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  • PHP Hashtable array optimisation.

    - by hiprakhar
    I made a PHP app which was taking about ~0.0070sec for execution. Now, I added a hashtable array with about 2000 values. Suddenly the time for execution has gone up to ~0.0700 secs. Almost 10 times the previous value. I tried commenting out the part where I was searching inside the hashtable array (but array was still left defined). Still, the execution time remains about ~0.0500secs. Array is something like: $subjectinfo = array( 'TPT753' => 'Industrial Training', 'TPT801' => 'High Polymeric Engineering', 'TPT802' => 'Corrosion Engineering', 'TPT803' => 'Decorative ,Industrial And High Performance Coatings', 'TPT851' => 'Project'); Is there any way to optimize this part? I cannot use Database as I am running this app on Google app engine which is still not supporting JDO database for php. Some more code from the app: function getsubjectinfo($name) { $subjectinfo = array( 'TPT753' => 'Industrial Training', 'TPT801' => 'High Polymeric Engineering', 'TPT802' => 'Corrosion Engineering', 'TPT803' => 'Decorative ,Industrial And High Performance Coatings', 'TPT851' => 'Project'); $name = str_replace("-", "", $name); $name = str_replace(" ", "", $name); if (isset($subjectinfo["$name"])) return "(".$subjectinfo["$name"].")"; else return ""; } Then I am using the following statement 2-3 times in the app: echo $key." ".$this->getsubjectinfo($key)

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  • Can this code be further optimized??

    - by kaki
    i understand that the code given below will not be compltely understood unless i explain my whole of previous and next lines of code. But this is part of the code which is causing so much of delay in my project and want to optimize this. i want to know which code part is faulty and how could this be replaced. i guess,few can say that use of this function is heavy compared and other ligher method are available to do this work please help, thanks in advance for i in range(len(lists)): save=database_index[lists[i]] #print save #if save[1]!='text0194'and save[1]!='text0526': using_data[save[0]]=save p=os.path.join("c:/begpython/wavnk/",str(str(str(save[1]).replace('phone','text'))+'.pm')) x1=open(p , 'r') x2=open(p ,'r') for i in range(6): x1.readline() x2.readline() gen = (float(line.partition(' ')[0]) for line in x1) r= min(enumerate(gen), key=lambda x: abs(x[1] - float(save[4]))) #print r[0] a1=linecache.getline(str(str(p).replace('.pm','.mcep')), (r[0]+1)) #print a1 p1=str(str(a1).rstrip('\n')).split(' ') #print p1 join_cost_index_end[save[0]]=p1 #print join_cost_index_end gen = (float(line.partition(' ')[0]) for line in x2) r= min(enumerate(gen), key=lambda x: abs(x[1] - float(save[3]))) #print r[0] a2=linecache.getline(str(str(p).replace('.pm','.mcep')), (r[0]+1)) #print a2 p2=str(str(a2).rstrip('\n')).split(' ') #print p2 join_cost_index_strt[save[0]]=p2 #print join_cost_index_strt j=j+1 #print j #print join_cost_index_end #print join_cost_index_strt enter code here here my database_index has about 2,50,000 entries`

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  • How to efficiently show many Images? (iPhone programming)

    - by Thomas
    In my application I needed something like a particle system so I did the following: While the application initializes I load a UIImage laserImage = [UIImage imageNamed:@"laser.png"]; UIImage *laserImage is declared in the Interface of my Controller. Now every time I need a new particle this code makes one: // add new Laserimage UIImageView *newLaser = [[UIImageView alloc] initWithImage:laserImage]; [newLaser setTag:[model.lasers count]-9]; [newLaser setBounds:CGRectMake(0, 0, 17, 1)]; [newLaser setOpaque:YES]; [self.view addSubview:newLaser]; [newLaser release]; Please notice that the images are only 17px * 1px small and model.lasers is a internal array to do all the calculating seperated from graphical output. So in my main drawing loop I set all the UIImageView's positions to the calculated positions in my model.lasers array: for (int i = 0; i < [model.lasers count]; i++) { [[self.view viewWithTag:i+10] setCenter:[[model.lasers objectAtIndex:i] pos]]; } I incremented the tags by 10 because the default is 0 and I don't want to move all the views with the default tag. So the animation looks fine with about 10 - 20 images but really gets slow when working with about 60 images. So my question is: Is there any way to optimize this without starting over in OpenGl ES? Thank you very much and sorry for my english! Greetings from Germany, Thomas

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  • Code bacteria: evolving mathematical behavior

    - by Stefano Borini
    It would not be my intention to put a link on my blog, but I don't have any other method to clarify what I really mean. The article is quite long, and it's in three parts (1,2,3), but if you are curious, it's worth the reading. A long time ago (5 years, at least) I programmed a python program which generated "mathematical bacteria". These bacteria are python objects with a simple opcode-based genetic code. You can feed them with a number and they return a number, according to the execution of their code. I generate their genetic codes at random, and apply an environmental selection to those objects producing a result similar to a predefined expected value. Then I let them duplicate, introduce mutations, and evolve them. The result is quite interesting, as their genetic code basically learns how to solve simple equations, even for values different for the training dataset. Now, this thing is just a toy. I had time to waste and I wanted to satisfy my curiosity. however, I assume that something, in terms of research, has been made... I am reinventing the wheel here, I hope. Are you aware of more serious attempts at creating in-silico bacteria like the one I programmed? Please note that this is not really "genetic algorithms". Genetic algorithms is when you use evolution/selection to improve a vector of parameters against a given scoring function. This is kind of different. I optimize the code, not the parameters, against a given scoring function.

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  • Poor execution plans when using a filter and CONTAINSTABLE in a query

    - by Paul McLoughlin
    We have an interesting problem that I was hoping someone could help to shed some light on. At a high level the problem is as below: The following query executes quickly (1 second): SELECT SA.* FROM cg.SEARCHSERVER_ACTYS AS SA JOIN CONTAINSTABLE(CG.SEARCHSERVER_ACTYS, NOTE, 'reports') AS T1 ON T1.[Key]=SA.UNIQUE_ID but if we add a filter to the query, then it takes approximately 2 minutes to return: SELECT SA.* FROM cg.SEARCHSERVER_ACTYS AS SA JOIN CONTAINSTABLE(CG.SEARCHSERVER_ACTYS, NOTE, 'reports') AS T1 ON T1.[Key]=SA.UNIQUE_ID WHERE SA.CHG_DATE'19 Feb 2010' Looking at the execution plan for the two queries, I can see that in the second case there are two places where there are huge differences between the actual and estimated number of rows, these being: 1) For the FulltextMatch table valued function where the estimate is approx 22,000 rows and the actual is 29 million rows (which are then filtered down to 1670 rows before the join) and 2) For the index seek on the full text index, where the estimate is 1 row and the actual is 13,000 rows As a result of the estimates, the optimiser is choosing to use a nested loops join (since it assumes a small number of rows) hence the plan is inefficient. We can work around the problem by either (a) parameterising the query and adding an OPTION (OPTIMIZE FOR UNKNOWN) to the query or (b) by forcing a HASH JOIN to be used. In both of these cases the query returns in sub 1 second and the estimates appear reasonable. My question really is 'why are the estimates being used in the poorly performing case so wildly inaccurate and what can be done to improve them'? Statistics are up to date on the indexes on the indexed view being used here. Any help greatly appreciated.

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  • MySQL efficiency as it relates to the database/table size

    - by mlissner
    I'm building a system using django, Sphinx and MySQL that's very quickly becoming quite large. The database currently has about 2000 rows, and I've written a program that's going to populate it with another 40,000 rows in a couple days. Since the database is live right now, and since I've never had a database with this much information in it, I'm worried about some things: Is adding all these rows going to seriously degrade the efficiency of my django app? Will I need to go back through it and optimize all my database calls so they're doing things more cleverly? Or will this make the database slow all around to the extent that I can't do anything about it at all? If you scoff at my 40k rows, then, my next question is, at what point SHOULD I be concerned? I will likely be adding another couple hundred thousand soon, so I worry, and I fret. How is sphinx going to feel about all this? Is it going to freak out when it realizes it has to index all this data? Or will it be fine? Is this normal for it? If it is, at what point should I be concerned that it's too much data for Sphinx? Thanks for any thoughts.

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  • How to Use Calculated Color Values with ColorMatrix?

    - by Otaku
    I am changing color values of each pixel in an image based on a calculation. The problem is that this takes over 5 seconds on my machine with a 1000x1333 image and I'm looking for a way to optimize it to be much faster. I think ColorMatrix may be an option, but I'm having a difficult time figure out how I would get a set of pixel RGB values, use that to calculate and then set the new pixel value. I can see how this can be done if I was just modifying (multiplying, subtracting, etc.) the original value with ColorMatrix, but now how I can use the pixels returned value to use it to calculate and new value. For example: Sub DarkenPicture() Dim clrTestFolderPath = "C:\Users\Me\Desktop\ColorTest\" Dim originalPicture = "original.jpg" Dim Luminance As Single Dim bitmapOriginal As Bitmap = Image.FromFile(clrTestFolderPath + originalPicture) Dim Clr As Color Dim newR As Byte Dim newG As Byte Dim newB As Byte For x = 0 To bitmapOriginal.Width - 1 For y = 0 To bitmapOriginal.Height - 1 Clr = bitmapOriginal.GetPixel(x, y) Luminance = ((0.21 * (Clr.R) + (0.72 * (Clr.G)) + (0.07 * (Clr.B))/ 255 newR = Clr.R * Luminance newG = Clr.G * Luminance newB = Clr.B * Luminance bitmapOriginal.SetPixel(x, y, Color.FromArgb(newR, newG, newB)) Next Next bitmapOriginal.Save(clrTestFolderPath + "colorized.jpg", ImageFormat.Jpeg) End Sub The Luminance value is the calculated one. I know I can set ColorMatrix's M00, M11, M22 to 0, 0, 0 respectively and then put a new value in M40, M41, M42, but that new value is calculated based of a value multiplication and addition of that pixel's components (((0.21 * (Clr.R) + (0.72 * (Clr.G)) + (0.07 * (Clr.B)) and the result of that - Luminance - is multiplied by the color component). Is this even possible with ColorMatrix?

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  • Mysql Server Optimization

    - by Ish Kumar
    Hi Geeks, We are having serious MySQL(InnoDB) performance issues at a moment when we do: (10-20) insertions on TABLE1 (10-20) updates on TABLE2 Note: Both above operations happens within fraction of a second. And this occurs every few (10-15) minutes. And all online users (approx 400-600) doing read operation on join of TABLE1 & TABLE2 every 1 second. Here is our mysql configuration info: http://docs.google.com/View?id=dfrswh7c_117fmgcmb44 Issues: Lot queries wait and expire later (saw it from phpmyadmin / processes). My poor MySQL server crashes sometimes Questions Q1: Any suggestions to optimize at MySQL level? Q2: I thinking to use persistent connections at application level, is it right? Info Added Later: Database Engine: InnoDB TABLE1 : 400,000 rows (inserting 8,000 daily) & TABLE2: 8,000 rows 1 second query: SELECT b.id, b.user_id, b.description, b.debit, b.created, b.price, u.username, u.email, u.mobile FROM TABLE1 b, TABLE2 u WHERE b.credit = 0 AND b.user_id = u.id AND b.auction_id = "12345" ORDER BY b.id DESC LIMIT 10; // there are few more but they are not so critical. Indexing is good, we are using them wisely. In above query all id's are indexed And TABLE1 has frequent insertions and TABLE2 has frequent updates.

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  • In .NET, What Is Fastest Way to Initialize Multi-Dimensional Array to Non-Default Value

    - by AMissico
    How do I initialize a multi-dimensional array of a primitive type as fast as possible? I am stuck with using multi-dimensional arrays. My problem is performance. The following routine initializes a 100x100 array in approx. 500 ticks. Removing the int.MaxValue initialization results in approx. 180 ticks just for the looping. Approximately 100 ticks to create the array without looping and without initializing to int.MaxValue. Routines similiar to this are called a few tens-of-thousands to several million times. I am open to suggestions on how to optimize this non-default initialization of an array. One idea I had is to use a smaller primitive type when available. For instance, using byte instead of int, saves 100 ticks. I would be happy with this, but I am hoping that I don't have to change the primitive data type. public int[,] CreateArray(Size size) { int[,] array = new int[size.Width, size.Height]; for (int x = 0; x < size.Width; x++) { for (int y = 0; y < size.Height; y++) { array[x, y] = int.MaxValue; } } return array; }

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  • Multiple threads modifying a collection in Java??

    - by posdef
    Hi, The project I am working on requires a whole bunch of queries towards a database. In principle there are two types of queries I am using: read from excel file, check for a couple of parameters and do a query for hits in the database. These hits are then registered as a series of custom classes. Any hit may (and most likely will) occur more than once so this part of the code checks and updates the occurrence in a custom list implementation that extends ArrayList. for each hit found, do a detail query and parse the output, so that the classes created in (I) get detailed info. I figured I would use multiple threads to optimize time-wise. However I can't really come up with a good way to solve the problem that occurs with the collection these items are stored in. To elaborate a little bit; throughout the execution objects are supposed to be modified by both (I) and (II). I deliberately didn't c/p any code, as it would be big chunks of code to make any sense.. I hope it make some sense with the description above. Thanks,

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  • What is a data structure for quickly finding non-empty intersections of a list of sets?

    - by Andrey Fedorov
    I have a set of N items, which are sets of integers, let's assume it's ordered and call it I[1..N]. Given a candidate set, I need to find the subset of I which have non-empty intersections with the candidate. So, for example, if: I = [{1,2}, {2,3}, {4,5}] I'm looking to define valid_items(items, candidate), such that: valid_items(I, {1}) == {1} valid_items(I, {2}) == {1, 2} valid_items(I, {3,4}) == {2, 3} I'm trying to optimize for one given set I and a variable candidate sets. Currently I am doing this by caching items_containing[n] = {the sets which contain n}. In the above example, that would be: items_containing = [{}, {1}, {1,2}, {2}, {3}, {3}] That is, 0 is contained in no items, 1 is contained in item 1, 2 is contained in itmes 1 and 2, 2 is contained in item 2, 3 is contained in item 2, and 4 and 5 are contained in item 3. That way, I can define valid_items(I, candidate) = union(items_containing[n] for n in candidate). Is there any more efficient data structure (of a reasonable size) for caching the result of this union? The obvious example of space 2^N is not acceptable, but N or N*log(N) would be.

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  • Why doesn't gcc remove this check of a non-volatile variable?

    - by Thomas
    This question is mostly academic. I ask out of curiosity, not because this poses an actual problem for me. Consider the following incorrect C program. #include <signal.h> #include <stdio.h> static int running = 1; void handler(int u) { running = 0; } int main() { signal(SIGTERM, handler); while (running) ; printf("Bye!\n"); return 0; } This program is incorrect because the handler interrupts the program flow, so running can be modified at any time and should therefore be declared volatile. But let's say the programmer forgot that. gcc 4.3.3, with the -O3 flag, compiles the loop body (after one initial check of the running flag) down to the infinite loop .L7: jmp .L7 which was to be expected. Now we put something trivial inside the while loop, like: while (running) putchar('.'); And suddenly, gcc does not optimize the loop condition anymore! The loop body's assembly now looks like this (again at -O3): .L7: movq stdout(%rip), %rsi movl $46, %edi call _IO_putc movl running(%rip), %eax testl %eax, %eax jne .L7 We see that running is re-loaded from memory each time through the loop; it is not even cached in a register. Apparently gcc now thinks that the value of running could have changed. So why does gcc suddenly decide that it needs to re-check the value of running in this case?

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  • Solver Foundation Optimization - 1D Bin Packing

    - by Val Nolav
    I want to optimize loading marbles into trucks. I do not know, if I can use Solver Foundation class for that purpose. Before, I start writing code, I wanted to ask it here. 1- Marbles can be in any weight between 1 to 24 Tons. 2 - A truck can hold maximum of 24 Tons. 3- It can be loaded as many marble cubes, as it can take for upto 24 tones, which means there is no Volume limitation. 4- There can be between 200 up to 500 different marbles depending on time. GOAL - The goal is to load marbles in minimum truck shipment. How can I do that without writing a lot of if conditions and for loops? Can I use Microsoft Solver Foundation for that purpose? I read the documentation provided by Microsoft however, I could not find a scenario similar to mine. M1+ M2 + M3 + .... Mn <=24 this is for one truck shipment. Let say there are 200 different Marbles and Marble weights are Float. Thanks

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  • Maximizing the number of true concurrent / parrallel http requests in Silverlight

    - by Clems
    Hi all. I'm using SL 4 beta and my app needs to do a lot of small http requests to the server. I believe that when exceeding the number of allowed concurrent requests, the subsequent requests are put in a queue. I am also aware that SL 4 has both a http browser stack and a http client stack, with both different limit in terms of the number of concurrent requests. Let's say call those limits MAX_BROWSER and MAX_CLIENT. Also I think I read somewhere that the number of concurrent requests is limited per domain, not overall. But I'm sure if this applies to both the http client stack. That means that you CAN have MAX_BROWSER requests to domain1.com AND MAX_BROWSER requests to domain2.com at the same time. And I even believe that sub domains are considered different so you can also have MAX_BROWSER requests to domain1.com AND MAX_BROWSER requests to sub.domain1.com at the same time. I have ownership of the services and domain names so I could easily setup sub domains for my services. Given those considerations I'm trying to optimize the number of concurrent http requests to my server. Here are few questions ? Is is possible to use both stack at the same time ? Is the subdomain/domain story true for both stacks ? None ? If so that would mean that I could potentially have a number of concurrent requests equal to : (MAX_BROWSER + MAX_CLIENT) * NUMBER_OF_DOMAINS which would be fairly good. Is this correct ? I'm kind of sharing my morning thoughts here, hoping somebody has experimented with those things. Thank you.

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  • Need advice on comparing the performance of 2 equivalent linq to sql queries

    - by uvita
    I am working on tool to optimize linq to sql queries. Basically it intercepts the linq execution pipeline and makes some optimizations like for example removing a redundant join from a query. Of course, there is an overhead in the execution time before the query gets executed in the dbms, but then, the query should be processed faster. I don't want to use a sql profiler because I know that the generated query will be perform better in the dbms than the original one, I am looking for a correct way of measuring the global time between the creation of the query in linq and the end of its execution. Currently, I am using the Stopwatch class and my code looks something like this: var sw = new Stopwatch(); sw.Start(); const int amount = 100; for (var i = 0; i < amount; i++) { ExecuteNonOptimizedQuery(); } sw.Stop(); Console.Writeline("Executing the query {2} times took: {0}ms. On average, each query took: {1}ms", sw.ElapsedMilliseconds, sw.ElapsedMilliseconds / amount, amount); Basically the ExecutenNonOptimizedQuery() method creates a new DataContext, creates a query and then iterates over the results. I did this for both versions of the query, the normal one and the optimized one. I took the idea from this post from Frans Bouma. Is there any other approach/considerations I should take? Thanks in advance!

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  • Please help optimizing a long running query (left outer join, with 2 subqueries)

    - by 46and2
    Hi all. The query I need help with is: SELECT d.bn, d.4700, d.4500, ... , p.`Activity Description` FROM ( SELECT temp.bn, temp.4700, temp.4500, .... FROM `tdata` temp GROUP BY temp.bn HAVING (COUNT(temp.bn) = 1) ) d LEFT OUTER JOIN ( SELECT temp2.bn, max(temp2.FPE) AS max_fpe, temp2.`Activity Description` FROM `pdata` temp2 GROUP BY temp2.bn ) p ON p.bn = d.bn; The ... represents other fields that aren't really important to solving this problem. The issue is on the the second subquery - it is not using the index I have created and I am not sure why, it seems to be because of the way TEXT fields are handled. The first subquery uses the index I have created and runs quite snappy, however an explain on the second shows a 'Using temporary; Using filesort'. Please see the indexes I have created in the below table create statements. Can anyone help me optimize this? By way of quick explanation the first subquery is meant to only select records that have unique bn's, the second, while it looks a bit wacky (with the max function there which is not being used in the result set) is making sure that only one record from the right part of the join is included in the result set. My table create statements are CREATE TABLE `tdata` ( `BN` varchar(15) DEFAULT NULL, `4000` varchar(3) DEFAULT NULL, `5800` varchar(3) DEFAULT NULL, .... KEY `BN` (`BN`), KEY `idx_t3010`(`BN`,`4700`,`4500`,`4510`,`4520`,`4530`,`4570`,`4950`,`5000`,`5010`,`5020`,`5050`,`5060`,`5070`,`5100`) ) ENGINE=MyISAM DEFAULT CHARSET=utf8 CREATE TABLE `pdata` ( `BN` varchar(15) DEFAULT NULL, `FPE` datetime DEFAULT NULL, `Activity Description` text, .... KEY `BN` (`BN`), KEY `idx_programs_2009` (`BN`,`FPE`,`Activity Description`(100)) ) ENGINE=MyISAM DEFAULT CHARSET=utf8 Thanks!

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  • Speedup writing C programs using a subset of the Python syntax

    - by psihodelia
    I am constantly trying to optimize my time. Writing a C code takes a lot of time and requires much more keyboard touches than say writing a Python program. However, in order to speed up the time required to create a C program, one can automatize many things. I'd like to write my programs using smth. like Python but with C semantics. It means, all keywords are C keywords, but syntax is optimized. For example, this C code: #include "dsplib.h" #include "coeffs.h" #define MODULENAME "dsplib" #define NUM_SAMPLES 320 typedef float t_Vec; typedef struct s_Inter { char *pc_Name; struct s_Inter *px_Next; }t_Inter; typedef struct s_DspLibControl { t_Vec f_Y; }t_DspLibControl; void v_DspLibName(void) { printf("Module: %s", MODULENAME); printf("\n"); } int v_DspLibInitInterControl(t_DspLibControl *px_Con) { int y; px_Con->f_Y = 0.0; for(int i=0;i<10;i++) { y += i * i; } return y; } in optimized pythonized version can look like: include dsplib, coeffs define MODULENAME="dsplib", NUM_SAMPLES=320 typedef float t_Vec typedef struct s_Inter: char *pc_Name struct s_Inter *px_Next t_Inter typedef struct s_DspLibControl: t_Vec f_Y t_DspLibControl v_DspLibName(): printf("Module: %s", MODULENAME); printf("\n") int v_DspLibInitInterControl(t_DspLibControl *px_Con): int y px_Con->f_Y = 0.0 for int i=0;i<10;i++: y += i * i return y My question is: Do you know any VIM script, which allows to translate an original pythonized C code into a standard C code? For example, one is writing a C code but uses pythonized syntax, once she decides to translate pythonized blocks into standard C, she selects such blocks and press some key. And she doesn't save such pythonized code of course, VIM translates it into standard C.

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  • Netty options for real-time distribution of small messages to a large number of clients?

    - by user439407
    I am designing a (near) real-time Netty server to distribute a large number of very small messages to a large number of clients across the internet. In internal, go as fast as you can testing, I found that I could do 10k clients no sweat, but now that we are trying to go across the internet, where the latency, bandwidth etc varies pretty wildly we are running into the dreaded outOfMemory issues, even with 2 gigs of RAM. I have tried various workarounds(setting the socket stack sizes smaller, setting high and low water marks, cancelling things that are too old), and they help a little, but they seem to only help a little bit. What would some good ways to optimize Netty for sending large #s of small messages without significant delays? Also, the bulk of the message only consists of one kind of message that I don't particularly care if it doesn't arrive. I would use UDP but because we don't control the client, thats not really a possibility. Is it possible to set a separate timeout solely for this kind of message without affecting the other messages? Any insight you could offer would be greatly appreciated.

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  • What is the the relation between programming and mathematics?

    - by Math Grad
    Programmers seem to think that their work is quite mathematical. I understand this when you try to optimize something in performance, find the most efficient alogithm, etc.. But it patently seems false when you look at a billing application for a shop, or a systems software riddled with I/O calls. So what is it exactly? Is computation and associated programming really mathematical? Here I have in mind particularly the words of the philosopher Schopenhauer in mind: That arithmetic is the basest of all mental activities is proved by the fact that it is the only one that can be accomplished by means of a machine. Take, for instance, the reckoning machines that are so commonly used in England at the present time, and solely for the sake of convenience. But all analysis finitorum et infinitorum is fundamentally based on calculation. Therefore we may gauge the “profound sense of the mathematician,” of whom Lichtenberg has made fun, in that he says: “These so-called professors of mathematics have taken advantage of the ingenuousness of other people, have attained the credit of possessing profound sense, which strongly resembles the theologians’ profound sense of their own holiness.” I lifted the above quote from here. It seems that programmers are doing precisely the sort of mechanized base mental activity the grand old man is contemptuous about. So what exactly is the deal? Is programming really the "good" kind of mathematics, or just the baser type, or altogether something else just meant for business not to be confused with a pure discipline?

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  • (x86) Assembler Optimization

    - by Pindatjuh
    I'm building a compiler/assembler/linker in Java for the x86-32 (IA32) processor targeting Windows. High-level concepts of a "language" (in essential a Java API for creating executables) are translated into opcodes, which then are wrapped and outputted to a file. The translation process has several phases, one is the translation between languages: the highest-level code is translated into the medium-level code which is then translated into the lowest-level code (probably more than 3 levels). My problem is the following; if I have higher-level code (X and Y) translated to lower-level code (x, y, U and V), then an example of such a translation is, in pseudo-code: x + U(f) // generated by X + V(f) + y // generated by Y (An easy example) where V is the opposite of U (compare with a stack push as U and a pop as V). This needs to be 'optimized' into: x + y (essentially removing the "useless" code) My idea was to use regular expressions. For the above case, it'll be a regular expression looking like this: x:(U(x)+V(x)):null, meaning for all x find U(x) followed by V(x) and replace by null. Imagine more complex regular expressions, for more complex optimizations. This should work on all levels. What do you suggest? What would be a good approach to optimize in these situations?

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  • Good Starting Points for Optimizing Database Calls in Ruby on Rails?

    - by viatropos
    I have a menu in Rails which grabs a nested tree of Post models, each which have a Slug model associated via a polymorphic association (using the friendly_id gem for slugs and awesome_nested_set for the tree). The database output in development looks like this (here's the full gist): SQL (0.4ms) SELECT COUNT(*) AS count_id FROM "posts" WHERE ("posts".parent_id = 39) CACHE (0.0ms) SELECT "posts".* FROM "posts" WHERE ("posts"."id" = 13) LIMIT 1 CACHE (0.0ms) SELECT "slugs".* FROM "slugs" WHERE ("slugs".sluggable_id = 13 AND "slugs".sluggable_type = 'Post') ORDER BY id DESC LIMIT 1 Slug Load (0.4ms) SELECT "slugs".* FROM "slugs" WHERE ("slugs".sluggable_id = 40 AND "slugs".sluggable_type = 'Post') ORDER BY id DESC LIMIT 1 SQL (0.3ms) SELECT COUNT(*) AS count_id FROM "posts" WHERE ("posts".parent_id = 40) CACHE (0.0ms) SELECT "posts".* FROM "posts" WHERE ("posts"."id" = 13) LIMIT 1 CACHE (0.0ms) SELECT "slugs".* FROM "slugs" WHERE ("slugs".sluggable_id = 13 AND "slugs".sluggable_type = 'Post') ORDER BY id DESC LIMIT 1 Slug Load (0.4ms) SELECT "slugs".* FROM "slugs" WHERE ("slugs".sluggable_id = 41 AND "slugs".sluggable_type = 'Post') ORDER BY id DESC LIMIT 1 ... Rendered shared/_menu.html.haml (907.6ms) What are some quick things I should always do to optimize this from the start (easy things)? Some things I'm thinking now are: Can Rails 3 eager load the whole Post tree + associated Slugs in one DB call? Can I do that easily with named scopes or custom SQL? What is best practice in this situation? Not really thinking about memcached in this situation as that can be applied to much more than just this.

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  • QuadTrees - how to update when internal items are moving

    - by egarcia
    I've implemented a working QuadTree. It subdivides 2-d space in order to accomodate items, identified by their bounding box (x,y,width,height) on the smallest possible quad (up to a minimum area). My code is based on this implementation (mine is in Lua instead of C#) : http://www.codeproject.com/KB/recipes/QuadTree.aspx I've been able to successfully implement insertions and deletions successfully. I've turn now my attention to the update() function, since my items' position and dimensions change over time. My first implementation works, but it is quite naïve: function QuadTree:update(item) self:remove(item) return self.root:insert(item) end Yup, I basically remove and reinsert every item every time they move. This works, but I'd like to optimize it a bit more; after all, most of the time, moving items still remain on the same quadTree node most of the iterations. Is there any standard way to deal with this kind of update? In case it helps, my code is here: http://github.com/kikito/passion/blob/master/ai/QuadTree.lua I'm not looking for someone to implement it for me; pointers to an existing working implementation (even in other languages) would suffice.

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  • SQLAlchemy: select over multiple tables

    - by ahojnnes
    Hi, I wanted to optimize my database query: link_list = select( columns=[link_table.c.rating, link_table.c.url, link_table.c.donations_in], whereclause=and_( not_(link_table.c.id.in_( select( columns=[request_table.c.recipient], whereclause=request_table.c.donator==donator.id ).as_scalar() )), link_table.c.id!=donator.id, ), limit=20, ).execute().fetchall() and tried to merge those two selects in one query: link_list = select( columns=[link_table.c.rating, link_table.c.url, link_table.c.donations_in], whereclause=and_( link_table.c.active==True, link_table.c.id!=donator.id, request_table.c.donator==donator.id, link_table.c.id!=request_table.c.recipient, ), limit=20, order_by=[link_table.c.rating.desc()] ).execute().fetchall() the database-schema looks like: link_table = Table('links', metadata, Column('id', Integer, primary_key=True, autoincrement=True), Column('url', Unicode(250), index=True, unique=True), Column('registration_date', DateTime), Column('donations_in', Integer), Column('active', Boolean), ) request_table = Table('requests', metadata, Column('id', Integer, primary_key=True, autoincrement=True), Column('recipient', Integer, ForeignKey('links.id')), Column('donator', Integer, ForeignKey('links.id')), Column('date', DateTime), ) There are several links (donator) in request_table pointing to one link in the link_table. I want to have links from link_table, which are not yet "requested". But this does not work. Is it actually possible, what I'm trying to do? If so, how would you do that? Thank you very much in advance!

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  • How do I update a progress bar in Cocoa during a long running loop?

    - by Nic
    Hi, I've got a while loop, that runs for many seconds and that's why I want to update a progress bar (NSProgressIndicator) during that process, but it updates only once after the loop has finished. The same happens if I want to update a label text, by the way. I believe, my loop prevents other things of that application to happen. There must be another technique. Does this have to do with threads or something? Am I on the right track? Can someone please give me a simple example, how to “optimize” my application? My application is a Cocoa Application (Xcode 3.2.1) with these two methods in my Example_AppDelegate.m: // This method runs when a start button is clicked. - (IBAction)startIt:(id)sender { [progressbar setDoubleValue:0.0]; [progressbar startAnimation:sender]; running = YES; // this is a instance variable int i = 0; while (running) { if (i++ = processAmount) { // processAmount is something like 1000000 running = NO; continue; } // Update progress bar double progr = (double)i / (double)processAmount; NSLog(@"progr: %f", progr); // Logs values between 0.0 and 1.0 [progressbar setDoubleValue:progr]; [progressbar needsDisplay]; // Do I need this? // Do some more hard work here... } } // This method runs when a stop button is clicked, but as long // as -startIt is busy, a click on the stop button does nothing. - (IBAction)stopIt:(id)sender { NSLog(@"Stop it!"); running = NO; [progressbar stopAnimation:sender]; } I'm really new to Objective-C, Cocoa and applications with a UI. Thank you very much for any helpful answer.

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  • Optimization headers for UITableView?

    - by Pask
    I have an optimization problem for the headers of a table with plain style. If I use the standard view for the table (the classic gray with titles set by titleForHeaderInSection:) everything is ok and the scrolling is smooth and immediate. When, instead, use this code to set my personal view: - (UIView *)tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section { return [self headerPerTitolo:[titoliSezioni objectAtIndex:section]]; } - (UIImageView *)headerPerTitolo:(NSString *)titolo { UIImageView *headerView = [[[UIImageView alloc] initWithFrame:CGRectMake(10.0, 0.0, 320.0, 44.0)] autorelease]; headerView.image = [UIImage imageNamed:kNomeImmagineHeader]; headerView.alpha = kAlphaSezioniTablePlain; UILabel * headerLabel = [[[UILabel alloc] initWithFrame:CGRectZero] autorelease]; headerLabel.backgroundColor = [UIColor clearColor]; headerLabel.opaque = NO; headerLabel.textColor = [UIColor whiteColor]; headerLabel.font = [UIFont boldSystemFontOfSize:16]; headerLabel.frame = CGRectMake(10.0,-11.0, 320.0, 44.0); headerLabel.textAlignment = UITextAlignmentLeft; headerLabel.text = titolo; [headerView addSubview:headerLabel]; return headerView; } scrolling is jerky and not immediate (sliding the finger on the screen does not match an immediate shift of the table). I do not know what caused this problem, maybe the fact that every time the method viewForHeaderInSection: is called, the code runs to create a new UIImageView. I tried many ways to solve the problem, such as creating an array of all the necessary view: apart from more time spent loading at startup, there is a continuing problem of low reactivity of the table. 've Attempted by reducing the size of UIImageView positioned from about 66 KB to 4 KB: not only has a deterioration in quality of colors (which distorts a bit 'original graphics), but ... the problem persists! Perhaps you have suggestions about it, or know me obscure techniques that enable me to optimize this aspect of my application ... I apologize for my English, I used Google for translation.

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