to these reasons is a cop-out. It prevents you from actually asking what it is about yourself or your credentials that did not get you a spot, hence you are hindered from knowing what else you can improve. It's easier to be the victim you see, instead of taking full responsibility for a failure.

And I am highly offended by what you said about IMGs getting spots just for the sake of "diversity." That jab about Philippine graduates learning medicine from TV is misinformed, and shows how little you know about your colleagues in other countries. Newsflash: they went to medical school just like you, and they've probably seen more patients and done more procedures in a year than you've ever done in all your time in med school. IMGs work as hard or even harder for the privilege to train here. Everything about them, their grades and scores, must be above that of the average AMG to garner even half the interviews that an AMG gets. Every single one of them who matched deserve their spot as much as an AMG for all the hard work they put in. Please do not demean their well-earned achievements by saying they were matched for their ethnicity alone.

Ok, having said this (and after taking a deep breath), I still wish you well in the scramble. Perhaps after the dust has settled during this difficult time in your career/life, you will reconsider some of your comments above.

katarina

well said katarina, could not have said it better myself....😀

 

[urheald]

I LOVE meaningless questions.

The match algorithm is public knowledge and posted on the NRMP website. Basically, the algorithm starts by choosing any applicant and looking at their #1 rank, and "matching" them to that program if they are on the rank list. Then it takes the next applicant and does the same thing -- if when the algorithm tries to put someone into a program there is already someone on that list, they are placed on the list in the order of the program's rank list. If a program is "full", then the lowest person is bumped off the list, and the algorithm looks at their next rank, and tries to match them. This continues until all applicants are completed. Of note, it does not matter whom the algorithm starts with -- no matter what order it goes in, the final result is the same.

So, how long does this take?

The best way to guess is to count the number of iterations of the algorithm, with an "iteration" being defined as "trying to put someone on a rank list". Every time the system tries to place someone on a rank list, it could "bump" someone off the bottom of the rank list, which would generate another iteration of the algorithm. Everytime this happens, it takes more time to find a solution.

So, imagine that every applicant ranked as their #1 choice a program that listed them in the top N spots (where N=number of slots that program has). This would be a "perfect" match -- everyone gets exactly what they want. This would be the fastest option, and the number of iterations would = the number of applicants in the match.

That gives you the shortest time it takes to run the match, but is not very realistic. To better answer the question, we should look at the other extreme -- assuming the worst possible match solution, how long does it take? The "worst" solution (as far as computer computaional time is concerned) is that everyone matches into their lowest ranked position.

Rounding the numbers:
Total active applicants in 2007 = 28,000
Average length of rank list = 8 (Table 2, Charting Outcomes, "worst case")

Therefore, in a worst-case match scenario, there would be 28000 x 8 = 224,000 iterations of the match algorithm.

So, how long does it take a computer to do one iteration of the algorithm. Well, it would depend on the speed of the computer and the software being run. However, think of how fast a plain laptop can recalculate an excel spreadsheet. It would be very easy for a computer to run 10-20 iterations of the algoritm per second, and that's a very lowball estimate.

244,000 iterations / 10 per second = 24,400 seconds = 373 minutes = 6.2 hours.

And remember, that's worst case and a good computer can probably process 100's of iterations per second.

Most of the time between now and match day is double checking the data, printing, sorting, and delivering the results. Running the actual match is peanuts.

aProgDirector: That was an incredible on-the-fly analysis. Very Gregory House(esque).
You would make a great team leader in a consulting firm.

 

[nattygann01]

quote removed at user's request

I'm sorry you did not match, but honestly, I would never want you as my fellow resident if this is how you react to tough times. Apparently it is everyone's fault (from nurses to program directors to creators of the usmle) that you did not match. What role did you play in any of this? What can you do to make the best of your situation?

One of my favorite quotes...

When you are no longer able to change a situation, you are forced to change yourself"

Good luck.

 

[Top Gun]

.

 

[dejerine]

Thanks for everyone's input. Especially Yippy Skippy and TopGun (the cheerleading was great--please don't take it back)

For what it is worth, my grades were fine, I just overshot on my chances, and secy of program I wanted accidentally omitted the first day's events from my email. Also I probably didn't come off as well as I had hoped. Things happen.

I think the others who didn't match feel the same as I do, they just haven't posted.

 

[elwademd]

as has been pointed out, it takes about 10 minutes or so to run "the match".

so, for 3 weeks or so, they run it again (i guess again, again, and again), and then they run the statistics.

what i think is an intersting point, is that if they (nrmp) let the result out earlier, at least to the people whom didn't match, it would allow for perhaps a more meaningful and less stressful scramble process. after all, the medical students who haven't matched have been known for 3 weeks prior to the monday before the 3rd thursday of march. 3 weeks to scramble would be a hell of a lot better than 36 hours.

 

[elwademd]

dejerine hopefully it will all work out for you.

i know a few people that studied their asses off and got better grades than me in medical school who did not match and had to scramble. somehow, i was able to match. to me, in some ways, the match doesn't make sense. there are plenty of "variables" that can't be accounted for. not really advice, but you're definitely not alone.

 

[dejerine]

Yes, elwademd. You said it. 36 hrs is pretty abrupt to set things in order. Heard a saying, "Treat people as if they just had the worst day in their lives. About half the time, it turns out to be true!".

 

[Blade28]

Just a quick reminder for everyone to keep all discussion in this thread professional and courteous. If you have a problem with a particular user's comments, please use the PM feature to contact that him/her directly. If you feel a Terms of Service violation has occurred, use the "Report Post" feature to let the mods know.

Thanks everyone!

 

[NotAProgDirector]

what i think is an intersting point, is that if they (nrmp) let the result out earlier, at least to the people whom didn't match, it would allow for perhaps a more meaningful and less stressful scramble process. after all, the medical students who haven't matched have been known for 3 weeks prior to the monday before the 3rd thursday of march. 3 weeks to scramble would be a hell of a lot better than 36 hours.

This won't really change anything. As soon as programs know they have open spots, they will try to fill them as quickly as possible. More time won't slow the process down.

The NRMP did consider a "second match". The idea was this: run the first match. Let unmatched applicants and unfilled programs know. Give them 1 week to reapply / interview. Presumably, interviews would be via phone unless local. Unmatched applicants / unfilled programs submit a second ROL, and a second match happens. Then, there is a scramble for whatever remains unfilled.

Problem was this: The NRMP felt that in order to do this, they would need to move the ROL deadline up by a week, and move match day back by 2 weeks. That didn't go over well.