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Time complexity to fill hash table (homework)?

- by Heathcliff

This is a homework question, but I think there's something missing from it. It asks: Provide a sequence of m keys to fill a hash table implemented with linear probing, such that the time to fill it is minimum. And then Provide another sequence of m keys, but such that the time fill it is maximum. Repeat these two questions if the hash table implements quadratic probing I can only assume that the hash table has size m, both because it's the only number given and because we have been using that letter to address a hash table size before when describing the load factor. But I can't think of any sequence to do the first without knowing the hash function that hashes the sequence into the table. If it is a bad hash function, such that, for instance, it hashes every entry to the same index, then both the minimum and maximum time to fill it will take O(n) time, regardless of what the sequence looks like. And in the average case, where I assume the hash function is OK, how am I suppossed to know how long it will take for that hash function to fill the table? Aren't these questions linked to the hash function stronger than they are to the sequence that is hashed? As for the second question, I can assume that, regardless of the hash function, a sequence of size m with the same key repeated m-times will provide the maximum time, because it will cause linear probing from the second entry on. I think that will take O(n) time. Is that correct? Thanks

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How can I read the value of a radio button in JavaScript?

- by Corey

<html> <head> <title>Tip Calculator</title> <script type="text/javascript"></script> </head> <body> <h1 style="text-align:center">Tip Calculator</h1> <form id="f1" name="f1"> Average Service: 15% <input type="radio" id="tipPercent" name="tipPercent" value="15" /> <br /> Excellent Service: 20% <input type="radio" id="tipPercent" name="tipPercent" value="20" /> <br /><br /> <label>Check Amount</label> <input type="text" id="check" size="10" /> <input type="button" onclick="calculateBill()" value="Calculate" /> </form> <br /> Total Bill: <p id="bill"></p> </body> </html> I try to get the value selected with document.getElementById("tipPercent").value, but it always returns the value 15.

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Using `<List>` when dealing with pointers in C#.

- by Gorchestopher H

How can I add an item to a list if that item is essentially a pointer and avoid changing every item in my list to the newest instance of that item? Here's what I mean: I am doing image processing, and there is a chance that I will need to deal with images that come in faster than I can process (for a short period of time). After this "burst" of images I will rely on the fact that I can process faster than the average image rate, and will "catch-up" eventually. So, what I want to do is put my images into a <List> when I acquire them, then if my processing thread isn't busy, I can take an image from that list and hand it over. My issue is that I am worried that since I am adding the image "Image1" to the list, then filling "Image1" with a new image (during the next image acquisition) I will be replacing the image stored in the list with the new image as well (as the image variable is actually just a pointer). So, my code looks a little like this: while (!exitcondition) { if(ImageAvailabe()) { Image1 = AcquireImage(); ImgList.Add(Image1); } if(ImgList.Count 0) { ProcessEngine.NewImage(ImgList[0]); ImgList.RemoveAt(0); } } Given the above, how can I ensure that: - I don't replace all items in the list every time Image1 is modified. - I don't need to pre-declare a number of images in order to do this kind of processing. - I don't create a memory devouring monster. Any advice is greatly appreciated.

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multi-shop orders table and sequential order numbers based on shop

- by imanc

Hey, I am looking at building a shop solution that needs to be scalable. Currently it retrieves 1-2000 orders on average per day across multiple country based shops (e.g. uk, us, de, dk, es etc.) but this order could be 10x this amount in two years. I am looking at either using separate country-shop databases to store the orders tables, or looking to combine all into one order table. If all orders exist in one table with a global ID (auto num) and country ID (e.g uk,de,dk etc.), each countries orders would also need to have sequential ordering. So in essence, we'd have to have a global ID and a country order ID, with the country order ID being sequential for countries only, e.g. global ID = 1000, country = UK, country order ID = 1000 global ID = 1001, country = DE, country order ID = 1000 global ID = 1002, country = DE, country order ID = 1001 global ID = 1003, country = DE, country order ID = 1002 global ID = 1004, country = UK, country order ID = 1001 THe global ID would be DB generated and not something I would need to worry about. But I am thinking that I'd have to do a query to get the current country order based ID+1 to find the next sequential number. Two things concern me about this: 1) query times when the table has potentially millions of rows of data and I'm doing a read before a write, 2) the potential for ID number clashes due to simultaneous writes/reads. With a MyISAM table the entire table could be locked whilst the last country order + 1 is retrieved, to prevent ID number clashes. I am wondering if anyone knows of a more elegant solution? Cheers, imanc

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python tkinter gui

- by Lewis Townsend

I'm wanting to make a small python program for yearly temperatures. I can get nearly everything working in the standard console but I'm wanting to implement it into a GUI. The program opens a csv file reads it into lists, works out the average, and min & max temps. Then on closing the application will save a summary to a new text file. I am wanting the default start up screen to show All Years. When a button is clicked it just shows that year's data. Here is a what I want it to look like. Pretty simple layout with just the 5 buttons and the out puts for each. I can make up the buttons for the top fine with: Code: class App: def __init__(self, master): frame = Frame(master) frame.pack() self.hi_there = Button(frame, text="All Years", command=self.All) self.hi_there.pack(side=LEFT) self.hi_there = Button(frame, text="2011", command=self.Y1) self.hi_there.pack(side=LEFT) self.hi_there = Button(frame, text="2012", command=self.Y2) self.hi_there.pack(side=LEFT) self.hi_there = Button(frame, text="2013", command=self.Y3) self.hi_there.pack(side=LEFT) self.hi_there = Button(frame, text="Save & Exit", command=self.Exit) self.hi_there.pack(side=LEFT) I'm not sure as to how to make the other elements, such as the title & table. I was going to post the code of the small program but decided not to. Once I have the structure/framework I think I can populate the fields & I might learn better this way. Using Python 2.7.3

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What could cause these Apache crash errors ?

- by jacobanderssen

Hello guys. I had a server crash several days ago. I use Cacti to keep stats: at the time when the server crashed, a huge spike from Load 1 to Load 200 occurred, with over 800 processes in the run queue ( from 300 average). Upon checking /var/log/httpd I notice this: * glibc detected /usr/sbin/httpd: double free or corruption (out): 0x00002b8f3142c2f0 ** Followed by alot of these: [Sat Mar 13 19:20:20 2010] [warn] child process 3090 still did not exit, sending a SIGTERM [Sat Mar 13 19:20:20 2010] [warn] child process 3091 still did not exit, sending a SIGTERM Followed by this: ======= Backtrace: ========= /lib64/libc.so.6[0x2b8f1463c2ef] /lib64/libc.so.6(cfree+0x4b)[0x2b8f1463c73b] /usr/lib64/libapr-1.so.0(apr_pool_destroy+0x131)[0x2b8f13f98821] /usr/sbin/httpd[0x2b8f126df47e] /usr/sbin/httpd[0x2b8f126df4ab] /lib64/libpthread.so.0[0x2b8f141b87c0] /etc/httpd/modules/mod_file_cache.so[0x2b8f1cdf00fb] ======= Memory map: ======== And finally a lot of these: [Sat Mar 13 19:20:27 2010] [error] could not make child process 733 exit, attempting to continue anyway [Sat Mar 13 19:20:27 2010] [error] could not make child process 24560 exit, attempting to continue anyway [Sat Mar 13 19:20:27 2010] [error] could not make child process 31384 exit, attempting to continue anyway I am also noticing one or two lines like this: [Mon Mar 15 01:17:26 2010] [notice] child pid 20765 exit signal Segmentation fault (11) Please help me shed some light on this. Thanks !

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Why do C# containers and GUI classes use int and not uint for size related members ?

- by smerlin

I usually program in C++, but for school i have to do a project in C#. So i went ahead and coded like i was used to in C++, but was surprised when the compiler complained about code like the following: const uint size = 10; ArrayList myarray = new ArrayList(size); //Arg 1: cannot convert from 'uint' to 'int Ok they expect int as argument type, but why ? I would feel much more comfortable with uint as argument type, because uint fits much better in this case. Why do they use int as argument type pretty much everywhere in the .NET library even if though for many cases negative numbers dont make any sense (since no container nor gui element can have a negative size). If the reason that they used int is, that they didnt expect that the average user cares about signedness, why didnt they add overloads for uint additonally ? Is this just MS not caring about sign correctness or are there cases where negative values make some sense/ carry some information (error code ????) for container/gui widget/... sizes ?

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Loading/Displaying large amount of data on webpage.

- by jb

I have a webpage which contains a table for displaying a large amount of data (on average from 2,000 to 10,000 rows). This page takes a long time to load/render. Which is understandable. The problem is, while the page is loading the PCs memory usage skyrockets (500mb on my test system is in use by iexplorer) and the whole PC grinds to a halt until it has finished, which can take a minute or two. IE hangs until it is complete, switching to another running program is the same. I need to fix this - and ideally i want to accomplish 2 things: 1) Load individual parts of the page seperately. So the page can render initially without the large data table. A loading div will be placed there until it is ready. 2) Dont use up so much memory or local resources while rendering - so at least they can use a different tab/application at the same time. How would I go about doing both or either of these? I'm an applications programmer by trade so i am still a little fizzy on the things I can do in a web environment. Cheers all.

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Who's setting TCP window size down to 0, Indy or Windows?

- by François

We have an application server which have been observed sending headers with TCP window size 0 at times when the network had congestion (at a client's site). We would like to know if it is Indy or the underlying Windows layer that is responsible for adjusting the TCP window size down from the nominal 64K in adaptation to the available throughput. And we would be able to act upon it becoming 0 (nothing gets send, users wait = no good). So, any info, link, pointer to Indy code are welcome... Disclaimer: I'm not a network specialist. Please keep the answer understandable for the average me ;-) Note: it's Indy9/D2007 on Windows Server 2003 SP2. More gory details: The TCP zero window cases happen on the middle tier talking to the DB server. It happens at the same moments when end users complain of slowdowns in the client application (that's what triggered the network investigation). 2 major Network issues causing bottlenecks have been identified. The TCP zero window happened when there was network congestion, but may or may not be caused by it. We want to know when that happen and have a way to do something (logging at least) in our code. So where to hook (in Indy?) to know when that condition occurs?

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Non standard interaction among two tables to avoid very large merge

- by riko

Suppose I have two tables A and B. Table A has a multi-level index (a, b) and one column (ts). b determines univocally ts. A = pd.DataFrame( [('a', 'x', 4), ('a', 'y', 6), ('a', 'z', 5), ('b', 'x', 4), ('b', 'z', 5), ('c', 'y', 6)], columns=['a', 'b', 'ts']).set_index(['a', 'b']) AA = A.reset_index() Table B is another one-column (ts) table with non-unique index (a). The ts's are sorted "inside" each group, i.e., B.ix[x] is sorted for each x. Moreover, there is always a value in B.ix[x] that is greater than or equal to the values in A. B = pd.DataFrame( dict(a=list('aaaaabbcccccc'), ts=[1, 2, 4, 5, 7, 7, 8, 1, 2, 4, 5, 8, 9])).set_index('a') The semantics in this is that B contains observations of occurrences of an event of type indicated by the index. I would like to find from B the timestamp of the first occurrence of each event type after the timestamp specified in A for each value of b. In other words, I would like to get a table with the same shape of A, that instead of ts contains the "minimum value occurring after ts" as specified by table B. So, my goal would be: C: ('a', 'x') 4 ('a', 'y') 7 ('a', 'z') 5 ('b', 'x') 7 ('b', 'z') 7 ('c', 'y') 8 I have some working code, but is terribly slow. C = AA.apply(lambda row: ( row[0], row[1], B.ix[row[0]].irow(np.searchsorted(B.ts[row[0]], row[2]))), axis=1).set_index(['a', 'b']) Profiling shows the culprit is obviously B.ix[row[0]].irow(np.searchsorted(B.ts[row[0]], row[2]))). However, standard solutions using merge/join would take too much RAM in the long run. Consider that now I have 1000 a's, assume constant the average number of b's per a (probably 100-200), and consider that the number of observations per a is probably in the order of 300. In production I will have 1000 more a's. 1,000,000 x 200 x 300 = 60,000,000,000 rows may be a bit too much to keep in RAM, especially considering that the data I need is perfectly described by a C like the one I discussed above. How would I improve the performance?

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Out of memory when creating a lot of objects C#

- by Bas

I'm processing 1 million records in my application, which I retrieve from a MySQL database. To do so I'm using Linq to get the records and use .Skip() and .Take() to process 250 records at a time. For each retrieved record I need to create 0 to 4 Items, which I then add to the database. So the average amount of total Items that has to be created is around 2 million. while (objects.Count != 0) { using (dataContext = new LinqToSqlContext(new DataContext())) { foreach (Object objectRecord in objects) { // Create a list of 0 - 4 Random Items and add each Item to the Object for (int i = 0; i < Random.Next(0, 4); i++) { Item item = new Item(); item.Id = Guid.NewGuid(); item.Object = objectRecord.Id; item.Created = DateTime.Now; item.Changed = DateTime.Now; dataContext.InsertOnSubmit(item); } } dataContext.SubmitChanges(); } amountToSkip += 250; objects = objectCollection.Skip(amountToSkip).Take(250).ToList(); } Now the problem arises when creating the Items. When running the application (and not even using dataContext) the memory increases consistently. It's like the items are never getting disposed. Does anyone notice what I'm doing wrong? Thanks in advance!

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algorithm - How to sort a 0/1 array with 2n/3 comparisons?

- by Jackson Tale

In Algorithm Design Manual, there is such an excise 4-26 Consider the problem of sorting a sequence of n 0’s and 1’s using comparisons. For each comparison of two values x and y, the algorithm learns which of x < y, x = y, or x y holds. (a) Give an algorithm to sort in n - 1 comparisons in the worst case. Show that your algorithm is optimal. (b) Give an algorithm to sort in 2n/3 comparisons in the average case (assuming each of the n inputs is 0 or 1 with equal probability). Show that your algorithm is optimal. For (a), I think it is fairly easy. I can choose a[n-1] as pivot, then do something like in quicksort partition, scan 0 to n - 2, find the middle point where left side is all 0 and right side is all 1, this take n - 1 comparisons. But for (b), I can't get a clue. It says "each of the n inputs is 0 or 1 with equal probability", so I guess I can assume the numbers of 0 and 1 equal? But how can I get a result which is related to 1/3? divide the whole array into 3 groups? Thanks

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Largest triangle from a set of points

- by Faken

I have a set of random points from which i want to find the largest triangle by area who's verticies are each on one of those points. So far I have figured out that the largest triangle's verticies will only lie on the outside points of the cloud of points (or the convex hull) so i have programmed a function to do just that (using Graham scan in nlogn time). However that's where I'm stuck. The only way I can figure out how to find the largest triangle from these points is to use brute force at n^3 time which is still acceptable in an average case as the convex hull algorithm usually kicks out the vast majority of points. However in a worst case scenario where points are on a circle, this method would fail miserably. Dose anyone know an algorithm to do this more efficiently? Note: I know that CGAL has this algorithm there but they do not go into any details on how its done. I don't want to use libraries, i want to learn this and program it myself (and also allow me to tweak it to exactly the way i want it to operate, just like the graham scan in which other implementations pick up collinear points that i don't want).

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Is There a Better Way to Feed Different Parameters into Functions with If-Statements?

- by FlowofSoul

I've been teaching myself Python for a little while now, and I've never programmed before. I just wrote a basic backup program that writes out the progress of each individual file while it is copying. I wrote a function that determines buffer size so that smaller files are copied with a smaller buffer, and bigger files are copied with a bigger buffer. The way I have the code set up now doesn't seem very efficient, as there is an if loop that then leads to another if loops, creating four options, and they all just call the same function with different parameters. import os import sys def smartcopy(filestocopy, dest_path, show_progress = False): """Determines what buffer size to use with copy() Setting show_progress to True calls back display_progress()""" #filestocopy is a list of dictionaries for the files needed to be copied #dictionaries are used as the fullpath, st_mtime, and size are needed if len(filestocopy.keys()) == 0: return None #Determines average file size for which buffer to use average_size = 0 for key in filestocopy.keys(): average_size += int(filestocopy[key]['size']) average_size = average_size/len(filestocopy.keys()) #Smaller buffer for smaller files if average_size < 1024*10000: #Buffer sizes determined by informal tests on my laptop if show_progress: for key in filestocopy.keys(): #dest_path+key is the destination path, as the key is the relative path #and the dest_path is the top level folder copy(filestocopy[key]['fullpath'], dest_path+key, callback = lambda pos, total: display_progress(pos, total, key)) else: for key in filestocopy.keys(): copy(filestocopy[key]['fullpath'], dest_path+key, callback = None) #Bigger buffer for bigger files else: if show_progress: for key in filestocopy.keys(): copy(filestocopy[key]['fullpath'], dest_path+key, 1024*2600, callback = lambda pos, total: display_progress(pos, total, key)) else: for key in filestocopy.keys(): copy(filestocopy[key]['fullpath'], dest_path+key, 1024*2600) def display_progress(pos, total, filename): percent = round(float(pos)/float(total)*100,2) if percent <= 100: sys.stdout.write(filename + ' - ' + str(percent)+'% \r') else: percent = 100 sys.stdout.write(filename + ' - Completed \n') Is there a better way to accomplish what I'm doing? Sorry if the code is commented poorly or hard to follow. I didn't want to ask someone to read through all 120 lines of my poorly written code, so I just isolated the two functions. Thanks for any help.

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Creating and appending a big DOM with javascript - most optimized way?

- by fenderplayer

I use the following code to append a big dom on a mobile browser (webkit): 1. while(someIndex--) // someIndex ranges from 10 to possibly 1000 2. { 3. var html01 = ['<div class="test">', someVal,'</div>', 4. '<div><p>', someTxt.txt1, someTxt.txt2, '</p></div>', 5. // lots of html snippets interspersed with variables 6. // on average ~40 to 50 elements in this array 7. ].join(''); 8. var fragment = document.createDocumentFragment(), 9. div = fragment.appendChild(document.createElement('div')); 10. div.appendChild(jQuery(html01)[0]); 11. jQuery('#screen1').append(fragment); 12. } //end while loop 13. // similarly i create 'html02' till 'html15' to append in other screen divs Is there a better or faster way to do the above? Do you see any problems with the code? I am a little worried about line 10 where i wrap in jquery and then take it out.

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How to improve Visual C++ compilation times?

- by dtrosset

I am compiling 2 C++ projects in a buildbot, on each commit. Both are around 1000 files, one is 100 kloc, the other 170 kloc. Compilation times are very different from gcc (4.4) to Visual C++ (2008). Visual C++ compilations for one project take in the 20 minutes. They cannot take advantage of the multiple cores because a project depend on the other. In the end, a full compilation of both projects in Debug and Release, in 32 and 64 bits takes more than 2 1/2 hours. gcc compilations for one project take in the 4 minutes. It can be parallelized on the 4 cores and takes around 1 min 10 secs. All 8 builds for 4 versions (Debug/Release, 32/64 bits) of the 2 projects are compiled in less than 10 minutes. What is happening with Visual C++ compilation times? They are basically 5 times slower. What is the average time that can be expected to compile a C++ kloc? Mine are 7 s/kloc with vc++ and 1.4 s/kloc with gcc. Can anything be done to speed-up compilation times on Visual C++?

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Undesired Output of Crontab Job Using CURL

- by Russell C.

I have written a perl script that runs as a daily crontab job that uploads files to Amazon S3 via CURL. I want the output of the cron job emailed to me which works fine but I don't want that email to include messages related to the CURL upload (only those message my script is outputting). Here are the CURL related messages I'm seeing in the daily email right now: % Total % Received % Xferd Average Speed Time Time Time Current Dload Upload Total Spent Left Speed 0 230M 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0 0 230M 0 0 0 544k 0 1519k 0:02:35 --:--:-- 0:02:35 1807k 0 230M 0 0 0 1744k 0 1286k 0:03:03 0:00:01 0:03:02 1342k 1 230M 0 0 1 2880k 0 1219k 0:03:13 0:00:02 0:03:11 1250k 1 230M 0 0 1 4016k 0 1198k 0:03:17 0:00:03 0:03:14 1218k 2 230M 0 0 2 5168k 0 1186k 0:03:19 0:00:04 0:03:15 1202k 2 230M 0 0 2 6336k 0 1181k 0:03:19 0:00:05 0:03:14 1157k 3 230M 0 0 3 7488k 0 1177k 0:03:20 0:00:06 0:03:14 1147k 3 230M 0 0 3 8592k 0 1167k 0:03:22 0:00:07 0:03:15 1142k 4 230M 0 0 4 9744k 0 1166k 0:03:22 0:00:08 0:03:14 1145k 4 230M 0 0 4 10.6M 0 1163k 0:03:23 0:00:09 0:03:14 1142k 5 230M 0 0 5 11.7M 0 1161k 0:03:23 0:00:10 0:03:13 1140k 5 230M 0 0 5 12.8M 0 1158k 0:03:23 0:00:11 0:03:12 1133k 6 230M 0 0 6 13.9M 0 1155k 0:03:24 0:00:12 0:03:12 1138k 6 230M 0 0 6 15.0M 0 1155k 0:03:24 0:00:13 0:03:11 1138k 7 230M 0 0 7 16.1M 0 1152k 0:03:25 0:00:14 0:03:11 1131k 7 230M 0 0 7 17.2M 0 1152k 0:03:25 0:00:15 0:03:10 1132k 7 230M 0 0 7 18.4M 0 1152k 0:03:24 0:00:16 0:03:08 1140k I am using a simple Perl system() call to invoke CURL. Does anyone know what command line argument I can supply CURL to turn off the reporting of the upload progress? Thanks in advance for your help!

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Out-of-memory algorithms for addressing large arrays

- by reve_etrange

I am trying to deal with a very large dataset. I have k = ~4200 matrices (varying sizes) which must be compared combinatorially, skipping non-unique and self comparisons. Each of k(k-1)/2 comparisons produces a matrix, which must be indexed against its parents (i.e. can find out where it came from). The convenient way to do this is to (triangularly) fill a k-by-k cell array with the result of each comparison. These are ~100 X ~100 matrices, on average. Using single precision floats, it works out to 400 GB overall. I need to 1) generate the cell array or pieces of it without trying to place the whole thing in memory and 2) access its elements (and their elements) in like fashion. My attempts have been inefficient due to reliance on MATLAB's eval() as well as save and clear occurring in loops. for i=1:k [~,m] = size(data{i}); cur_var = ['H' int2str(i)]; %# if i == 1; save('FileName'); end; %# If using a single MAT file and need to create it. eval([cur_var ' = cell(1,k-i);']); for j=i+1:k [~,n] = size(data{j}); eval([cur_var '{i,j} = zeros(m,n,''single'');']); eval([cur_var '{i,j} = compare(data{i},data{j});']); end save(cur_var,cur_var); %# Add '-append' when using a single MAT file. clear(cur_var); end The other thing I have done is to perform the split when mod((i+j-1)/2,max(factor(k(k-1)/2))) == 0. This divides the result into the largest number of same-size pieces, which seems logical. The indexing is a little more complicated, but not too bad because a linear index could be used. Does anyone know/see a better way?

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Strange results while measuring delta time on Linux

- by pachanga

Folks, could you please explain why I'm getting very strange results from time to time using the the following code: #include <unistd.h> #include <sys/time.h> #include <time.h> #include <stdio.h> int main() { struct timeval start, end; long mtime, seconds, useconds; while(1) { gettimeofday(&start, NULL); usleep(2000); gettimeofday(&end, NULL); seconds = end.tv_sec - start.tv_sec; useconds = end.tv_usec - start.tv_usec; mtime = ((seconds) * 1000 + useconds/1000.0) + 0.5; if(mtime > 10) printf("WTF: %ld\n", mtime); } return 0; } (You can compile and run it with: gcc test.c -o out -lrt && ./out) What I'm experiencing is sporadic big values of mtime variable almost every second or even more often, e.g: $ gcc test.c -o out -lrt && ./out WTF: 14 WTF: 11 WTF: 11 WTF: 11 WTF: 14 WTF: 13 WTF: 13 WTF: 11 WTF: 16 How can this be possible? Is it OS to blame? Does it do too much context switching? But my box is idle( load average: 0.02, 0.02, 0.3). Here is my Linux kernel version: $ uname -a Linux kurluka 2.6.31-21-generic #59-Ubuntu SMP Wed Mar 24 07:28:56 UTC 2010 i686 GNU/Linux

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Agile methodologies. Is it a by-product of mind control techniques as NLP / Scientology?

- by Bobb

The more I read about contemporary methods combinging scrum, tdd and xp, the more I feel like I already seen the methods. I am not arguing that agile approach is much more progressive than older rigid structures like waterfall, what I am saying is that it seems to me that agile methodologies are ideal to be used as a nest for a brainwashing business. I read few articles which kept referring to authors which I checked afterwards and they call themselves - coaches, trainers (usual thing when NLP specialists are involved) with no apparent software development history. Also I met a guy who is a scrum faciltator (term widly used in relation to scientology) in a high profile company. I talked to him less than 5 min but I got complete feeling that he is either on drugs or he has been programmed by a powerful NLP specialist. The way to talk and his body movements witnessed he is not an average normal person (in terms of normal distribution :))... Please dont get me wrong. I am not a fun of conspiracy theories. But I had an experience with a member of church of scientology tried to invade a commercial firm and actually went half way through to very top in just 3 weeks. I saw his work. For now I have complete impression is that psycho manipulators are now invading IT industry through the convenient door of agile techniques. Anyone has the same feeling/thoughts?

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How can I keep curl output out of mail from my cronjob?

- by Russell C.

I have written a Perl script that runs as a daily crontab job that uploads files to Amazon S3 via CURL. I want the output of the cron job emailed to me which works fine but I don't want that email to include messages related to the CURL upload (only those message my script is outputting). Here are the CURL related messages I'm seeing in the daily email right now: % Total % Received % Xferd Average Speed Time Time Time Current Dload Upload Total Spent Left Speed 0 230M 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0 0 230M 0 0 0 544k 0 1519k 0:02:35 --:--:-- 0:02:35 1807k 0 230M 0 0 0 1744k 0 1286k 0:03:03 0:00:01 0:03:02 1342k 1 230M 0 0 1 2880k 0 1219k 0:03:13 0:00:02 0:03:11 1250k 1 230M 0 0 1 4016k 0 1198k 0:03:17 0:00:03 0:03:14 1218k 2 230M 0 0 2 5168k 0 1186k 0:03:19 0:00:04 0:03:15 1202k 2 230M 0 0 2 6336k 0 1181k 0:03:19 0:00:05 0:03:14 1157k 3 230M 0 0 3 7488k 0 1177k 0:03:20 0:00:06 0:03:14 1147k 3 230M 0 0 3 8592k 0 1167k 0:03:22 0:00:07 0:03:15 1142k 4 230M 0 0 4 9744k 0 1166k 0:03:22 0:00:08 0:03:14 1145k 4 230M 0 0 4 10.6M 0 1163k 0:03:23 0:00:09 0:03:14 1142k 5 230M 0 0 5 11.7M 0 1161k 0:03:23 0:00:10 0:03:13 1140k 5 230M 0 0 5 12.8M 0 1158k 0:03:23 0:00:11 0:03:12 1133k 6 230M 0 0 6 13.9M 0 1155k 0:03:24 0:00:12 0:03:12 1138k 6 230M 0 0 6 15.0M 0 1155k 0:03:24 0:00:13 0:03:11 1138k 7 230M 0 0 7 16.1M 0 1152k 0:03:25 0:00:14 0:03:11 1131k 7 230M 0 0 7 17.2M 0 1152k 0:03:25 0:00:15 0:03:10 1132k 7 230M 0 0 7 18.4M 0 1152k 0:03:24 0:00:16 0:03:08 1140k I am using a simple Perl system() call to invoke CURL. Does anyone know what command line argument I can supply CURL to turn off the reporting of the upload progress?

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How to define 2-bit numbers in C, if possible?

- by Eddy

For my university process I'm simulating a process called random sequential adsorption. One of the things I have to do involves randomly depositing squares (which cannot overlap) onto a lattice until there is no more room left, repeating the process several times in order to find the average 'jamming' coverage %. Basically I'm performing operations on a large array of integers, of which 3 possible values exist: 0, 1 and 2. The sites marked with '0' are empty, the sites marked with '1' are full. Initially the array is defined like this: int i, j; int n = 1000000000; int array[n][n]; for(j = 0; j < n; j++) { for(i = 0; i < n; i++) { array[i][j] = 0; } } Say I want to deposit 5*5 squares randomly on the array (that cannot overlap), so that the squares are represented by '1's. This would be done by choosing the x and y coordinates randomly and then creating a 5*5 square of '1's with the topleft point of the square starting at that point. I would then mark sites near the square as '2's. These represent the sites that are unavailable since depositing a square at those sites would cause it to overlap an existing square. This process would continue until there is no more room left to deposit squares on the array (basically, no more '0's left on the array) Anyway, to the point. I would like to make this process as efficient as possible, by using bitwise operations. This would be easy if I didn't have to mark sites near the squares. I was wondering whether creating a 2-bit number would be possible, so that I can account for the sites marked with '2'. Sorry if this sounds really complicated, I just wanted to explain why I want to do this.

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ndarray field names for both row and column?

- by Graham Mitchell

I'm a computer science teacher trying to create a little gradebook for myself using NumPy. But I think it would make my code easier to write if I could create an ndarray that uses field names for both the rows and columns. Here's what I've got so far: import numpy as np num_stud = 23 num_assign = 2 grades = np.zeros(num_stud, dtype=[('assign 1','i2'), ('assign 2','i2')]) #etc gv = grades.view(dtype='i2').reshape(num_stud,num_assign) So, if my first student gets a 97 on 'assign 1', I can write either of: grades[0]['assign 1'] = 97 gv[0][0] = 97 Also, I can do the following: np.mean( grades['assign 1'] ) # class average for assignment 1 np.sum( gv[0] ) # total points for student 1 This all works. But what I can't figure out how to do is use a student id number to refer to a particular student (assume that two of my students have student ids as shown): grades['123456']['assign 2'] = 95 grades['314159']['assign 2'] = 83 ...or maybe create a second view with the different field names? np.sum( gview2['314159'] ) # total points for the student with the given id I know that I could create a dict mapping student ids to indices, but that seems fragile and crufty, and I'm hoping there's a better way than: id2i = { '123456': 0, '314159': 1 } np.sum( gv[ id2i['314159'] ] ) I'm also willing to re-architect things if there's a cleaner design. I'm new to NumPy, and I haven't written much code yet, so starting over isn't out of the question if I'm Doing It Wrong. I am going to be needing to sum all the assignment points for over a hundred students once a day, as well as run standard deviations and other stats. Plus, I'll be waiting on the results, so I'd like it to run in only a couple of seconds. Thanks in advance for any suggestions.

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I need a fast runtime expression parser

- by Chris Lively

I need to locate a fast, lightweight expression parser. Ideally I want to pass it a list of name/value pairs (e.g. variables) and a string containing the expression to evaluate. All I need back from it is a true/false value. The types of expressions should be along the lines of: varA == "xyz" and varB==123 Basically, just a simple logic engine whose expression is provided at runtime. UPDATE At minimum it needs to support ==, !=, , =, <, <= Regarding speed, I expect roughly 5 expressions to be executed per request. We'll see somewhere in the vicinity of 100/requests a second. Our current pages tend to execute in under 50ms. Usually there will only be 2 or 3 variables involved in any expression. However, I'll need to load approximately 30 into the parser prior to execution. UPDATE 2012/11/5 Update about performance. We implemented nCalc nearly 2 years ago. Since then we've expanded it's use such that we average 40+ expressions covering 300+ variables on post backs. There are now thousands of post backs occurring per second with absolutely zero performance degradation. We've also extended it to include a handful of additional functions, again with no performance loss. In short, nCalc met all of our needs and exceeded our expectations.

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How can I distribute x cakes amongst y people?

- by Rupert

I have an associative array with the ids of x cakes and another associative array with the ids of y people. I want to ensure that each cake is enjoyed by exactly 2 people and that each person gets a fair share of cake overall. However, cakes must be kept whole (i.e. if the average cake per person is a fraction, this fraction will be rounded up for some, and down for others). No person can be assigned the same cake twice. For example: $cake = array('id'=>'1','id'=>'2') $people = array('id'=>'1','id'=>'2','id'=>'3') In order to do so, I wish to create a new array where each row represents a cake-person assignment. As each cake is being assigned to two people, the number of rows in this table should be exactly twice the number of cakes. There will not be exactly 1 solution to this problem but a solution to the above example would be: $cake_person = array( '1'=>array('cake_id'=>'1', 'person_id'=>'1'), '2'=>array('cake_id'=>'1', 'person_id'=>'2'), '3'=>array('cake_id'=>'2', 'person_id'=>'2'), '4'=>array('cake_id'=>'2', 'person_id'=>'3'), ) Notice that people 1 and 3 are losing out but that is because there is no more cake to go around! Each cake must be given exactly twice. How can I generate such a solution reliably for larger numbers of people and cakes?

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