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  • What is more interesting or powerful: Curry/Mercury/Lambda-Prolog/your suggestion.

    - by Bubba88
    Hi! I would like to ask you about what formal system could be more interesting to implement from scratch/reverse engineer. I've looked through some existing and rather open (open in the sense of free/open-source) projects of logical/declarative programming systems. I've decided to make up something similar in my free time, or at least to catch the general idea of implementation. It would be great if some of these systems would provide most of the expressive power and conciseness of modern academic investigations in logic and it's relation with computational models. What would you recommend to study at least at the conceptual level? For example, Lambda-Prolog is interesting particularly because it allows for higher order relations, but AFAIK (I might really be mistaken :)) is based on intuitionist logic and therefore lack the excluded-middle principle; that's generally a disatvantage for me.. I would also welcome any suggestions about modern logical programming systems which are less popular but more expressive/powerful. I guess, this question will need refactoring, but thank you in advance! :)

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  • Why are my Opteron cores running at only 75% capacity each? (25% CPU idle)

    - by Tim Cooper
    We've just taken delivery of a powerful 32-core AMD Opteron server with 128Gb. We have 2 x 6272 CPU's with 16 cores each. We are running a big long-running java task on 30 threads. We have the NUMA optimisations for Linux and java turned on. Our Java threads are mainly using objects that are private to that thread, sometimes reading memory that other threads will be reading, and very very occasionally writing or locking shared objects. We can't explain why the CPU cores are 25% idle. Below is a dump of "top": top - 23:06:38 up 1 day, 23 min, 3 users, load average: 10.84, 10.27, 9.62 Tasks: 676 total, 1 running, 675 sleeping, 0 stopped, 0 zombie Cpu(s): 64.5%us, 1.3%sy, 0.0%ni, 32.9%id, 1.3%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 132138168k total, 131652664k used, 485504k free, 92340k buffers Swap: 5701624k total, 230252k used, 5471372k free, 13444344k cached ... top - 22:37:39 up 23:54, 3 users, load average: 7.83, 8.70, 9.27 Tasks: 678 total, 1 running, 677 sleeping, 0 stopped, 0 zombie Cpu0 : 75.8%us, 2.0%sy, 0.0%ni, 22.2%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu1 : 77.2%us, 1.3%sy, 0.0%ni, 21.5%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu2 : 77.3%us, 1.0%sy, 0.0%ni, 21.7%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu3 : 77.8%us, 1.0%sy, 0.0%ni, 21.2%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu4 : 76.9%us, 2.0%sy, 0.0%ni, 21.1%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu5 : 76.3%us, 2.0%sy, 0.0%ni, 21.7%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu6 : 12.6%us, 3.0%sy, 0.0%ni, 84.4%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu7 : 8.6%us, 2.0%sy, 0.0%ni, 89.4%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu8 : 77.0%us, 2.0%sy, 0.0%ni, 21.1%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu9 : 77.0%us, 2.0%sy, 0.0%ni, 21.1%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu10 : 77.6%us, 1.7%sy, 0.0%ni, 20.8%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu11 : 75.7%us, 2.0%sy, 0.0%ni, 21.4%id, 1.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu12 : 76.6%us, 2.3%sy, 0.0%ni, 21.1%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu13 : 76.6%us, 2.3%sy, 0.0%ni, 21.1%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu14 : 76.2%us, 2.6%sy, 0.0%ni, 15.9%id, 5.3%wa, 0.0%hi, 0.0%si, 0.0%st Cpu15 : 76.6%us, 2.0%sy, 0.0%ni, 21.5%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu16 : 73.6%us, 2.6%sy, 0.0%ni, 23.8%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu17 : 74.5%us, 2.3%sy, 0.0%ni, 23.2%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu18 : 73.9%us, 2.3%sy, 0.0%ni, 23.8%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu19 : 72.9%us, 2.6%sy, 0.0%ni, 24.4%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu20 : 72.8%us, 2.6%sy, 0.0%ni, 24.5%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu21 : 72.7%us, 2.3%sy, 0.0%ni, 25.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu22 : 72.5%us, 2.6%sy, 0.0%ni, 24.8%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu23 : 73.0%us, 2.3%sy, 0.0%ni, 24.7%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu24 : 74.7%us, 2.7%sy, 0.0%ni, 22.7%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu25 : 74.5%us, 2.6%sy, 0.0%ni, 22.8%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu26 : 73.7%us, 2.0%sy, 0.0%ni, 24.3%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu27 : 74.1%us, 2.3%sy, 0.0%ni, 23.6%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu28 : 74.1%us, 2.3%sy, 0.0%ni, 23.6%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu29 : 74.0%us, 2.0%sy, 0.0%ni, 24.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu30 : 73.2%us, 2.3%sy, 0.0%ni, 24.5%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu31 : 73.1%us, 2.0%sy, 0.0%ni, 24.9%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 132138168k total, 131711704k used, 426464k free, 88336k buffers Swap: 5701624k total, 229572k used, 5472052k free, 13745596k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 13865 root 20 0 122g 112g 3.1g S 2334.3 89.6 20726:49 java 27139 jayen 20 0 15428 1728 952 S 2.6 0.0 0:04.21 top 27161 sysadmin 20 0 15428 1712 940 R 1.0 0.0 0:00.28 top 33 root 20 0 0 0 0 S 0.3 0.0 0:06.24 ksoftirqd/7 131 root 20 0 0 0 0 S 0.3 0.0 0:09.52 events/0 1858 root 20 0 0 0 0 S 0.3 0.0 1:35.14 kondemand/0 A dump of the java stack confirms that none of the threads are anywhere near the few places where locks are used, nor are they anywhere near any disk or network i/o. I had trouble finding a clear explanation of what 'top' means by "idle" versus "wait", but I get the impression that "idle" means "no more threads that need to be run" but this doesn't make sense in our case. We're using a "Executors.newFixedThreadPool(30)". There are a large number of tasks pending and each task lasts for 10 seconds or so. I suspect that the explanation requires a good understanding of NUMA. Is the "idle" state what you see when a CPU is waiting for a non-local access? If not, then what is the explanation?

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  • Of transactions and Mongo

    - by Nuri Halperin
    Originally posted on: http://geekswithblogs.net/nuri/archive/2014/05/20/of-transactions-and-mongo-again.aspxWhat's the first thing you hear about NoSQL databases? That they lose your data? That there's no transactions? No joins? No hope for "real" applications? Well, you *should* be wondering whether a certain of database is the right one for your job. But if you do so, you should be wondering that about "traditional" databases as well! In the spirit of exploration let's take a look at a common challenge: You are a bank. You have customers with accounts. Customer A wants to pay B. You want to allow that only if A can cover the amount being transferred. Let's looks at the problem without any context of any database engine in mind. What would you do? How would you ensure that the amount transfer is done "properly"? Would you prevent a "transaction" from taking place unless A can cover the amount? There are several options: Prevent any change to A's account while the transfer is taking place. That boils down to locking. Apply the change, and allow A's balance to go below zero. Charge person A some interest on the negative balance. Not friendly, but certainly a choice. Don't do either. Options 1 and 2 are difficult to attain in the NoSQL world. Mongo won't save you headaches here either. Option 3 looks a bit harsh. But here's where this can go: ledger. See, and account doesn't need to be represented by a single row in a table of all accounts with only the current balance on it. More often than not, accounting systems use ledgers. And entries in ledgers - as it turns out – don't actually get updated. Once a ledger entry is written, it is not removed or altered. A transaction is represented by an entry in the ledger stating and amount withdrawn from A's account and an entry in the ledger stating an addition of said amount to B's account. For sake of space-saving, that entry in the ledger can happen using one entry. Think {Timestamp, FromAccountId, ToAccountId, Amount}. The implication of the original question – "how do you enforce non-negative balance rule" then boils down to: Insert entry in ledger Run validation of recent entries Insert reverse entry to roll back transaction if validation failed. What is validation? Sum up the transactions that A's account has (all deposits and debits), and ensure the balance is positive. For sake of efficiency, one can roll up transactions and "close the book" on transactions with a pseudo entry stating balance as of midnight or something. This lets you avoid doing math on the fly on too many transactions. You simply run from the latest "approved balance" marker to date. But that's an optimization, and premature optimizations are the root of (some? most?) evil.. Back to some nagging questions though: "But mongo is only eventually consistent!" Well, yes, kind of. It's not actually true that Mongo has not transactions. It would be more descriptive to say that Mongo's transaction scope is a single document in a single collection. A write to a Mongo document happens completely or not at all. So although it is true that you can't update more than one documents "at the same time" under a "transaction" umbrella as an atomic update, it is NOT true that there' is no isolation. So a competition between two concurrent updates is completely coherent and the writes will be serialized. They will not scribble on the same document at the same time. In our case - in choosing a ledger approach - we're not even trying to "update" a document, we're simply adding a document to a collection. So there goes the "no transaction" issue. Now let's turn our attention to consistency. What you should know about mongo is that at any given moment, only on member of a replica set is writable. This means that the writable instance in a set of replicated instances always has "the truth". There could be a replication lag such that a reader going to one of the replicas still sees "old" state of a collection or document. But in our ledger case, things fall nicely into place: Run your validation against the writable instance. It is guaranteed to have a ledger either with (after) or without (before) the ledger entry got written. No funky states. Again, the ledger writing *adds* a document, so there's no inconsistent document state to be had either way. Next, we might worry about data loss. Here, mongo offers several write-concerns. Write-concern in Mongo is a mode that marshals how uptight you want the db engine to be about actually persisting a document write to disk before it reports to the application that it is "done". The most volatile, is to say you don't care. In that case, mongo would just accept your write command and say back "thanks" with no guarantee of persistence. If the server loses power at the wrong moment, it may have said "ok" but actually no written the data to disk. That's kind of bad. Don't do that with data you care about. It may be good for votes on a pole regarding how cute a furry animal is, but not so good for business. There are several other write-concerns varying from flushing the write to the disk of the writable instance, flushing to disk on several members of the replica set, a majority of the replica set or all of the members of a replica set. The former choice is the quickest, as no network coordination is required besides the main writable instance. The others impose extra network and time cost. Depending on your tolerance for latency and read-lag, you will face a choice of what works for you. It's really important to understand that no data loss occurs once a document is flushed to an instance. The record is on disk at that point. From that point on, backup strategies and disaster recovery are your worry, not loss of power to the writable machine. This scenario is not different from a relational database at that point. Where does this leave us? Oh, yes. Eventual consistency. By now, we ensured that the "source of truth" instance has the correct data, persisted and coherent. But because of lag, the app may have gone to the writable instance, performed the update and then gone to a replica and looked at the ledger there before the transaction replicated. Here are 2 options to deal with this. Similar to write concerns, mongo support read preferences. An app may choose to read only from the writable instance. This is not an awesome choice to make for every ready, because it just burdens the one instance, and doesn't make use of the other read-only servers. But this choice can be made on a query by query basis. So for the app that our person A is using, we can have person A issue the transfer command to B, and then if that same app is going to immediately as "are we there yet?" we'll query that same writable instance. But B and anyone else in the world can just chill and read from the read-only instance. They have no basis to expect that the ledger has just been written to. So as far as they know, the transaction hasn't happened until they see it appear later. We can further relax the demand by creating application UI that reacts to a write command with "thank you, we will post it shortly" instead of "thank you, we just did everything and here's the new balance". This is a very powerful thing. UI design for highly scalable systems can't insist that the all databases be locked just to paint an "all done" on screen. People understand. They were trained by many online businesses already that your placing of an order does not mean that your product is already outside your door waiting (yes, I know, large retailers are working on it... but were' not there yet). The second thing we can do, is add some artificial delay to a transaction's visibility on the ledger. The way that works is simply adding some logic such that the query against the ledger never nets a transaction for customers newer than say 15 minutes and who's validation flag is not set. This buys us time 2 ways: Replication can catch up to all instances by then, and validation rules can run and determine if this transaction should be "negated" with a compensating transaction. In case we do need to "roll back" the transaction, the backend system can place the timestamp of the compensating transaction at the exact same time or 1ms after the original one. Effectively, once A or B visits their ledger, both transactions would be visible and the overall balance "as of now" would reflect no change.  The 2 transactions (attempted/ reverted) would be visible , since we do actually account for the attempt. Hold on a second. There's a hole in the story: what if several transfers from A to some accounts are registered, and 2 independent validators attempt to compute the balance concurrently? Is there a chance that both would conclude non-sufficient-funds even though rolling back transaction 100 would free up enough for transaction 117 (some random later transaction)? Yes. there is that chance. But the integrity of the business rule is not compromised, since the prime rule is don't dispense money you don't have. To minimize or eliminate this scenario, we can also assign a single validation process per origin account. This may seem non-scalable, but it can easily be done as a "sharded" distribution. Say we have 11 validation threads (or processing nodes etc.). We divide the account number space such that each validator is exclusively responsible for a certain range of account numbers. Sounds cunningly similar to Mongo's sharding strategy, doesn't it? Each validator then works in isolation. More capacity needed? Chop the account space into more chunks. So where  are we now with the nagging questions? "No joins": Huh? What are those for? "No transactions": You mean no cross-collection and no cross-document transactions? Granted - but don't always need them either. "No hope for real applications": well... There are more issues and edge cases to slog through, I'm sure. But hopefully this gives you some ideas of how to solve common problems without distributed locking and relational databases. But then again, you can choose relational databases if they suit your problem.

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  • Detect Rotation of a scanned image in C#

    - by ahmed fouad
    We want a c# solution to correct the scanned image because it is rotated. To solve this problem we must detect the rotation angle first and then rotate the image. This was our first thought for our problem. But then we thought image warping would be more accurate as I think it would make the scanned image like our template. Then we can process it as we know all the coordinates of our template... I searched for a free SDK or a free solution in c#. Helping me in this will be great as it is the last task in our work. Really, thanks for all.

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  • my server suddenly crashes every 2 days or so. Programmer has no idea, please help find the cause, here is the top

    - by Alex
    Every couple of days my server suddenly crashes and I must request hardware reset at data center to get it back running. Today I came back to my shell and saw the server was dead and "top" was running on it, and see below for the "top" right before the crash. I opened /var/log/messages and scrolled to the reboot time and see nothing, no errors prior to the hard reboot. (I checked in /etc/syslog.conf and I see "*.info;mail.none;authpriv.none;cron.none /var/log/messages" , isn't this good enough to log all problems?) Usually when I look at the top, the swap is never used up like this! I also don't know why mysqld is at 323% cpu (server only runs drupal and its never slow or overloaded). Solver is my application. I don't know whats that 'sh' doing and 'dovecot' doing. Its driving me crazy over the last month, please help me solve this mystery and stop my downtimes. top - 01:10:06 up 6 days, 5 min, 3 users, load average: 34.87, 18.68, 9.03 Tasks: 500 total, 19 running, 481 sleeping, 0 stopped, 0 zombie Cpu(s): 0.0%us, 96.6%sy, 0.0%ni, 1.7%id, 1.8%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 8165600k total, 8139764k used, 25836k free, 428k buffers Swap: 2104496k total, 2104496k used, 0k free, 8236k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 4421 mysql 15 0 571m 105m 976 S 323.5 1.3 9:08.00 mysqld 564 root 20 -5 0 0 0 R 99.5 0.0 2:49.16 kswapd1 25767 apache 19 0 399m 8060 888 D 79.3 0.1 0:06.64 httpd 25781 apache 19 0 398m 5648 492 R 79.0 0.1 0:08.21 httpd 25961 apache 25 0 398m 5700 560 R 76.7 0.1 0:17.81 httpd 25980 apache 25 0 10816 668 520 R 75.0 0.0 0:46.95 sh 563 root 20 -5 0 0 0 D 71.4 0.0 3:12.37 kswapd0 25766 apache 25 0 399m 7256 756 R 69.7 0.1 0:39.83 httpd 25911 apache 25 0 398m 5612 480 R 58.8 0.1 0:17.63 httpd 25782 apache 25 0 440m 38m 648 R 55.2 0.5 0:18.94 httpd 25966 apache 25 0 398m 5640 556 R 55.2 0.1 0:48.84 httpd 4588 root 25 0 74860 596 476 R 53.9 0.0 0:37.90 crond 25939 apache 25 0 2776 172 84 R 48.9 0.0 0:59.46 solver 4575 root 25 0 397m 6004 1144 R 48.6 0.1 1:00.43 httpd 25962 apache 25 0 398m 5628 492 R 47.9 0.1 0:14.58 httpd 25824 apache 25 0 440m 39m 680 D 47.3 0.5 0:57.85 httpd 25968 apache 25 0 398m 5612 528 R 46.6 0.1 0:42.73 httpd 4477 root 25 0 6084 396 280 R 46.3 0.0 0:59.53 dovecot 25982 root 25 0 397m 5108 240 R 45.9 0.1 0:18.01 httpd 25943 apache 25 0 2916 172 8 R 44.0 0.0 0:53.54 solver 30687 apache 25 0 468m 63m 1124 D 42.3 0.8 0:45.02 httpd 25978 apache 25 0 398m 5688 600 R 23.8 0.1 0:40.99 httpd 25983 root 25 0 397m 5272 384 D 14.9 0.1 0:18.99 httpd 935 root 10 -5 0 0 0 D 14.2 0.0 1:54.60 kjournald 25986 root 25 0 397m 5308 420 D 8.9 0.1 0:04.75 httpd 4011 haldaemo 25 0 31568 1476 716 S 5.6 0.0 0:24.36 hald 25956 apache 23 0 398m 5872 644 S 5.6 0.1 0:13.85 httpd 18336 root 18 0 13004 1332 724 R 0.3 0.0 1:46.66 top 1 root 18 0 10372 212 180 S 0.0 0.0 0:05.99 init 2 root RT -5 0 0 0 S 0.0 0.0 0:00.95 migration/0 3 root 34 19 0 0 0 S 0.0 0.0 0:00.01 ksoftirqd/0 4 root RT -5 0 0 0 S 0.0 0.0 0:00.00 watchdog/0 5 root RT -5 0 0 0 S 0.0 0.0 0:00.15 migration/1 6 root 34 19 0 0 0 S 0.0 0.0 0:00 .06 ksoftirqd/1 here is a normal top, when server is working fine: top - 01:50:41 up 21 min, 1 user, load average: 2.98, 2.70, 1.68 Tasks: 271 total, 2 running, 269 sleeping, 0 stopped, 0 zombie Cpu(s): 15.0%us, 1.1%sy, 0.0%ni, 81.4%id, 2.4%wa, 0.1%hi, 0.0%si, 0.0%st Mem: 8165600k total, 2035856k used, 6129744k free, 60840k buffers Swap: 2104496k total, 0k used, 2104496k free, 283744k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 2204 apache 17 0 466m 83m 19m S 25.9 1.0 0:22.16 httpd 11347 apache 15 0 466m 83m 19m S 25.9 1.0 0:26.10 httpd 18204 apache 18 0 481m 97m 19m D 25.2 1.2 0:13.99 httpd 4644 apache 18 0 481m 100m 19m D 24.6 1.3 1:17.12 httpd 4727 apache 17 0 481m 99m 19m S 24.3 1.2 1:10.77 httpd 4777 apache 17 0 482m 102m 21m S 23.6 1.3 1:38.27 httpd 8924 apache 15 0 483m 99m 19m S 22.3 1.3 1:13.41 httpd 9390 apache 18 0 483m 99m 19m S 18.9 1.2 1:05.35 httpd 4728 apache 16 0 481m 101m 19m S 14.3 1.3 1:12.50 httpd 4648 apache 15 0 481m 107m 27m S 12.6 1.4 1:18.62 httpd 24955 apache 15 0 467m 82m 19m S 3.3 1.0 0:21.80 httpd 4722 apache 15 0 503m 118m 19m R 1.7 1.5 1:17.79 httpd 4647 apache 15 0 484m 105m 20m S 1.3 1.3 1:40.73 httpd 4643 apache 16 0 481m 100m 20m S 0.7 1.3 1:11.80 httpd 1561 root 15 0 12900 1264 828 R 0.3 0.0 0:00.54 top 4434 mysql 15 0 496m 55m 4812 S 0.3 0.7 0:06.69 mysqld 4646 apache 15 0 481m 100m 19m S 0.3 1.3 1:25.51 httpd 1 root 18 0 10372 692 580 S 0.0 0.0 0:02.09 init 2 root RT -5 0 0 0 S 0.0 0.0 0:00.03 migration/0 3 root 34 19 0 0 0 S 0.0 0.0 0:00.00 ksoftirqd/0 4 root RT -5 0 0 0 S 0.0 0.0 0:00.00 watchdog/0 5 root RT -5 0 0 0 S 0.0 0.0 0:00.00 migration/1 6 root 34 19 0 0 0 S 0.0 0.0 0:00.00 ksoftirqd/1 7 root RT -5 0 0 0 S 0.0 0.0 0:00.00 watchdog/1 8 root RT -5 0 0 0 S 0.0 0.0 0:00.00 migration/2 9 root 34 19 0 0 0 S 0.0 0.0 0:00.00 ksoftirqd/2 10 root RT -5 0 0 0 S 0.0 0.0 0:00.00 watchdog/2 11 root RT -5 0 0 0 S 0.0 0.0 0:00.00 migration/3 12 root 34 19 0 0 0 S 0.0 0.0 0:00.00 ksoftirqd/3 13 root RT -5 0 0 0 S 0.0 0.0 0:00.00 watchdog/3 14 root RT -5 0 0 0 S 0.0 0.0 0:00.03 migration/4 15 root 34 19 0 0 0 S 0.0 0.0 0:00.00 ksoftirqd/4 16 root RT -5 0 0 0 S 0.0 0.0 0:00.00 watchdog/4 17 root RT -5 0 0 0 S 0.0 0.0 0:00.02 migration/5 18 root 34 19 0 0 0 S 0.0 0.0 0:00.00 ksoftirqd/5 19 root RT -5 0 0 0 S 0.0 0.0 0:00.00 watchdog/5 20 root RT -5 0 0 0 S 0.0 0.0 0:00.01 migration/6 21 root 34 19 0 0 0 S 0.0 0.0 0:00.00 ksoftirqd/6 22 root RT -5 0 0 0 S 0.0 0.0 0:00.00 watchdog/6 23 root RT -5 0 0 0 S 0.0 0.0 0:00.00 migration/7

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  • global static boolean pointer causes segmentation fault using pthread

    - by asksw0rder
    New to pthread programming, and stuck on this error when working on a C++&C mixed code. What I have done is to call the c code in the thread created by the c++ code. There is a static boolean pointer used in the thread and should got free when the thread finishes. However I noticed that every time when the program processed into the c function, the value of the boolean pointer would be changed and the segmentation fault then happened due to the free(). Detail code is as follows: static bool *is_center; // omit other codes in between ... void streamCluster( PStream* stream) { // some code here ... while(1){ // some code here ... is_center = (bool*)calloc(points.num,sizeof(bool)); // start the parallel thread here. // the c code is invoked in this function. localSearch(&points,kmin, kmax,&kfinal); // parallel free(is_center); } And the function using parallel is as follows (my c code is invoked in each thread): void localSearch( Points* points, long kmin, long kmax, long* kfinal ) { pthread_barrier_t barrier; pthread_t* threads = new pthread_t[nproc]; pkmedian_arg_t* arg = new pkmedian_arg_t[nproc]; pthread_barrier_init(&barrier,NULL,nproc); for( int i = 0; i < nproc; i++ ) { arg[i].points = points; arg[i].kmin = kmin; arg[i].kmax = kmax; arg[i].pid = i; arg[i].kfinal = kfinal; arg[i].barrier = &barrier; pthread_create(threads+i,NULL,localSearchSub,(void*)&arg[i]); } for ( int i = 0; i < nproc; i++) { pthread_join(threads[i],NULL); } delete[] threads; delete[] arg; pthread_barrier_destroy(&barrier); } Finally the function calling my c code: void* localSearchSub(void* arg_) { // omit some initialize code... // my code begin_papi_thread(&eventSet); // Processing k-means, omit codes. // is_center value will be updated correctly // my code end_papi_thread(&eventSet); // when jumping into this, error happens return NULL; } And from gdb, what I have got for the is_center is: Breakpoint 2, localSearchSub (arg_=0x600000000000bc40) at streamcluster.cpp:1711 1711 end_papi_thread(&eventSet); (gdb) s Hardware watchpoint 1: is_center Old value = (bool *) 0x600000000000bba0 New value = (bool *) 0xa93f3 0x400000000000d8d1 in localSearchSub (arg_=0x600000000000bc40) at streamcluster.cpp:1711 1711 end_papi_thread(&eventSet); Any suggestions? Thanks in advance!

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  • C# Abort()ing threads on exit for a Form

    - by Gio Borje
    So far I have this code run when the X button is clicked, but I'm not sure if this is the correct way to terminate threads on a form on exit. Type t = this.GetType(); foreach (PropertyInfo pi in t.GetProperties()) { if (pi.GetType() == typeof(Thread)) { MethodInfo mi = pi.GetType().GetMethod("Abort"); mi.Invoke(null, new object[] {}); } } I keep getting this error: "An attempt has been made to free an RCW that is in use. The RCW is in use on the active thread or another thread. Attempting to free an in-use RCW can cause corruption or data loss."

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  • Interoperability between two AES algorithms

    - by lpfavreau
    Hello, I'm new to cryptography and I'm building some test applications to try and understand the basics of it. I'm not trying to build the algorithms from scratch but I'm trying to make two different AES-256 implementation talk to each other. I've got a database that was populated with this Javascript implementation stored in Base64. Now, I'm trying to get an Objective-C method to decrypt its content but I'm a little lost as to where the differences in the implementations are. I'm able to encrypt/decrypt in Javascript and I'm able to encrypt/decrypt in Cocoa but cannot make a string encrypted in Javascript decrypted in Cocoa or vice-versa. I'm guessing it's related to the initialization vector, nonce, counter mode of operation or all of these, which quite frankly, doesn't speak to me at the moment. Here's what I'm using in Objective-C, adapted mainly from this and this: @implementation NSString (Crypto) - (NSString *)encryptAES256:(NSString *)key { NSData *input = [self dataUsingEncoding: NSUTF8StringEncoding]; NSData *output = [NSString cryptoAES256:input key:key doEncrypt:TRUE]; return [Base64 encode:output]; } - (NSString *)decryptAES256:(NSString *)key { NSData *input = [Base64 decode:self]; NSData *output = [NSString cryptoAES256:input key:key doEncrypt:FALSE]; return [[[NSString alloc] initWithData:output encoding:NSUTF8StringEncoding] autorelease]; } + (NSData *)cryptoAES256:(NSData *)input key:(NSString *)key doEncrypt:(BOOL)doEncrypt { // 'key' should be 32 bytes for AES256, will be null-padded otherwise char keyPtr[kCCKeySizeAES256 + 1]; // room for terminator (unused) bzero(keyPtr, sizeof(keyPtr)); // fill with zeroes (for padding) // fetch key data [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding]; NSUInteger dataLength = [input length]; // See the doc: For block ciphers, the output size will always be less than or // equal to the input size plus the size of one block. // That's why we need to add the size of one block here size_t bufferSize = dataLength + kCCBlockSizeAES128; void* buffer = malloc(bufferSize); size_t numBytesCrypted = 0; CCCryptorStatus cryptStatus = CCCrypt(doEncrypt ? kCCEncrypt : kCCDecrypt, kCCAlgorithmAES128, kCCOptionECBMode | kCCOptionPKCS7Padding, keyPtr, kCCKeySizeAES256, nil, // initialization vector (optional) [input bytes], dataLength, // input buffer, bufferSize, // output &numBytesCrypted ); if (cryptStatus == kCCSuccess) { // the returned NSData takes ownership of the buffer and will free it on deallocation return [NSData dataWithBytesNoCopy:buffer length:numBytesCrypted]; } free(buffer); // free the buffer; return nil; } @end Of course, the input is Base64 decoded beforehand. I see that each encryption with the same key and same content in Javascript gives a different encrypted string, which is not the case with the Objective-C implementation that always give the same encrypted string. I've read the answers of this post and it makes me believe I'm right about something along the lines of vector initialization but I'd need your help to pinpoint what's going on exactly. Thank you!

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  • Can I use manifests to specify an optional dependency on a COM server?

    - by sharptooth
    I'd like to use manifests to specify a dependency on a COM server (reg-free COM). The consumer application will mostly work fine without the COM server - only something like 1,7% of its functionality uses the COM server. So with plain old regsvr32 it would start and work fine until the user would do something that would trigger CoCreateInstance() call and at that point the consumer would get an error message. Now I've played with manifests for a while and it looks like the consumer wouldn't even start unless the COM server assembly it depends on is present in the file system. That's no good. Is there a way to use reg-free COM with manifests and make the dependency optional - so that the consumer program starts and works fine until CoCreateInstance() is actually called?

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  • PPV Code Review - Is it good idea?

    - by user93422
    I believe in (solo) code reviews a lot. But I am in a one-developer-shop now. I would like to have my code reviewed, and willing to pay money for it. Question: Is there a place where I can have my code reviewed for money? Note: I understand that most of us are willing to review some one else code for free, but there is a limit to how much code one (e.g. I) is willing to review for free before getting bored. Question: Is it good idea to pay 3d party to do my code-reviews?

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  • Windows Structured Exception Handling: simple test program will not compile.

    - by Jon
    #include <windows.h> int main() { int* i = (int*)malloc(sizeof(int)); *i = 5; __try { free(i); free(i); } __except { return -1; } return 0; } I am trying to learn more about windows SEH. My first test program is giving me some real trouble. I have looked at the msdn documentation and I am still not really sure what I have wrong. I am getting the following errors when I try to compile this program: error C2059: syntax error : '{' error C2143: syntax error : missing ';' before '{' both on line 15. Thanks.

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  • How to overwrite an array of char pointers with a larger list of char pointers?

    - by Casey
    My function is being passed a struct containing, among other things, a NULL terminated array of pointers to words making up a command with arguments. I'm performing a glob match on the list of arguments, to expand them into a full list of files, then I want to replace the passed argument array with the new expanded one. The globbing is working fine, that is, g.gl_pathv is populated with the list of expected files. However, I am having trouble copying this array into the struct I was given. #include <glob.h> struct command { char **argv; // other fields... } void myFunction( struct command * cmd ) { char **p = cmd->argv; char* program = *p++; // save the program name (e.g 'ls', and increment to the first argument glob_t g; memset(&g, 0, sizeof(g)); g.gl_offs = 1; int res = glob(*p++, GLOB_DOOFFS, NULL, &g); glob_handle_res(res); while (*p) { res = glob(*p, GLOB_DOOFFS | GLOB_APPEND, NULL, &g); glob_handle_res(res); } if( g.gl_pathc <= 0 ) { globfree(&g); } cmd->argv = malloc((g.gl_pathc + g.gl_offs) * sizeof *cmd->argv); if (cmd->argv == NULL) { sys_fatal_error("pattern_expand: malloc failed\n");} // copy over the arguments size_t i = g.gl_offs; for (; i < g.gl_pathc + g.gl_offs; ++i) cmd->argv[i] = strdup(g.gl_pathv[i]); // insert the original program name cmd->argv[0] = strdup(program); ** cmd->argv[g.gl_pathc + g.gl_offs] = 0; ** globfree(&g); } void command_free(struct esh_command * cmd) { char ** p = cmd->argv; while (*p) { free(*p++); // Segfaults here, was it already freed? } free(cmd->argv); free(cmd); } Edit 1: Also, I realized I need to stick program back in there as cmd-argv[0] Edit 2: Added call to calloc Edit 3: Edit mem management with tips from Alok Edit 4: More tips from alok Edit 5: Almost working.. the app segfaults when freeing the command struct Finally: Seems like I was missing the terminating NULL, so adding the line: cmd->argv[g.gl_pathc + g.gl_offs] = 0; seemed to make it work.

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  • mem-leak freeing g_strdup

    - by Mike
    I'm trying to free g_strdup but I'm not sure what I'm doing wrong. Using valgrind --tool=memcheck --leak-check=yes ./a.out I keep getting: ==4506== 40 bytes in 10 blocks are definitely lost in loss record 2 of 9 ==4506== at 0x4024C1C: malloc (vg_replace_malloc.c:195) ==4506== by 0x40782E3: g_malloc (in /lib/libglib-2.0.so.0.2200.3) ==4506== by 0x4090CA8: g_strdup (in /lib/libglib-2.0.so.0.2200.3) ==4506== by 0x8048722: add_inv (dup.c:26) ==4506== by 0x80487E6: main (dup.c:47) ==4506== 504 bytes in 1 blocks are possibly lost in loss record 4 of 9 ==4506== at 0x4023E2E: memalign (vg_replace_malloc.c:532) ==4506== by 0x4023E8B: posix_memalign (vg_replace_malloc.c:660) ==4506== by 0x408D61D: ??? (in /lib/libglib-2.0.so.0.2200.3) ==4506== by 0x408E5AC: g_slice_alloc (in /lib/libglib-2.0.so.0.2200.3) ==4506== by 0x4061628: g_hash_table_new_full (in /lib/libglib-2.0.so.0.2200.3) ==4506== by 0x40616C7: g_hash_table_new (in /lib/libglib-2.0.so.0.2200.3) ==4506== by 0x8048795: main (dup.c:42) I've tried different ways to freed but no success so far. I'll appreciate any help. Thanks BTW: It compiles and runs fine. #include <stdio.h> #include <string.h> #include <stdlib.h> #include <glib.h> #include <stdint.h> struct s { char *data; }; static GHashTable *hashtable1; static GHashTable *hashtable2; static void add_inv(GHashTable *table, const char *key) { gpointer old_value, old_key; gint value; if(g_hash_table_lookup_extended(table,key, &old_key, &old_value)){ value = GPOINTER_TO_INT(old_value); value = value + 2; /*g_free (old_key);*/ } else { value = 5; } g_hash_table_replace(table, g_strdup(key), GINT_TO_POINTER(value)); } static void print_hash_kv (gpointer key, gpointer value, gpointer user_data){ gchar *k = (gchar *) key; gchar *h = (gchar *) value; printf("%s: %d \n",k, h); } int main(int argc, char *argv[]){ struct s t; t.data = "bar"; int i,j; hashtable1 = g_hash_table_new(g_str_hash, g_str_equal); hashtable2 = g_hash_table_new(g_str_hash, g_str_equal); for(i=0;i<10;i++){ add_inv(hashtable1, t.data); add_inv(hashtable2, t.data); } /*free(t.data);*/ /*free(t.data);*/ g_hash_table_foreach (hashtable1, print_hash_kv, NULL); g_hash_table_foreach (hashtable2, print_hash_kv, NULL); g_hash_table_destroy(hashtable1); g_hash_table_destroy(hashtable2); return 0; }

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  • SaaS practical basics and projects

    - by Medardas
    So i need some directions. I want to understand Cloud Software as a Service(SaaS) practical initialization. The thing is I want to create a simple cloud service which would let me run programs on this cloud from remote machine. As I understand, I need some kind of specific backbone project to start this system, similar like OpenStack or Apache Cloud for Infostructure as a Service. Of course it may be that I understand it completely wrong and even if there is such project, it is not open source, free. I could also comprehend SaaS building on IaaS, but the thing is, I can't find any practical information at all. Could Somebody indulge me if there is any kind of free licence SaaS project or recommend a related articles or explain everything in a nut case with atleast vague direction.

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  • Best cheap GUI for converting to f4v

    - by Ben
    Hi, I need to give one client the ability to convert some videos to f4v h264 before loading it up to an AIR app. I normally doing with the Adobe Media Encoder CS4 but that only ships with adobe products (you can't download it as a free standalone app - which, start rant is odd, you'd think they would push the format - Microsoft's competing expresssion encoder is free end rant) Anyway, I need to get a (hopefully not too expensive, but willing to pay for it) good 3rd part app that can take any video and convert it to an f4v. Can you suggest any? Everything i've found is horrible or jammed with ads and crap. What would you use? Any suggestion? (please don't just say ffmpeg - I know it can do it but we need to good simple GUI) Thanks!

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  • What Web design tool would make a good CityDesk replacement?

    - by Joshua Fox
    I am looking for a tool for building static template-based web sites, your typical brochure-ware for a non-profit or a personal site. I have used CityDesk, but that is out-of-date, unsupported, and has certain problems. Of course there are lots of tools out there, but I cannot find anything similar to CityDesk: WYSIWYG as well as HTML coding a templating system not overdesigned like, say, Dreamweaver built for developers who understand HTML/JS/CSS but easier to use than hand-coding of PHP, Ruby, or other templates in a text editor supporting the editing of pages by non-developers preferably free I'd also like it to be CSS-aware; and to have lots of free templates available. Or alternatively, static template-based sites are often developed nowadays on the Web using a CMS like Django; is that the way to go? Edit: Namo, DreamWeaver, NetObjects Fusion, Coffee Cup, Evrsoft First Page, and Microsoft Expression might be candidates. I'll appreciate comments on these based on the criteria above.

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  • Looking for a lean WYSIWYG inline editor for CMS projects that includes an image upload feature?

    - by Roeland
    Hey guys, I am looking to find a lean WYSIWYG inline editor. The main required feature is image uploading. A simple way to upload an image to the server and use it in the content being editted. I have come across a whole bunch of editors but nothing I liked so far. I am looking for something open source and free. So far I have checked out TinyMCE which is free.. untill you need image uploading capabilities. Ckeditor looks great.. uses jquery.. but requires you to have your own server side script to upload images. They barely give any documentation on how to do this. There were a few others, but the bottom line was that I cant find anything that is simple with out of the box image uploading capabilities. Thanks for any advice you may give!

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  • VB.net: Custom ' TODO: List on an Interface

    - by Shiftbit
    How do I add my own todo and comments list to appear on Interfaces? I want it to pop up like IDisposable does: Public Class Foo : Implements IDisposable Private disposedValue As Boolean = False ' To detect redundant calls ' IDisposable Protected Overridable Sub Dispose(ByVal disposing As Boolean) If Not Me.disposedValue Then If disposing Then ' TODO: free other state (managed objects). End If ' TODO: free your own state (unmanaged objects). ' TODO: set large fields to null. End If Me.disposedValue = True End Sub #Region " IDisposable Support " ' This code added by Visual Basic to correctly implement the disposable pattern. Public Sub Dispose() Implements IDisposable.Dispose ' Do not change this code. Put cleanup code in Dispose(ByVal disposing As Boolean) above. Dispose(True) GC.SuppressFinalize(Me) End Sub #End Region End Class Whenever I enter my own comments and todo list they are never autogenerated like IDisposable Interface does. I would like my own Interfaces to preserve the comments so that I can share my Interfaces with in source documentation.

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  • hibernate search

    - by Odelya
    Hi! I am using Hibernate. I am looking for a free text engine. Before I investigate into it I need your experience. I have in my applications user, role and object table. Where a user is connected to one or more roles, and a role is connected to one or more objects. In my free text search, the user can reach only data that he is allowed to watch by object table. Can Hibernate search help me with it?

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  • Does malloc() allocate a contiguous block of memory?

    - by user66854
    I have a piece of code written by a very old school programmer :-) . it goes something like this typedef struct ts_request { ts_request_buffer_header_def header; char package[1]; } ts_request_def; ts_request_buffer_def* request_buffer = malloc(sizeof(ts_request_def) + (2 * 1024 * 1024)); the programmer basically is working on a buffer overflow concept. I know the code looks dodgy. so my questions are: Does malloc always allocate contiguous block of memory ?. because in this code if the blocks are not contiguous , the code will fail big time Doing free(request_buffer) , will it free all the bytes allocated by malloc i.e sizeof(ts_request_def) + (2 * 1024 * 1024), or only the bytes of the size of the structure sizeof(ts_request_def) Do you see any evident problems with this approach , i need to discuss this with my boss and would like to point out any loopholes with this approach

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