Irrespective of the FB part, the article made me hypothesize about the actual algorithmic changes that caused this problem.
My first hypothesis was to think, Ok, the old algorithm had a hard limit on (no of re-calculations/executions of the calculating function) and with the new algorithm that was removed..
Almost immediately, i realized that’s the brute force first idea, but not likely to be true. An organization as big as NASDAQ, grew up that big with having some set of processes. There ought to have been atleast 2 stages(code review and/or pre-prod testing(i don’t really buy that it’s hard to simulate these conditions excuse in this case. The algorithm was designed to calculate pre-IPO prices based on bids by traders. I might buy there was a Fermi estimate on the max. load (while simulation) which was exceeded by facebook IPO)) which noticed that simple a blunder.
The more likely change would have been than that the developer wrote a different termination condition and managed to convince everyone involved and the process that the new termination condition is better and does ensure termination. Now this is where my lack of knowledge of the actual algorithm/code hinders any progress. The article doesn’t say but implies it was written in java and run on a jvm. But that doesn’t help much, given i really haven’t worked on java for a long time.
I would love to know, what/how it went, but have no way of finding out. So am just calling out to people who have better knowledge of the jvm to expand on the more likely change.
Please comment your ideas/suggestions.
This started out as a list of top Computer Science blogs, but it more closely resembles a set: the order is irrelevant and there are no duplicate elements; membership of this set of blogs satisfies all of the following conditions:
- they are written by computer scientists and focus on computer science research;
- they are of consistently high quality;
- I regularly read them.
N.B. I have deliberately excluded blogs primarily focusing on computer science education (for another time).
- The Endeavour by John D. Cook (@JohnDCook)
John’s blog cuts across using computing, programming and mathematics to solve real-world problems, pulling in his wide expertise as a mathematics professor, programmer, consultant, manager and statistician. Some great posts across the technical and socio-technical spectrum. Also runs a number of useful Twitter tip accounts, including @CompSciFact, @UnixToolTip, @RegexTip and @TeXtip.
- Serious Engineering by Anthony Finkelstein (@profserious)
Anthony is Dean of the Faculty of…
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When you’re designing a performance-sensitive computer system, it is important to have an intuition for the relative costs of different operations. How much does a network I/O cost, compared to a disk I/O, a load from DRAM, or an L2 cache hit? How much computation does it make sense to trade for a reduction in I/O? What is the relative cost of random vs. sequential I/O? For a given workload, what is the bottleneck resource?
When designing a system, you rarely have enough time to completely build two alternative designs to compare their performance. This makes two skills useful:
- Back-of-the-envelope analysis. This essentially means developing an intuition for the performance of different alternate designs, so that you can reject possible designs out-of-hand, or choose which alternatives to consider more carefully.
- Microbenchmarking. If you can identify the bottleneck operation for a given resource, then you can construct a micro-benchmark…
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Never use hclstore.in to buy anything. They are a non-functioning organization. Here’s why:
1. Once you order(on 7th of april) you get an email invoice that has all the columns(order no,,date,name etc…) but all empty. Their invoice generation program is broken.
2. If you call up the sales team,(on 9th of april).they assure me it will be shipped within 7-12 working days.
3. I check the card statement(around 15th of April) and find it has not been billed. So assume it’s a failed order (even though the account still shows a successful order and shrug. stupid me should have called up the bank and cancelled the transaction.)
4. Month end arrives and i see i have been billed on 18th of April for the first EMI.So I call up the sales team, they redirect you to some invoice team no, which seems unmanned. i.e: nobody picks up
5. I ask the sales team how do i cancel, and they say send a mail. I do so (30th April).No reply(as on 2nd May). Now am stuck. I guess this is one of those cases where, i’ll have to go to the consumer court to reverse the transaction. Darn it…. stupid me..
6. I called up the only number i could reach and he says, it’s up to the logistics department. they can’t do anything because the order is not in their system. i say okay, just transfer me to your logistics department, don’t ask me to hang up and call another number. He ignores and says, sir you’ve sent an email right, they will cancel.just send another email, i ask how many times i have to do that and he hangs up.. SOB.. hangs up on me ..$%#&$
7. I send an email to hclstore.in on(30th April and 2nd may) about cancelling the order and reminding them. No response
8. And I send another reminder mail with a link to this blog post and cc it to firstname.lastname@example.org today(03-May-2012). Finally they call up from the logistics department telling me the courier guy could not deliver it whenever he tried and asking me if the address is right. I tell them, am not interested anymore and can you please cancel the order. Ofcourse, they apologise for the delay deeply and ask if they can make up for it by giving a gift of a pair of external speakers(worth 3k). I say, no thank you, i have gotten ahead and got a laptop already, so i don’t need an extra one. Please cancel the order. They confirm i have sent an email and promise to do the same and call me back tommorrow.
Phew…. It feels like a huge relieving victory. And as much of a relief as it is from the anxiety over the last month, it concerns me that i have to jump through so many hoops to just get something that i think should be called basic business etiquette.