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  • Python / Django : emulating a multidimensional layer on a MySQL database

    - by Sébastien Piquemal
    Hi, I'm working on a Django project where I need to provide a lot of different visualizations on the same data (for example average of a value for each month, for each year / for a location, etc...). I have been using an OLAP database once in college, and I thought that it would fit my needs, but it appears that it is much too heavy for what I need. Actually the volume of data is not very big, so I don't need any optimization, just a way to present different visualizations of the same data without having to write 1000 times the same code. So, to recap, I need a python library: to emulate a multidimensional database (OLAP style would be nice because I think it is quite convenient : star structure, and everything) non-intrusive, because I can't modify anything on the existing MySQL database easy-to-use, because otherwise there's no point in replacing some overhead by another.

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  • mysql - filtering a list against keywords, both list and keywords > 20 million records

    - by threecheeseopera
    I have two tables, both having more than 20 million records; table1 is a list of terms, and table2 is a list of keywords that may or may not appear in those terms. I need to identify the terms that contain a keyword. My current strategy is: SELECT table1.term, table2.keyword FROM table1 INNER JOIN table2 ON table1.term LIKE CONCAT('%', table2.keyword, '%'); This is not working, it takes f o r e v e r. It's not the server (see notes). How might I rewrite this so that it runs in under a day? Notes: As for server optimization: both tables are myisam and have unique indexes on the matching fields; the myisam key buffer is greater than the sum of both index file sizes, and it is not even being fully taxed (key_blocks_unused is ... large); the server is a dual-xeon 2U beast with fast sas drives and 8G of ram, fine-tuned for the mysql workload.

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  • How secure is Microsoft 2007's encryption?

    - by ericl42
    I've read some various articles about Microsoft's encryption, and from what I gather, 2007 is secure using all default options due to it using AES, and 2000 and 2003 can be configured secure by changing the default algorithm to AES. I was wondering if anyone else has read any other articles or know of any specific vulnerabilities involved with how they implement the encryption. I would like to be able to tell users that they can use this to send semi sensitive documents as long as they use AES and a strong password. Thanks for the information.

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  • Reshape linux md raid5 that is already being reshaped?

    - by smammy
    I just converted my RAID1 array to a RAID5 array and added a third disk to it. I'd like to add a fourth disk without waiting fourteen hours for the first reshape to complete. I just did this: mdadm /dev/md0 --add /dev/sdf1 mdadm --grow /dev/md0 --raid-devices=3 --backup-file=/root/md0_n3.bak The entry in /proc/mdstat looks like this: md0 : active raid5 sdf1[2] sda1[0] sdb1[1] 976759936 blocks super 0.91 level 5, 64k chunk, algorithm 2 [3/3] [UUU] [>....................] reshape = 1.8% (18162944/976759936) finish=834.3min speed=19132K/sec Now I'd like to do this: mdadm /dev/md0 --add /dev/sdd1 mdadm --grow /dev/md0 --raid-devices=4 --backup-file=/root/md8_n4.bak Is this safe, or do I have to wait for the first reshape operation to complete? P.S.: I know I should have added both disks first, and then reshaped from 2 to 4 devices, but it's a little late for that.

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  • MATLAB Magical Mystery timing behavior

    - by Jacob Lyles
    I am experiencing some very odd timing behavior from a function I wrote. If I wrap my function inside another empty container function, it gets a 3x speedup. > tic; foo(args); toc time elapsed: ~140 seconds >tic; bar(args); toc time elapsed: ~35 seconds Here's the kicker - the definition of bar(): define bar(args) foo(args) end Is there some sort of optimization that gets triggered in MATLAB for nested function calls? Should I be adding a dummy function to every function that I write?

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  • Service haproxy error

    - by user128296
    I want to configure Haproxy for outgoing mail load balancing. my configuration file /etc/haproxy.cfg is. global maxconn 4096 # Total Max Connections. This is dependent on ulimit daemon nbproc 4 # Number of processing cores. Dual Dual-core Opteron is 4 cores for example. defaults mode tcp listen smtp_proxy 199.83.95.71:25 mode tcp option tcplog balance roundrobin # Load Balancing algorithm ## Define your servers to balance server r23.lbsmtp.org 74.117.x.x:25 weight 1 maxconn 512 check server r15.lbsmtp.org 199.71.x.x:25 weight 1 maxconn 512 check And when i start service haproxy i get this error. Starting HAproxy: [ALERT] 244/172148 (7354) : cannot bind socket for proxy smtp_proxy. Aborting. Please tell me where i am doing mistake.help will appreciated.

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  • What data type should I use for my texture coordinates in OpenGL ES?

    - by Matthew Chen
    I notice that the default data type for texture coordinates in the OpenGL docs is GLfloat, but much of the sample code I see written by experienced iphone developers uses GLshort or GLbyte. Is this an optimization? GLfloat vertices[] = { // Upper left x1, y2, // Lower left x1, y1, // Lower right x2, y1, // Upper right x2, y2, }; glTexCoordPointer(2, GL_FLOAT, 0, iconSTs); vs. GLbyte vertices[] = { // Upper left x1, y2, // Lower left x1, y1, // Lower right x2, y1, // Upper right x2, y2, }; glTexCoordPointer(2, GL_BYTE, 0, iconSTs);

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  • Roguelike FOV problem

    - by Manderin87
    I am working on a college compsci project and I would like some help with a field of view algorithm. I works mostly, but in some situations the algorithm sees through walls and hilights walls the player should not be able to see. void cMap::los(int x0, int y0, int radius) { //Does line of sight from any particular tile for(int x = 0; x < m_Height; x++) { for(int y = 0; y < m_Width; y++) { getTile(x,y)->setVisible(false); } } double xdif = 0; double ydif = 0; bool visible = false; float dist = 0; for (int x = MAX(x0 - radius,0); x < MIN(x0 + radius, m_Height); x++) { //Loops through x values within view radius for (int y = MAX(y0 - radius,0); y < MIN(y0 + radius, m_Width); y++) { //Loops through y values within view radius xdif = pow( (double) x - x0, 2); ydif = pow( (double) y - y0, 2); dist = (float) sqrt(xdif + ydif); //Gets the distance between the two points if (dist <= radius) { //If the tile is within view distance, visible = line(x0, y0, x, y); //check if it can be seen. if (visible) { //If it can be seen, getTile(x,y)->setVisible(true); //Mark that tile as viewable } } } } } bool cMap::line(int x0,int y0,int x1,int y1) { bool steep = abs(y1-y0) > abs(x1-x0); if (steep) { swap(x0, y0); swap(x1, y1); } if (x0 > x1) { swap(x0,x1); swap(y0,y1); } int deltax = x1-x0; int deltay = abs(y1-y0); int error = deltax/2; int ystep; int y = y0; if (y0 < y1) ystep = 1; else ystep = -1; for (int x = x0; x < x1; x++) { if ( steep && getTile(y,x)->isBlocked()) { getTile(y,x)->setVisible(true); getTile(y,x)->setDiscovered(true); return false; } else if (!steep && getTile(x,y)->isBlocked()) { getTile(x,y)->setVisible(true); getTile(x,y)->setDiscovered(true); return false; } error -= deltay; if (error < 0) { y = y + ystep; error = error + deltax; } } return true; } If anyone could help me make the first blocked tiles visible but stops the rest, I would appreciate it. thanks, Manderin87

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  • What is a flexible, hybrid python collection object?

    - by Naveen
    As a way to get used to python, I am trying to translate some of my code to python from Autohotkey_L. I am immediately running into tons of choices for collection objects. Can you help me figure out a built in type or a 3rd party contributed type that has as much as possible, the functionality of the AutoHotkey_L object type and its methods. AutoHotkey_L Objects have features of a python dict, list, and a class instance. I understand that there are tradeoffs for space and speed, but I am just interested in functionality rather than optimization issues.

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  • Strange performance behaviour for 64 bit modulo operation

    - by codymanix
    The last three of these method calls take approx. double the time than the first four. The only difference is that their arguments doesn't fit in integer anymore. But should this matter? The parameter is declared to be long, so it should use long for calculation anyway. Does the modulo operation use another algorithm for numbersmaxint? I am using amd athlon64 3200+, winxp sp3 and vs2008. Stopwatch sw = new Stopwatch(); TestLong(sw, int.MaxValue - 3l); TestLong(sw, int.MaxValue - 2l); TestLong(sw, int.MaxValue - 1l); TestLong(sw, int.MaxValue); TestLong(sw, int.MaxValue + 1l); TestLong(sw, int.MaxValue + 2l); TestLong(sw, int.MaxValue + 3l); Console.ReadLine(); static void TestLong(Stopwatch sw, long num) { long n = 0; sw.Reset(); sw.Start(); for (long i = 3; i < 20000000; i++) { n += num % i; } sw.Stop(); Console.WriteLine(sw.Elapsed); } EDIT: I now tried the same with C and the issue does not occur here, all modulo operations take the same time, in release and in debug mode with and without optimizations turned on: #include "stdafx.h" #include "time.h" #include "limits.h" static void TestLong(long long num) { long long n = 0; clock_t t = clock(); for (long long i = 3; i < 20000000LL*100; i++) { n += num % i; } printf("%d - %lld\n", clock()-t, n); } int main() { printf("%i %i %i %i\n\n", sizeof (int), sizeof(long), sizeof(long long), sizeof(void*)); TestLong(3); TestLong(10); TestLong(131); TestLong(INT_MAX - 1L); TestLong(UINT_MAX +1LL); TestLong(INT_MAX + 1LL); TestLong(LLONG_MAX-1LL); getchar(); return 0; } EDIT2: Thanks for the great suggestions. I found that both .net and c (in debug as well as in release mode) does't not use atomically cpu instructions to calculate the remainder but they call a function that does. In the c program I could get the name of it which is "_allrem". It also displayed full source comments for this file so I found the information that this algorithm special cases the 32bit divisors instead of dividends which was the case in the .net application. I also found out that the performance of the c program really is only affected by the value of the divisor but not the dividend. Another test showed that the performance of the remainder function in the .net program depends on both the dividend and divisor. BTW: Even simple additions of long long values are calculated by a consecutive add and adc instructions. So even if my processor calls itself 64bit, it really isn't :( EDIT3: I now ran the c app on a windows 7 x64 edition, compiled with visual studio 2010. The funny thing is, the performance behavior stays the same, although now (I checked the assembly source) true 64 bit instructions are used.

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  • C: Pointers to any type?

    - by dragme
    I hear that C isn't so type-safe and I think that I could use that as an advantage for my current project. I'm designing an interpreter with the goal for the VM to be extremely fast, much faster than Ruby and Python, for example. Now I know that premature optimization "is the root of all evil" but this is rather a conceptual problem. I have to use some sort of struct to represent all values in my language (from number over string to list and map) Would the following be possible? struct Value { ValueType type; void* value; } I would store the actual values elsewhere, e.g: a separate array for strings and integers, value* would then point to some member in this table. I would always know the type of the value via the type variable, so there wouldn't be any problems with type errors. Now: Is this even possible in terms of syntax and typing?

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  • fetch only first row from oracle - is it faster?

    - by john
    My main goal with this question is optimization and faster run time. After doing lot of processing in the Stored Proc I finally return a count like below: OPEN cv_1 FOR SELECT COUNT(*) num_of_members FROM HOUSEHOLD_MEMBER a, HOUSEHOLD b WHERE RTRIM(LTRIM(a.mbr_last_name)) LIKE v_MBR_LAST_NAME || '%' AND a.number = '01' AND a.code = v_CODE AND a.ssn_head = v_SSN_HEAD AND TO_CHAR( a.mbr_dob, 'MM/DD/YYYY') = v_DOB; But in my code that is calling the SP does not need the actual count. It just cares that count is greater than 1. Question: How can I change this to return just 1 or 0. 1 when count is 0 and 0 when count 1. Will it be faster to do this rather than returning the whole count?

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  • What Kind of Knowledge is Necessary For a Permon Who Does Not Have IT Background? [closed]

    - by skyflyer
    One of my colleagues joined our company, which by the way is a internet company, months ago as an on-line marketing specialist. He majored English in his college and has never deeply touched IT before. He says that to be a good on-line marketing specialist he needs to lean some basic IT skills in order to deliver superb work. According to him, things like Search Engine Optimization, monitoring competitors' web sites, design some functionality on web site and so on require IT entree-level knowledge. And he asks me what kind knowledge is helpful for him to do his job. I am stunted by his question. It is easy enough to answer, things like HTML, CSS, even Photo-shop are required in some job descriptions. Also, I believe some basic understanding of dynamic web site, static web site is helpful to him. On the other hand, as a techie I still feel my answer is awkward. What is your opinion on this? Always lot of thanks to you guys on SO.

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  • Browser loading strategy, <head>...<body>

    - by Bin Chen
    I am inspecting some interesting behaviors of browser, I don't know it's in standard or not. If I put everythin inside <head></head>, the browser will only begin to render the page after all the resouces in head is retrieved. So I am thinking that put as little as possible things into head is one of the important website optimization techniques, is it right? My question is: If I put script/css in body or other parts of the html, how can I know that script has been loaded successfully so that I will not be calling a undefined function?

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  • Python / Django : emulating a multidimensionnal layer on a mySql database

    - by Sébastien Piquemal
    Hi, I'm working on a Django project where I need to provide a lot of different visualizations on the same data (for example average of a value for each month, for each year / for a location, etc ...). I have been using OLAP database once in college, and I thought that it would fit my needs, but it appears that it is much to heavy for what I need. Actually the volume of data is not very big, so I don't need any optimization, just a way to present different visualizations of the same data without having to write 1000 times the same code. So let's recap : I need a python library : to emulate a multidimensional database (OLAP style would be nice because I think it is quite convenient : stat structure, and everything) non-intrusive, because I can't modify anything on the existing mysql database easy-to-use, because otherwise there's no point in replacing some overhead by another.

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  • SQL Query - 20mil records - Best practice to return information

    - by eqiz
    I have a SQL database that has the following table: Table: PhoneRecords ID(identity Seed) FirstName LastName PhoneNumber ZipCode Very simple straight forward table. This table has over 20million records. I am looking for the best way to do queries that pull out records based off area codes from the table. For instance here is an example query that I have done. SELECT phonenumber, firstname FROM [PhoneRecords] WHERE (phone LIKE '2012042%') OR (phone LIKE '2012046%') OR (phone LIKE '2012047%') OR (phone LIKE '2012083%') OR (phone LIKE '2012088%') OR (phone LIKE '2012841%') As you can see this is an ugly query, but it would get the job done (if I wasn't running into timeout issues) Can anyone tell me the best way for speed/optimization to do the above query to display the results? Currently that query above takes around 2 hours to complete on a 9gb 1600mhz ram, i7 930 quadcore OC'd 4.01ghz. I obviously have the computer power required to do such a query, but still takes too long for queries.

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  • linux/shell: change a file's modify timestamp relatively?

    - by index
    My Canon camera produces files like IMG_1234.JPG and MVI_1234.AVI. It also timestamps those files. Unfortunately during a trip to another timezone several cameras were used, one of which did not have the correct time zone set - meta data mess.. Now I would like to correct this (not EXIF, the file's "modify" timestamp on disk). Proposed algorithm: 1 read file's modify date 2 add delta, i.e. hhmmss (preferred: change timezone) 3 write new timestamp Unless someone knows a tool or a combination of tools that do the trick directly, maybe one could simplify the calculation using epoch time (seconds since ..) and whip up a shell script. Any help appreciated!

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  • Is it possible to give a python dict an initial capacity (and is it usefull)

    - by Peter Smit
    I am filling a python dict with around 10,000,000 items. My understanding of dict (or hashtables) is that when too much elements get in them, the need to resize, an operation that cost quite some time. Is there a way to say to a python dict that you will be storing at least n items in it, so that it can allocate memory from the start? Or will this optimization not do any good to my running speed? (And no, I have not checked that the slowness of my small script is because of this, I actually wouldn't now how to do that. This is however something I would do in Java, set the initial capacity of the HashSet right)

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  • weighted RNG speed problem in C++

    - by supert
    I have a (fast) bit of C++ code that samples cards from a 52 card deck: void sample_allcards(int table[5], int holes[], int players) { int temp[5 + 2 * players]; bool try_again; int c, n, i; for (i = 0; i < 5 + 2 * players; i++) { try_again = true; while (try_again == true) { try_again = false; c = fast_rand52(); // reject collisions for (n = 0; n < i + 1; n++) { try_again = (temp[n] == c) || try_again; } temp[i] = c; } } copy_cards(table, temp, 5); copy_cards(holes, temp + 5, 2 * players); } I am implementing code to sample the hole cards according to a known distribution (stored as a 2d table). My code for this looks like: void sample_allcards_weighted(double weights[][HOLE_CARDS], int table[5], int holes[], int players) { // weights are distribution over hole cards int temp[5 + 2 * players]; int n, i; // table cards for (i = 0; i < 5; i++) { bool try_again = true; while (try_again == true) { try_again = false; int c = fast_rand52(); // reject collisions for (n = 0; n < i + 1; n++) { try_again = (temp[n] == c) || try_again; } temp[i] = c; } } for (int player = 0; player < players; player++) { // hole cards according to distribution i = 5 + 2 * player; bool try_again = true; while (try_again == true) { try_again = false; // weighted-sample c1 and c2 at once double w[1326]; memcpy(w, weights[player], sizeof(w)); // h is a number < 1325 int h = weighted_randi(w, HOLE_CARDS); // i2h uses h and sets temp[i] to the 2 cards implied by h i2h(&temp[i], h); // reject collisions for (n = 0; n < i; n++) { try_again = (temp[n] == temp[i]) || (temp[n] == temp[i+1]) || try_again; } } } copy_cards(table, temp, 5); copy_cards(holes, temp + 5, 2 * players); } My problem? The weighted sampling algorithm is a factor of 10 slower. Speed is very important for my application. Is there a way to improve the speed of my algorithm to something more reasonable? Am I doing something wrong in my implementation? Thanks.

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  • MySQL: Get unique values across multiple columns in alphabetical order

    - by RuCh
    Hey everyone, If my table looks like this: id | colA | colB | colC =========================== 1 | red | blue | yellow 2 | orange | red | red 3 | orange | blue | cyan What SELECT query do I run such that the results returned are: blue, cyan, orange, red, yellow Basically, I want to extract a collective list of distinct values across multiple columns and return them in alphabetical order. I am not concerned with performance optimization, because the results are being parsed to an XML file that will serve as a cache (database is hardly updated). So even a dirty solution would be fine. Thanks for any help!

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  • Detect template presence at compilation time

    - by doublep
    GCC up to 4.5 doesn't have standard C++0x type trait template has_nothrow_move_constructor. I could use it in my package for optimization, but I don't want to rule out one of the common compilers and don't want to overload configuration with symbols like HAVE_STD_HAS_NOTHROW_MOVE_CONSTRUCTOR. Is it somehow possible to use that template if present and just fall back to copying if not present without using any predefined configuration symbols? I also don't want to depend on Boost, since my library is small and doesn't need Boost for any other reasons. In pseudocode, I need something like: template <typename type> struct has_nothrow_move_constructor_robust : public integral_constant <bool, /* if possible */ has_nothrow_move_constructor <type>::value /* otherwise */ false> { }; Since move constructors are only for C++0x anyway, I don't mind using other C++0x features for the above definition, if at all possible.

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  • Has Object in VB 2010 received the same optimalization as dynamic in C# 4.0?

    - by Abel
    Some people have argued that the C# 4.0 feature introduced with the dynamic keyword is the same as the "everything is an Object" feature of VB. However, any call on a dynamic variable will be translated into a delegate once and from then on, the delegate will be called. In VB, when using Object, no caching is applied and each call on a non-typed method involves a whole lot of under-the-hood reflection, sometimes totaling a whopping 400-fold performance penalty. Have the dynamic type delegate-optimization and caching also been added to the VB untyped method calls, or is VB's untyped Object still so slow?

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  • How to Software Service Industry get their Client from or where do they look for their Clients ?

    - by Rachel
    This question is inclined more towards Business Side of Software Industry, I am sure that we have two types in Software Industry as with any other Industry, i.e, Service side and Product Side. Basically for Product based company, we are looking more into product features and to see if market if mature or not for particular product but as far as Service Based company goes (may be it can be big giants like Infosys, TCS or Sapient or some midsize or small companies which provide services like:Web Design,Website Design,Corporate Identity,Logo Design,Flash Design,Web Applications,Enterprise Portal,Rich Internet Applications,Business Applications,Technology Consulting,Ecommerce,Online Store Creations,Custom Shopping Carts,Ecommerce Hosting,Website Marketing,Organic SEO,Pay-Per-Click,Social Media Optimization,Mobile,Mobile Website and Mobile Applications) where do they look for Client and how do they manage to get one ? So my basic question is Where do Service Based Companies Look for Client or get their Clients Form ?

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  • new image makes http request even though cached?

    - by joshs
    I have a javascript slide show that creates the next slide dynamically and then moves it into view. Since the images are actually sprites, the src is transparent.png and the actual image is mapped via background:url(.. in css. Everytime (well, most of the time) the script creates a new Element, Firefox makes an http request for transparent.png. I have a far-future expires header, and Firefox is respecting all other files' expiries. Is there a way to avoid these unnecessary requests. Even though the server is returning 304 unmodified responses, it would be nice if Firefox would respect the expiries on dynamically created images. I suspect that if I injected a simple string instead of using new Element, this might solve the problem, but I use some methods on Prototypes extended Element object, so I would like to avoid a bunch of html strings in my js file. This is a nit-picky question, but I'm working on front-end optimization now, so I thought I would address it. Thanks.

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  • Incremental Compilation in Eclipse. ASTNode-s and SVN versioning

    - by Alex
    Hi there, I am building up some statistics after analyzing the source code in eclipse. But the overall process is too slow because i rebuild my model every time from scratch after each compilation. I am looking for a way to get only the changed parts of the code (as ASTNodes) and to rebuild just that part of my model. I suppose that even the changed compilation units and not the exact code elements would be enough after the user compiles and still would be a nice optimization. I am sure eclipse is capable of knowing what code elements are changed (and even to know their semantics), because when I use the subclipse plugin my changes are ordered by a code element (an import, a method, a variable declaration, etc). Well.. at least that plugin is capable of knowing that info. Thanks in advance

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