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  • problem with background subtraction

    - by riyana
    I'm doing background subtraction using opencv. The problem is the foreground object is not always detected correctly. To deal with this I would like to use four or five images, and take their average as the background image. How can I do that?

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  • How can I fall in love with Math? Again?

    - by gotts
    After reading How to not sort by average rating by Evan Miller I was really inspired to learn some more math. But after thinking about it for a while I didn't find a way I can use beyond-trivial math in my pet projects.. Or probably it is a moment like "You are not aware that you are not aware" and I should learn more math before I can start to see great examples of how I can apply it?

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  • Memory efficient int-int dict in Python

    - by Bolo
    Hi, I need a memory efficient int-int dict in Python that would support the following operations in O(log n) time: d[k] = v # replace if present v = d[k] # None or a negative number if not present I need to hold ~250M pairs, so it really has to be tight. Do you happen to know a suitable implementation (Python 2.7)? EDIT Removed impossible requirement and other nonsense. Thanks, Craig and Kylotan! To rephrase. Here's a trivial int-int dictionary with 1M pairs: >>> import random, sys >>> from guppy import hpy >>> h = hpy() >>> h.setrelheap() >>> d = {} >>> for _ in xrange(1000000): ... d[random.randint(0, sys.maxint)] = random.randint(0, sys.maxint) ... >>> h.heap() Partition of a set of 1999530 objects. Total size = 49161112 bytes. Index Count % Size % Cumulative % Kind (class / dict of class) 0 1 0 25165960 51 25165960 51 dict (no owner) 1 1999521 100 23994252 49 49160212 100 int On average, a pair of integers uses 49 bytes. Here's an array of 2M integers: >>> import array, random, sys >>> from guppy import hpy >>> h = hpy() >>> h.setrelheap() >>> a = array.array('i') >>> for _ in xrange(2000000): ... a.append(random.randint(0, sys.maxint)) ... >>> h.heap() Partition of a set of 14 objects. Total size = 8001108 bytes. Index Count % Size % Cumulative % Kind (class / dict of class) 0 1 7 8000028 100 8000028 100 array.array On average, a pair of integers uses 8 bytes. I accept that 8 bytes/pair in a dictionary is rather hard to achieve in general. Rephrased question: is there a memory-efficient implementation of int-int dictionary that uses considerably less than 49 bytes/pair?

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  • Why is go language so slow?

    - by oraz
    As we can see from The Computer Language Benchmarks Game: go is in average 10x slower then C go is 3x slower then Java !? How it can be bearing in mind that go compiler produces native code for execution? Immature compilers for go? Or there is some intrinsic problem with the go language?

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  • what does process geometry mean?

    - by wenlujon
    from ARM DDI 01001, there is a term: process geometry, does it mean the chip size? Caches and write buffers to improve average system performance are now commonplace in ARM® memory systems. Core clock rates have increased at a faster rate than memory access times over recent years. This factor, and smaller process geometries, the economics of on-chip memory, and system power constraints have encouraged the use of caches to meet growing system demands. thanks.

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  • Python. How to iterate through a list of lists looking for a partial match

    - by Becca Millard
    I'm completely stuck on this, without even an idea about how to wrap my head around the logic of this. In the first half of the code, I have successfully generation a list of (thousands of) lists of players names and efficiency scores: eg name_order_list = [["Bob", "Farley", 12.345], ["Jack", "Donalds", 14.567], ["Jack", "Donalds", 13.421], ["Jack", "Donalds", 15.232],["Mike", "Patricks", 10.543]] What I'm trying to do, is come up with a way to make a list of lists of the average efficiency of each player. So in that example, Jack Donalds appears multiple times, so I'd want to recognize his name somehow and average out the efficiency scores. Then sort that new list by efficiency, rather than name. So then the outcome would be like: average_eff_list = [[12.345, "Bob", "Farley"], [14.407, "Jack", "Donalds"], [10.543, "Mike", "Patricks"]] Here's what I tried (it's kind of a mess, but should be readable): total_list = [] odd_lines = [name_order_list[i] for i in range(len(name_order_list)) if i % 2 == 0] even_lines = [name_order_list[i] for i in range(len(name_order_list)) if i % 2 == 1] i = 0 j = i-1 while i <= 10650: iteration = 2 total_eff = 0 while odd_lines[i][0:2] == even_lines[i][0:2]: if odd_lines[i][0:2] == even_lines[j][0:2]: if odd_lines[j][0:2] != even_lines[j][0:2]: total_eff = even_lines[j][2]/(iteration-1) iteration -= 1 #account fr the single (rather than dual) additional entry else: total_eff = total_eff if iteration == 2: total_eff = (odd_lines[i][2] + even_lines[i][2]) / iteration else: total_eff = ((total_eff * (iteration - 2)) + (odd_lines[i][2] + even_lines[i][2])) / iteration iteration += 2 i += 1 j += 1 if i > 10650: break else: if odd_lines[i][0:2] == even_lines[j][0:2]: if odd_lines[j][0:2] != even_lines[j][0:2]: total_eff = (odd_lines[i][2] + even_lines[j][2]) / iteration else: total_eff = ((total_eff * (iteration -2)) + odd_lines[i][2]) / (iteration - 1) if total_eff == 0: #there's no match at all total_odd = [odd_lines[i][2], odd_lines[i][0], odd_lines[i][1]] total_list.append(total_odd) if even_lines[i][0:2] != odd_lines[i+1][0:2]: total_even = [even_lines[i][2], even_lines[i][0], even_lines[i][1]] else: total = [total_eff, odd_lines[i][0], odd_lines[i][1]] total_list.append(total) i += 1 if i > 10650: break else: print(total_list) Now, this runs well enough (doesn't get stuck or print someone's name multiple times) but the efficiency values are off by a large amount, so I know that scores are getting missed somewhere. This is a problem with my logic, I think, so any help would be greatly appreciated. As would any advice about how to loop through that massive list in a smarter way, since I'm sure there is one... EIDT: for this exercise, I need to keep it all in a list format. I can make new lists, but no using dictionaries, classes, etc.

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  • Financial Charts / Graphs in Ruby or Python

    - by Eric the Red
    What are my best options for creating a financial open-high-low-close (OHLC) chart in a high level language like Ruby or Python? While there seem to be a lot of options for graphing, I haven't seen any gems or eggs with this kind of chart. http://en.wikipedia.org/wiki/Open-high-low-close_chart (but I don't need the moving average or Bollinger bands) JFreeChart can do this in Java, but I'd like to make my codebase as small and simple as possible. Thanks!

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  • Curl CONNECTION OPTIONS

    - by cinek1lol
    HI I'd like to know how to check out the speed of a file being uploaded in real time using the curl library in c++. This is what I have written: curl_easy_getinfo(curl,CURLINFO_SPEED_UPLOAD,&c); But the manual says that it shows average speed, but even this doesn't seem to work with me, because I can only see a 0. There is one more thing: How to set an upload limit that works, because if I write this: curl_easy_setopt(curl, CURLOPT_MAX_SEND_SPEED_LARGE, 100); I get an error 502 message plis help

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  • Client ping to servers

    - by skarama
    Hi, I am wondering what would the best way to let visitors of a website ping various remote servers. Example: I am a visitor, I choose from a lsit of locations Paris, France and the script would ping from my location to Paris and return an average of x number of ping attempts. Any ideas?

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  • Using AVG() in Oracle SQL

    - by Viet Anh
    I have a table named Student as followed: CREATE TABLE "STUDENT" ( "ID" NUMBER(*,0), "NAME" VARCHAR2(20), "AGE" NUMBER(*,0), "CITY" VARCHAR2(20), PRIMARY KEY ("ID") ENABLE ) I am trying to get all the records of the students having a larger age than the average age. This is what I tried: SELECT * FROM student WHERE age > AVG(age) and SELECT * FROM student HAVING age > AVG(age) Both ways did not work!

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  • Input/ Output alternatives for printf/scanf

    - by Nitish
    It may sound strange that knowing a lot about ios and haing some experience in .net, I am a newcomer to C. Somewhere I got this target to find average of n numbers without using printf and scanf. I don't want the code for the program but it will be really helpful if someone can help me with the alternatives to the mentioned functions. Please let me know if code with printf/scanf is required here. Also do let me know if my query stands invalid. Thanks and Regards, Nitish

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  • How do I aggregate activerecord model data for a specific time period?

    - by gsiener
    I'm collecting data from a system every ~10s (this time difference varies due to communication time with networked devices). I'd like to calculate averages and sums of the stored values for this activerecord model on a daily basis. All records are stored in UTC. What's the correct way to sum and average values for, e.g., the previous day from midnight to midnight EST? I can do this in sql but don't know the "rails way" to make this calculation.

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  • Generate RTT values

    - by Jean Gauthier
    Hi all, I'm writing a Java applet where I should be able to simulate a connection between two hosts. Hence I have to generate packet round-trip times at random. These RTTs can go from ~0 to infinity, but are typically oscillating around some average value (i.e. an extremely large or small value is very improbable but possible). I was wondering if anyone had an idea of how I could do this? Thanks in advance

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  • SQL Query with computed column

    - by plotnick
    help me please with a query. Assume that we have a table with columns: Transaction StartTime EndTime Now, I need a query with computed column of (value = EndTime-Startime). Actually I need to group Users(Transaction has a FK for Users) and sort them by average time spent for transaction.

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  • How to define and work with an array of bits in C?

    - by Eddy
    I want to create a very large array on which I write '0's and '1's. I'm trying to simulate a physical process called random sequential adsorption, where units of length 2, dimers, are deposited onto an n-dimensional lattice at a random location, without overlapping each other. The process stops when there is no more room left on the lattice for depositing more dimers (lattice is jammed). Initially I start with a lattice of zeroes, and the dimers are represented by a pair of '1's. As each dimer is deposited, the site on the left of the dimer is blocked, due to the fact that the dimers cannot overlap. So I simulate this process by depositing a triple of '1's on the lattice. I need to repeat the entire simulation a large number of times and then work out the average coverage %. I've already done this using an array of chars for 1D and 2D lattices. At the moment I'm trying to make the code as efficient as possible, before working on the 3D problem and more complicated generalisations. This is basically what the code looks like in 1D, simplified: int main() { /* Define lattice */ array = (char*)malloc(N * sizeof(char)); total_c = 0; /* Carry out RSA multiple times */ for (i = 0; i < 1000; i++) rand_seq_ads(); /* Calculate average coverage efficiency at jamming */ printf("coverage efficiency = %lf", total_c/1000); return 0; } void rand_seq_ads() { /* Initialise array, initial conditions */ memset(a, 0, N * sizeof(char)); available_sites = N; count = 0; /* While the lattice still has enough room... */ while(available_sites != 0) { /* Generate random site location */ x = rand(); /* Deposit dimer (if site is available) */ if(array[x] == 0) { array[x] = 1; array[x+1] = 1; count += 1; available_sites += -2; } /* Mark site left of dimer as unavailable (if its empty) */ if(array[x-1] == 0) { array[x-1] = 1; available_sites += -1; } } /* Calculate coverage %, and add to total */ c = count/N total_c += c; } For the actual project I'm doing, it involves not just dimers but trimers, quadrimers, and all sorts of shapes and sizes (for 2D and 3D). I was hoping that I would be able to work with individual bits instead of bytes, but I've been reading around and as far as I can tell you can only change 1 byte at a time, so either I need to do some complicated indexing or there is a simpler way to do it? Thanks for your answers

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  • question with its query

    - by user329820
    Hi this is my homework and the question is this: List the average balance of customers by city and short zip code (the first five digits of thezip code). Only include customers residing in Washington State (‘WA’). also the Customer table has 5 columns(Name,Family,CustZip,CustCity,CustAVGBal) I wrote the query like below is this correct? SELECT CustCity,LEFT(CustZip,5) AS NewCustZip,CustAVGBal FROM Customer WHERE CustCity = 'WA' THANKS!!

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  • How to test my GAE site for performance

    - by Sergey Basharov
    I am building a GAE site that uses AJAX/JSON for almost all its tasks including building the UI elements, all interactions and client-server requests. What is a good way to test it for highloads so that I could have some statistics about how much resources 1000 average users per some period of time would take. I think I can create some Python functions for this purpose. What can you advise? Thanks.

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  • How long is too long for a script to execute?

    - by Chris T
    What is the max time do you think is acceptable for a web script (PHP for example) to execute before it starts to become an annoyance for the user (on average)? I always thought that if the user has to wait more than 1 second for the page to load (this of course after images and css have been cached..this rule really only applies for subsequent requests) they would start to get annoyed.

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  • Where is the money?

    - by Someone
    Big companies can afford higher salaries but it is harder to get noticed. Do you think that a talented programmer or somebody who is training himself to be really good could make more money in smaller companies? I think smaller companies have a lower average, but maybe great programmers can get much more. What do you think?

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  • What is the technical skill degree of your co-workers?

    - by bonefisher
    For now it has been around 4 years that I work as developer. Most of my team mates, from their tech-skill, programming ability and code practices view, are somewhere between junior and senior. In all my previous jobs, there was a real geek who was brilliant at coding/analyzing/lead, but the others were just 'average' programmers. How would you rank your co-workers as good developers from rank 1 (best) - 5 (worst) ?

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  • statical graph for my website

    - by rabeea
    i have a freelance work website where programmers bid on projects. i want to draw a bell curve/ normal distribution chart for the bids placed on each project to show the percentage of bids higher or lower than the average bid. is there any statistical tool available that could take the data from the site and draw a graph?

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  • Replace XML Bullet Points Found in Feed in Classic ASP

    - by StevieB
    Hey I am currently reading in a XML file which contains bullet list in the following container i.e. ? the average pension contribution rate for executive directors . I am having a problem with symbol directly before the text of each bullet point I want to remove it i.e Replace(text,"old","new") but i cant seem to find what value that bullet point actually is to replace of that makes sense. Thanks

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