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  • what are all the Optimize tricks that you know for asp.net code ?

    - by Aristos
    After some time of many code programming on asp.net, I discover the very big speed different between string and StringBuilder. I know that is very common and known but I just mention it for start. The second think that I have found to speed up the code, is to use the const, and not the static, for declare my configuration constants value (especial the strings). With the const, the compiler not create new object, but just place the value, on the point that you have ask it, but with the static declaration, is create a new memory object and keep its on the memory. My third trick, is when I search for string, I use hash values, and not the string itself. For example, if I need a List<string SomeValues, and place inside strings that I need to search them, I prefer to use List<int SomeHashValue, and I use the hash value to locate the strings. My forth thought that I was wandering, is if is better to place big strings in one line, or separate them in different lines with the + symbol to be more easy to read out. I make some tests and see that the compiler make a good job is some split the string, in many lines, using the + symbol. What other tricks/tips do you know and use on your programming to make it run faster, and maybe use less memory. Well I know, that some times, to make something run faster, you need more memory, more cache. My priority is on speed. Because Speed Counts.

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  • Why does adding Crossover to my Genetic Algorithm give me worse results?

    - by MahlerFive
    I have implemented a Genetic Algorithm to solve the Traveling Salesman Problem (TSP). When I use only mutation, I find better solutions than when I add in crossover. I know that normal crossover methods do not work for TSP, so I implemented both the Ordered Crossover and the PMX Crossover methods, and both suffer from bad results. Here are the other parameters I'm using: Mutation: Single Swap Mutation or Inverted Subsequence Mutation (as described by Tiendil here) with mutation rates tested between 1% and 25%. Selection: Roulette Wheel Selection Fitness function: 1 / distance of tour Population size: Tested 100, 200, 500, I also run the GA 5 times so that I have a variety of starting populations. Stop Condition: 2500 generations With the same dataset of 26 points, I usually get results of about 500-600 distance using purely mutation with high mutation rates. When adding crossover my results are usually in the 800 distance range. The other confusing thing is that I have also implemented a very simple Hill-Climbing algorithm to solve the problem and when I run that 1000 times (faster than running the GA 5 times) I get results around 410-450 distance, and I would expect to get better results using a GA. Any ideas as to why my GA performing worse when I add crossover? And why is it performing much worse than a simple Hill-Climb algorithm which should get stuck on local maxima as it has no way of exploring once it finds a local max?

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  • Should i use HttpResponse.End() for a fast webapp?

    - by acidzombie24
    HttpResponse.End() seems to throw an exception according to msdn. Right now i have the choice of returning a value to say end thread (it only goes 2 functions deep) or i can call end(). I know that throwing exceptions is significantly slower (read the comment for a C#/.NET test) so if i want a fast webapp should i consider not calling it when it is trivially easy to not call it? -edit- I do have a function call in certain functions and in the constructor in classes to ensure the user is logged in. So i call HttpResponse.End() in enough places although hopefully in regular site usage it doesn't occur too often.

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  • How can I track the last location of a shipment effeciently using latest date of reporting?

    - by hash
    I need to find the latest location of each cargo item in a consignment. We mostly do this by looking at the route selected for a consignment and then finding the latest (max) time entered against nodes of this route. For example if a route has 5 nodes and we have entered timings against first 3 nodes, then the latest timing (max time) will tell us its location among the 3 nodes. I am really stuck on this query regarding performance issues. Even on few hundred rows, it takes more than 2 minutes. Please suggest how can I improve this query or any alternative approach I should acquire? Note: ATA= Actual Time of Arrival and ATD = Actual Time of Departure SELECT DISTINCT(c.id) as cid,c.ref as cons_ref , c.Name, c.CustRef FROM consignments c INNER JOIN routes r ON c.Route = r.ID INNER JOIN routes_nodes rn ON rn.Route = r.ID INNER JOIN cargo_timing ct ON c.ID=ct.ConsignmentID INNER JOIN (SELECT t.ConsignmentID, Max(t.firstata) as MaxDate FROM cargo_timing t GROUP BY t.ConsignmentID ) as TMax ON TMax.MaxDate=ct.firstata AND TMax.ConsignmentID=c.ID INNER JOIN nodes an ON ct.routenodeid = an.ID INNER JOIN contract cor ON cor.ID = c.Contract WHERE c.Type = 'Road' AND ( c.ATD = 0 AND c.ATA != 0 ) AND (cor.contract_reference in ('Generic','BP001','020-543-912')) ORDER BY c.ref ASC

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  • Why index_merge is not used here using MySQL?

    - by user198729
    Setup: mysql> create table t(a integer unsigned,b integer unsigned); mysql> insert into t(a,b) values (1,2),(1,3),(2,4); mysql> create index i_t_a on t(a); mysql> create index i_t_b on t(b); mysql> explain select * from t where a=1 or b=4; +----+-------------+-------+------+---------------+------+---------+------+------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+------+---------------+------+---------+------+------+-------------+ | 1 | SIMPLE | t | ALL | i_t_a,i_t_b | NULL | NULL | NULL | 3 | Using where | +----+-------------+-------+------+---------------+------+---------+------+------+-------------+ Is there something I'm missing? Update mysql> explain select * from t where a=1 or b=4; +----+-------------+-------+------+---------------+------+---------+------+------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+------+---------------+------+---------+------+------+-------------+ | 1 | SIMPLE | t | ALL | i_t_a,i_t_b | NULL | NULL | NULL | 1863 | Using where | +----+-------------+-------+------+---------------+------+---------+------+------+-------------+ Version: mysql> select version(); +----------------------+ | version() | +----------------------+ | 5.1.36-community-log | +----------------------+

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  • Can this MySQL subquery be optimised?

    - by Dan
    I have two tables, news and news_views. Every time an article is viewed, the news id, IP address and date is recorded in news_views. I'm using a query with a subquery to fetch the most viewed titles from news, by getting the total count of views in the last 24 hours for each one. It works fine except that it takes between 5-10 seconds to run, presumably because there's hundreds of thousands of rows in news_views and it has to go through the entire table before it can finish. The query is as follows, is there any way at all it can be improved? SELECT n.title , nv.views FROM news n LEFT JOIN ( SELECT news_id , count( DISTINCT ip ) AS views FROM news_views WHERE datetime >= SUBDATE(now(), INTERVAL 24 HOUR) GROUP BY news_id ) AS nv ON nv.news_id = n.id ORDER BY views DESC LIMIT 15

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  • Fast read of certain bytes of multiple files in C/C++

    - by Alejandro Cámara
    I've been searching in the web about this question and although there are many similar questions about read/write in C/C++, I haven't found about this specific task. I want to be able to read from multiple files (256x256 files) only sizeof(double) bytes located in a certain position of each file. Right now my solution is, for each file: Open the file (read, binary mode): fstream fTest("current_file", ios_base::out | ios_base::binary); Seek the position I want to read: fTest.seekg(position*sizeof(test_value), ios_base::beg); Read the bytes: fTest.read((char *) &(output[i][j]), sizeof(test_value)); And close the file: fTest.close(); This takes about 350 ms to run inside a for{ for {} } structure with 256x256 iterations (one for each file). Q: Do you think there is a better way to implement this operation? How would you do it?

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  • What's the best way to measure and track performance over various calls at runtime?

    - by bitcruncher
    Hello. I'm trying to optimize the performance of my code, but I'm not familiar with xcode's debuggers or debuggers in general. Is it possible to track the execution time and frequency of calls being made at runtime? Imagine a chain of events with some recursive calls over a fraction of a second. What's the best way to track where the CPU spends most of its time? Many thanks. Edit: Maybe this is better asked by saying, how do I use the xcode debug tools to do a stack trace?

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  • Design for a Debate club assignment application

    - by Amir Rachum
    Hi all, For my university's debate club, I was asked to create an application to assign debate sessions and I'm having some difficulties as to come up with a good design for it. I will do it in Java. Here's what's needed: What you need to know about BP debates: There are four teams of 2 debaters each and a judge. The four groups are assigned a specific position: gov1, gov2, op1, op2. There is no significance to the order within a team. The goal of the application is to get as input the debaters who are present (for example, if there are 20 people, we will hold 2 debates) and assign them to teams and roles with regards to the history of each debater so that: Each debater should debate with (be on the same team) as many people as possible. Each debater should uniformly debate in different positions. The debate should be fair - debaters have different levels of experience and this should be as even as possible - i.e., there shouldn't be a team of two very experienced debaters and a team of junior debaters. There should be an option for the user to restrict the assignment in various ways, such as: Specifying that two people should debate together, in a specific position or not. Specifying that a single debater should be in a specific position, regardless of the partner. etc... If anyone can try to give me some pointers for a design for this application, I'll be so thankful! Also, I've never implemented a GUI before, so I'd appreciate some pointers on that as well, but it's not the major issue right now.

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  • help me improve my sse yuv to rgb ssse3 code

    - by David McPaul
    Hello, I am looking to optimise some sse code I wrote for converting yuv to rgb (both planar and packed yuv functions). i am using SSSE3 at the moment but if there are useful functions from later sse versions thats ok. I am mainly interested in how I would work out processor stalls and the like. Anyone know of any tools that do static analysis of sse code? ; ; Copyright (C) 2009-2010 David McPaul ; ; All rights reserved. Distributed under the terms of the MIT License. ; ; A rather unoptimised set of ssse3 yuv to rgb converters ; does 8 pixels per loop ; inputer: ; reads 128 bits of yuv 8 bit data and puts ; the y values converted to 16 bit in xmm0 ; the u values converted to 16 bit and duplicated into xmm1 ; the v values converted to 16 bit and duplicated into xmm2 ; conversion: ; does the yuv to rgb conversion using 16 bit integer and the ; results are placed into the following registers as 8 bit clamped values ; r values in xmm3 ; g values in xmm4 ; b values in xmm5 ; outputer: ; writes out the rgba pixels as 8 bit values with 0 for alpha ; xmm6 used for scratch ; xmm7 used for scratch %macro cglobal 1 global _%1 %define %1 _%1 align 16 %1: %endmacro ; conversion code %macro yuv2rgbsse2 0 ; u = u - 128 ; v = v - 128 ; r = y + v + v >> 2 + v >> 3 + v >> 5 ; g = y - (u >> 2 + u >> 4 + u >> 5) - (v >> 1 + v >> 3 + v >> 4 + v >> 5) ; b = y + u + u >> 1 + u >> 2 + u >> 6 ; subtract 16 from y movdqa xmm7, [Const16] ; loads a constant using data cache (slower on first fetch but then cached) psubsw xmm0,xmm7 ; y = y - 16 ; subtract 128 from u and v movdqa xmm7, [Const128] ; loads a constant using data cache (slower on first fetch but then cached) psubsw xmm1,xmm7 ; u = u - 128 psubsw xmm2,xmm7 ; v = v - 128 ; load r,b with y movdqa xmm3,xmm0 ; r = y pshufd xmm5,xmm0, 0xE4 ; b = y ; r = y + v + v >> 2 + v >> 3 + v >> 5 paddsw xmm3, xmm2 ; add v to r movdqa xmm7, xmm1 ; move u to scratch pshufd xmm6, xmm2, 0xE4 ; move v to scratch psraw xmm6,2 ; divide v by 4 paddsw xmm3, xmm6 ; and add to r psraw xmm6,1 ; divide v by 2 paddsw xmm3, xmm6 ; and add to r psraw xmm6,2 ; divide v by 4 paddsw xmm3, xmm6 ; and add to r ; b = y + u + u >> 1 + u >> 2 + u >> 6 paddsw xmm5, xmm1 ; add u to b psraw xmm7,1 ; divide u by 2 paddsw xmm5, xmm7 ; and add to b psraw xmm7,1 ; divide u by 2 paddsw xmm5, xmm7 ; and add to b psraw xmm7,4 ; divide u by 32 paddsw xmm5, xmm7 ; and add to b ; g = y - u >> 2 - u >> 4 - u >> 5 - v >> 1 - v >> 3 - v >> 4 - v >> 5 movdqa xmm7,xmm2 ; move v to scratch pshufd xmm6,xmm1, 0xE4 ; move u to scratch movdqa xmm4,xmm0 ; g = y psraw xmm6,2 ; divide u by 4 psubsw xmm4,xmm6 ; subtract from g psraw xmm6,2 ; divide u by 4 psubsw xmm4,xmm6 ; subtract from g psraw xmm6,1 ; divide u by 2 psubsw xmm4,xmm6 ; subtract from g psraw xmm7,1 ; divide v by 2 psubsw xmm4,xmm7 ; subtract from g psraw xmm7,2 ; divide v by 4 psubsw xmm4,xmm7 ; subtract from g psraw xmm7,1 ; divide v by 2 psubsw xmm4,xmm7 ; subtract from g psraw xmm7,1 ; divide v by 2 psubsw xmm4,xmm7 ; subtract from g %endmacro ; outputer %macro rgba32sse2output 0 ; clamp values pxor xmm7,xmm7 packuswb xmm3,xmm7 ; clamp to 0,255 and pack R to 8 bit per pixel packuswb xmm4,xmm7 ; clamp to 0,255 and pack G to 8 bit per pixel packuswb xmm5,xmm7 ; clamp to 0,255 and pack B to 8 bit per pixel ; convert to bgra32 packed punpcklbw xmm5,xmm4 ; bgbgbgbgbgbgbgbg movdqa xmm0, xmm5 ; save bg values punpcklbw xmm3,xmm7 ; r0r0r0r0r0r0r0r0 punpcklwd xmm5,xmm3 ; lower half bgr0bgr0bgr0bgr0 punpckhwd xmm0,xmm3 ; upper half bgr0bgr0bgr0bgr0 ; write to output ptr movntdq [edi], xmm5 ; output first 4 pixels bypassing cache movntdq [edi+16], xmm0 ; output second 4 pixels bypassing cache %endmacro SECTION .data align=16 Const16 dw 16 dw 16 dw 16 dw 16 dw 16 dw 16 dw 16 dw 16 Const128 dw 128 dw 128 dw 128 dw 128 dw 128 dw 128 dw 128 dw 128 UMask db 0x01 db 0x80 db 0x01 db 0x80 db 0x05 db 0x80 db 0x05 db 0x80 db 0x09 db 0x80 db 0x09 db 0x80 db 0x0d db 0x80 db 0x0d db 0x80 VMask db 0x03 db 0x80 db 0x03 db 0x80 db 0x07 db 0x80 db 0x07 db 0x80 db 0x0b db 0x80 db 0x0b db 0x80 db 0x0f db 0x80 db 0x0f db 0x80 YMask db 0x00 db 0x80 db 0x02 db 0x80 db 0x04 db 0x80 db 0x06 db 0x80 db 0x08 db 0x80 db 0x0a db 0x80 db 0x0c db 0x80 db 0x0e db 0x80 ; void Convert_YUV422_RGBA32_SSSE3(void *fromPtr, void *toPtr, int width) width equ ebp+16 toPtr equ ebp+12 fromPtr equ ebp+8 ; void Convert_YUV420P_RGBA32_SSSE3(void *fromYPtr, void *fromUPtr, void *fromVPtr, void *toPtr, int width) width1 equ ebp+24 toPtr1 equ ebp+20 fromVPtr equ ebp+16 fromUPtr equ ebp+12 fromYPtr equ ebp+8 SECTION .text align=16 cglobal Convert_YUV422_RGBA32_SSSE3 ; reserve variables push ebp mov ebp, esp push edi push esi push ecx mov esi, [fromPtr] mov edi, [toPtr] mov ecx, [width] ; loop width / 8 times shr ecx,3 test ecx,ecx jng ENDLOOP REPEATLOOP: ; loop over width / 8 ; YUV422 packed inputer movdqa xmm0, [esi] ; should have yuyv yuyv yuyv yuyv pshufd xmm1, xmm0, 0xE4 ; copy to xmm1 movdqa xmm2, xmm0 ; copy to xmm2 ; extract both y giving y0y0 pshufb xmm0, [YMask] ; extract u and duplicate so each u in yuyv becomes u0u0 pshufb xmm1, [UMask] ; extract v and duplicate so each v in yuyv becomes v0v0 pshufb xmm2, [VMask] yuv2rgbsse2 rgba32sse2output ; endloop add edi,32 add esi,16 sub ecx, 1 ; apparently sub is better than dec jnz REPEATLOOP ENDLOOP: ; Cleanup pop ecx pop esi pop edi mov esp, ebp pop ebp ret cglobal Convert_YUV420P_RGBA32_SSSE3 ; reserve variables push ebp mov ebp, esp push edi push esi push ecx push eax push ebx mov esi, [fromYPtr] mov eax, [fromUPtr] mov ebx, [fromVPtr] mov edi, [toPtr1] mov ecx, [width1] ; loop width / 8 times shr ecx,3 test ecx,ecx jng ENDLOOP1 REPEATLOOP1: ; loop over width / 8 ; YUV420 Planar inputer movq xmm0, [esi] ; fetch 8 y values (8 bit) yyyyyyyy00000000 movd xmm1, [eax] ; fetch 4 u values (8 bit) uuuu000000000000 movd xmm2, [ebx] ; fetch 4 v values (8 bit) vvvv000000000000 ; extract y pxor xmm7,xmm7 ; 00000000000000000000000000000000 punpcklbw xmm0,xmm7 ; interleave xmm7 into xmm0 y0y0y0y0y0y0y0y0 ; extract u and duplicate so each becomes 0u0u punpcklbw xmm1,xmm7 ; interleave xmm7 into xmm1 u0u0u0u000000000 punpcklwd xmm1,xmm7 ; interleave again u000u000u000u000 pshuflw xmm1,xmm1, 0xA0 ; copy u values pshufhw xmm1,xmm1, 0xA0 ; to get u0u0 ; extract v punpcklbw xmm2,xmm7 ; interleave xmm7 into xmm1 v0v0v0v000000000 punpcklwd xmm2,xmm7 ; interleave again v000v000v000v000 pshuflw xmm2,xmm2, 0xA0 ; copy v values pshufhw xmm2,xmm2, 0xA0 ; to get v0v0 yuv2rgbsse2 rgba32sse2output ; endloop add edi,32 add esi,8 add eax,4 add ebx,4 sub ecx, 1 ; apparently sub is better than dec jnz REPEATLOOP1 ENDLOOP1: ; Cleanup pop ebx pop eax pop ecx pop esi pop edi mov esp, ebp pop ebp ret SECTION .note.GNU-stack noalloc noexec nowrite progbits

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  • some pointer to understanding GCC source code

    - by user299570
    hi, I'm student working on optimizing GCC for multi-core processor. I tried going through the source code, it is difficult to follow through it since I need to add some code to the back end. Can anyone suggest some good resource which explains the code flow through the different phases. Also suggest some development environment for debugging GCC mainly to step through the code. Is it possible on windows?

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  • Optimize MySQL query (ngrams, COUNT(), GROUP BY, ORDER BY)

    - by Gerardo
    I have a database with thousands of companies and their locations. I have implemented n-grams to optimize search. I am making one query to retrieve all the companies that match with the search query and another one to get a list with their locations and the number of companies in each location. The query I am trying to optimize is the latter. Maybe the problem is this: Every company ('anunciante') has a field ('estado') to make logical deletes. So, if 'estado' equals 1, the company should be retrieved. When I run the EXPLAIN command, it shows that it goes through almost 40k rows, when the actual result (the reality matching companies) are 80. How can I optimize this? This is my query (XXX represent the n-grams for the search query): SELECT provincias.provincia AS provincia, provincias.id, COUNT(*) AS cantidad FROM anunciantes JOIN anunciante_invertido AS a_i0 ON anunciantes.id = a_i0.id_anunciante JOIN indice_invertido AS indice0 ON a_i0.id_invertido = indice0.id LEFT OUTER JOIN domicilios ON anunciantes.id = domicilios.id_anunciante LEFT OUTER JOIN localidades ON domicilios.id_localidad = localidades.id LEFT OUTER JOIN provincias ON provincias.id = localidades.id_provincia WHERE anunciantes.estado = 1 AND indice0.id IN (SELECT invertido_ngrama.id_palabra FROM invertido_ngrama JOIN ngrama ON ngrama.id = invertido_ngrama.id_ngrama WHERE ngrama.ngrama = 'XXX') AND indice0.id IN (SELECT invertido_ngrama.id_palabra FROM invertido_ngrama JOIN ngrama ON ngrama.id = invertido_ngrama.id_ngrama WHERE ngrama.ngrama = 'XXX') AND indice0.id IN (SELECT invertido_ngrama.id_palabra FROM invertido_ngrama JOIN ngrama ON ngrama.id = invertido_ngrama.id_ngrama WHERE ngrama.ngrama = 'XXX') AND indice0.id IN (SELECT invertido_ngrama.id_palabra FROM invertido_ngrama JOIN ngrama ON ngrama.id = invertido_ngrama.id_ngrama WHERE ngrama.ngrama = 'XXX') AND indice0.id IN (SELECT invertido_ngrama.id_palabra FROM invertido_ngrama JOIN ngrama ON ngrama.id = invertido_ngrama.id_ngrama WHERE ngrama.ngrama = 'XXX') GROUP BY provincias.id ORDER BY cantidad DESC And this is the query explained (hope it can be read in this format): id select_type table type possible_keys key key_len ref rows Extra 1 PRIMARY anunciantes ref PRIMARY,estado estado 1 const 36669 Using index; Using temporary; Using filesort 1 PRIMARY domicilios ref id_anunciante id_anunciante 4 db84771_viaempresas.anunciantes.id 1 1 PRIMARY localidades eq_ref PRIMARY PRIMARY 4 db84771_viaempresas.domicilios.id_localidad 1 1 PRIMARY provincias eq_ref PRIMARY PRIMARY 4 db84771_viaempresas.localidades.id_provincia 1 1 PRIMARY a_i0 ref PRIMARY,id_anunciante,id_invertido PRIMARY 4 db84771_viaempresas.anunciantes.id 1 Using where; Using index 1 PRIMARY indice0 eq_ref PRIMARY PRIMARY 4 db84771_viaempresas.a_i0.id_invertido 1 Using index 6 DEPENDENT SUBQUERY ngrama const PRIMARY,ngrama ngrama 5 const 1 Using index 6 DEPENDENT SUBQUERY invertido_ngrama eq_ref PRIMARY,id_palabra,id_ngrama PRIMARY 8 func,const 1 Using index 5 DEPENDENT SUBQUERY ngrama const PRIMARY,ngrama ngrama 5 const 1 Using index 5 DEPENDENT SUBQUERY invertido_ngrama eq_ref PRIMARY,id_palabra,id_ngrama PRIMARY 8 func,const 1 Using index 4 DEPENDENT SUBQUERY ngrama const PRIMARY,ngrama ngrama 5 const 1 Using index 4 DEPENDENT SUBQUERY invertido_ngrama eq_ref PRIMARY,id_palabra,id_ngrama PRIMARY 8 func,const 1 Using index 3 DEPENDENT SUBQUERY ngrama const PRIMARY,ngrama ngrama 5 const 1 Using index 3 DEPENDENT SUBQUERY invertido_ngrama eq_ref PRIMARY,id_palabra,id_ngrama PRIMARY 8 func,const 1 Using index 2 DEPENDENT SUBQUERY ngrama const PRIMARY,ngrama ngrama 5 const 1 Using index 2 DEPENDENT SUBQUERY invertido_ngrama eq_ref PRIMARY,id_palabra,id_ngrama PRIMARY 8 func,const 1 Using index

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  • How to correctly cache images

    - by James Simpson
    I just installed Google's Page Speed plugin to Firebug, and everything looks good except for caching. I have set headers to cache my JS and CSS files, but it says the images aren't being cached. How can I make sure the images get cached for 30 days? These are static images, so I can't just add the headers with PHP like I did with the other files.

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  • How can i get rid of 'ORA-01489: result of string concatenation is too long' in this query?

    - by core_pro
    this query gets the dominating sets in a network. so for example given a network A<----->B B<----->C B<----->D C<----->E D<----->C D<----->E F<----->E it returns B,E B,F A,E but it doesn't work for large data because i'm using string methods in my result. i have been trying to remove the string methods and return a view or something but to no avail With t as (select 'A' as per1, 'B' as per2 from dual union all select 'B','C' from dual union all select 'B','D' from dual union all select 'C','B' from dual union all select 'C','E' from dual union all select 'D','C' from dual union all select 'D','E' from dual union all select 'E','C' from dual union all select 'E','D' from dual union all select 'F','E' from dual) ,t2 as (select distinct least(per1, per2) as per1, greatest(per1, per2) as per2 from t union select distinct greatest(per1, per2) as per1, least(per1, per2) as per1 from t) ,t3 as (select per1, per2, row_number() over (partition by per1 order by per2) as rn from t2) ,people as (select per, row_number() over (order by per) rn from (select distinct per1 as per from t union select distinct per2 from t) ) ,comb as (select sys_connect_by_path(per,',')||',' as p from people connect by rn > prior rn ) ,find as (select p, per2, count(*) over (partition by p) as cnt from ( select distinct comb.p, t3.per2 from comb, t3 where instr(comb.p, ','||t3.per1||',') > 0 or instr(comb.p, ','||t3.per2||',') > 0 ) ) ,rnk as (select p, rank() over (order by length(p)) as rnk from find where cnt = (select count(*) from people) order by rnk ) select distinct trim(',' from p) as p from rnk where rnk.rnk = 1`

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  • Optimizing sorting container of objects with heap-allocated buffers - how to avoid hard-copying buff

    - by Kache4
    I was making sure I knew how to do the op= and copy constructor correctly in order to sort() properly, so I wrote up a test case. After getting it to work, I realized that the op= was hard-copying all the data_. I figure if I wanted to sort a container with this structure (its elements have heap allocated char buffer arrays), it'd be faster to just swap the pointers around. Is there a way to do that? Would I have to write my own sort/swap function? #include <deque> //#include <string> //#include <utility> //#include <cstdlib> #include <cstring> #include <iostream> //#include <algorithm> // I use sort(), so why does this still compile when commented out? #include <boost/filesystem.hpp> #include <boost/foreach.hpp> using namespace std; namespace fs = boost::filesystem; class Page { public: // constructor Page(const char* path, const char* data, int size) : path_(fs::path(path)), size_(size), data_(new char[size]) { // cout << "Creating Page..." << endl; strncpy(data_, data, size); // cout << "done creating Page..." << endl; } // copy constructor Page(const Page& other) : path_(fs::path(other.path())), size_(other.size()), data_(new char[other.size()]) { // cout << "Copying Page..." << endl; strncpy(data_, other.data(), size_); // cout << "done copying Page..." << endl; } // destructor ~Page() { delete[] data_; } // accessors const fs::path& path() const { return path_; } const char* data() const { return data_; } int size() const { return size_; } // operators Page& operator = (const Page& other) { if (this == &other) return *this; char* newImage = new char[other.size()]; strncpy(newImage, other.data(), other.size()); delete[] data_; data_ = newImage; path_ = fs::path(other.path()); size_ = other.size(); return *this; } bool operator < (const Page& other) const { return path_ < other.path(); } private: fs::path path_; int size_; char* data_; }; class Book { public: Book(const char* path) : path_(fs::path(path)) { cout << "Creating Book..." << endl; cout << "pushing back #1" << endl; pages_.push_back(Page("image1.jpg", "firstImageData", 14)); cout << "pushing back #3" << endl; pages_.push_back(Page("image3.jpg", "thirdImageData", 14)); cout << "pushing back #2" << endl; pages_.push_back(Page("image2.jpg", "secondImageData", 15)); cout << "testing operator <" << endl; cout << pages_[0].path().string() << (pages_[0] < pages_[1]? " < " : " > ") << pages_[1].path().string() << endl; cout << pages_[1].path().string() << (pages_[1] < pages_[2]? " < " : " > ") << pages_[2].path().string() << endl; cout << pages_[0].path().string() << (pages_[0] < pages_[2]? " < " : " > ") << pages_[2].path().string() << endl; cout << "sorting" << endl; BOOST_FOREACH (Page p, pages_) cout << p.path().string() << endl; sort(pages_.begin(), pages_.end()); cout << "done sorting\n"; BOOST_FOREACH (Page p, pages_) cout << p.path().string() << endl; cout << "checking datas" << endl; BOOST_FOREACH (Page p, pages_) { char data[p.size() + 1]; strncpy((char*)&data, p.data(), p.size()); data[p.size()] = '\0'; cout << p.path().string() << " " << data << endl; } cout << "done Creating Book" << endl; } private: deque<Page> pages_; fs::path path_; }; int main() { Book* book = new Book("/some/path/"); }

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  • Most Efficient Alternative Method of Storing Settings for iPhone Apps

    - by JPK
    I am not using the Settings bundle to store the settings for my app, as I prefer to allow the user to access the settings within the app (they may be changed fairly often). I do realize that there is the option to do both, but for now, I am trying to find the most optimal place to store the settings within the app. I have a good number of settings (from what I have read, probably too many for NSUserDefaults), and the two main options I am considering are: 1) storing the settings in a dictionary in the plist, loading the settings into a NSDictionary property in the app delegate and accessing them via the sharedDelegate 2) storing the settings in a Core Data entity (1 row on Settings entity), loading the settings into a Settings object in the app delegate and accessing them via the sharedDelegate Of these two, which would be the optimal method, performance wise?

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  • Most flexible minimizer/compressor for ASP.NET MVC 2?

    - by AlexanderN
    From your experience, what's the most flexible minimizer/compressor (JS+CSS) for ASP.NET MVC you've dealt with? So far mbcompress doesn't seem to be too MVC friendly weboptimizer.codeplex.com lacks documentation clientdependency.codeplex.com is still in beta compress2 seems like a good candidate, but haven't tried it yet mvcscriptmanager only combines and compresses javascript but not CSS By flexible I mean Choose what should be compressed, minified, and combined Add exceptions. E.g. if debug don't compress XYZ.JS or don't minify ABC.CSS Caching In the end, it should help offer the best YSLOW score. If you know of any other assemblies out there, please list them also.

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  • Single Large v/s Multiple Small MySQL tables for storing Options

    - by Prasad
    Hi there, I'm aware of several question on this forum relating to this. But I'm not talking about splitting tables for the same entity (like user for example) Suppose I have a huge options table that stores list options like Gender, Marital Status, and many more domain specific groups with same structure. I plan to capture in a OPTIONS table. Another simple option is to have the field set as ENUM, but there are disadvantages of that as well. http://www.brandonsavage.net/why-you-should-replace-enum-with-something-else/ OPTIONS Table: option_id <will be referred instead of the name> name value group Query: select .. from options where group = '15' - Since this table is expected to be multi-tenant, the no of rows could grow drastically. - I believe splitting the tables instead of finding by the group would be easier to write & faster to execute. - or perhaps partitioning by the group or tenant? Pl suggest. Thanks

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  • Any difference between lazy loading Javascript files vs. placing just before </body>

    - by mhr
    Looked around, couldn't find this specific question discussed. Pretty sure the difference is negligible, just curious as to your thoughts. Scenario: All Javascript that doesn't need to be loaded before page render has been placed just before the closing </body> tag. Are there any benefits or detriments to lazy loading these instead through some Javascript code in the head that executes when the DOM load/ready event is fired? Let's say that this only concerns downloading one entire .js file full of functions and not lazy loading several individual files as needed upon usage. Hope that's clear, thanks.

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  • Better way to summarize data about stop times?

    - by Vimvq1987
    This question is close to this: http://stackoverflow.com/questions/2947963/find-the-period-of-over-speed Here's my table: Longtitude Latitude Velocity Time 102 401 40 2010-06-01 10:22:34.000 103 403 50 2010-06-01 10:40:00.000 104 405 0 2010-06-01 11:00:03.000 104 405 0 2010-06-01 11:10:05.000 105 406 35 2010-06-01 11:15:30.000 106 403 60 2010-06-01 11:20:00.000 108 404 70 2010-06-01 11:30:05.000 109 405 0 2010-06-01 11:35:00.000 109 405 0 2010-06-01 11:40:00.000 105 407 40 2010-06-01 11:50:00.000 104 406 30 2010-06-01 12:00:00.000 101 409 50 2010-06-01 12:05:30.000 104 405 0 2010-06-01 11:05:30.000 I want to summarize times when vehicle had stopped (velocity = 0), include: it had stopped since "when" to "when" in how much minutes, how many times it stopped and how much time it stopped. I wrote this query to do it: select longtitude, latitude, MIN(time), MAX(time), DATEDIFF(minute, MIN(Time), MAX(time)) as Timespan from table_1 where velocity = 0 group by longtitude,latitude select DATEDIFF(minute, MIN(Time), MAX(time)) as minute into #temp3 from table_1 where velocity = 0 group by longtitude,latitude select COUNT(*) as [number]from #temp select SUM(minute) as [totaltime] from #temp3 drop table #temp This query return: longtitude latitude (No column name) (No column name) Timespan 104 405 2010-06-01 11:00:03.000 2010-06-01 11:10:05.000 10 109 405 2010-06-01 11:35:00.000 2010-06-01 11:40:00.000 5 number 2 totaltime 15 You can see, it works fine, but I really don't like the #temp table. Is there anyway to query this without use a temp table? Thank you.

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  • Wrappers of primitive types in arraylist vs arrays

    - by ismail marmoush
    Hi, In "Core java 1" I've read CAUTION: An ArrayList is far less efficient than an int[] array because each value is separately wrapped inside an object. You would only want to use this construct for small collections when programmer convenience is more important than efficiency. But in my software I've already used Arraylist instead of normal arrays due to some requirements, though "The software is supposed to have high performance and after I've read the quoted text I started to panic!" one thing I can change is changing double variables to Double so as to prevent auto boxing and I don't know if that is worth it or not, in next sample algorithm public void multiply(final double val) { final int rows = getSize1(); final int cols = getSize2(); for (int i = 0; i < rows; i++) { for (int j = 0; j < cols; j++) { this.get(i).set(j, this.get(i).get(j) * val); } } } My question is does changing double to Double makes a difference ? or that's a micro optimizing that won't affect anything ? keep in mind I might be using large matrices.2nd Should I consider redesigning the whole program again ?

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  • Why is processing a sorted array faster than an unsorted array?

    - by GManNickG
    Here is a piece of code that shows some very peculiar performance. For some strange reason, sorting the data miraculously speeds up the code by almost 6x: #include <algorithm> #include <ctime> #include <iostream> int main() { // generate data const unsigned arraySize = 32768; int data[arraySize]; for (unsigned c = 0; c < arraySize; ++c) data[c] = std::rand() % 256; // !!! with this, the next loop runs faster std::sort(data, data + arraySize); // test clock_t start = clock(); long long sum = 0; for (unsigned i = 0; i < 100000; ++i) { // primary loop for (unsigned c = 0; c < arraySize; ++c) { if (data[c] >= 128) sum += data[c]; } } double elapsedTime = static_cast<double>(clock() - start) / CLOCKS_PER_SEC; std::cout << elapsedTime << std::endl; std::cout << "sum = " << sum << std::endl; } Without std::sort(data, data + arraySize);, the code runs in 11.54 seconds. With the sorted data, the code runs in 1.93 seconds. Initially I thought this might be just a language or compiler anomaly. So I tried it Java... import java.util.Arrays; import java.util.Random; public class Main { public static void main(String[] args) { // generate data int arraySize = 32768; int data[] = new int[arraySize]; Random rnd = new Random(0); for (int c = 0; c < arraySize; ++c) data[c] = rnd.nextInt() % 256; // !!! with this, the next loop runs faster Arrays.sort(data); // test long start = System.nanoTime(); long sum = 0; for (int i = 0; i < 100000; ++i) { // primary loop for (int c = 0; c < arraySize; ++c) { if (data[c] >= 128) sum += data[c]; } } System.out.println((System.nanoTime() - start) / 1000000000.0); System.out.println("sum = " + sum); } } with a similar but less extreme result. My first thought was that sorting brings the data into cache, but my next thought was how silly that is because the array was just generated. What is going on? Why is a sorted array faster than an unsorted array? The code is summing up some independent terms, the order should not matter.

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  • How to optimize this user ranking query

    - by James Simpson
    I have 2 databases (users, userRankings) for a system that needs to have rankings updated every 10 minutes. I use the following code to update these rankings which works fairly well, but there is still a full table scan involved which slows things down with a few hundred thousand users. mysql_query("TRUNCATE TABLE userRankings"); mysql_query("INSERT INTO userRankings (userid) SELECT id FROM users ORDER BY score DESC"); mysql_query("UPDATE users a, userRankings b SET a.rank = b.rank WHERE a.id = b.userid"); In the userRankings table, rank is the primary key and userid is an index. Both tables are MyISAM (I've wondered if it might be beneficial to make userRankings InnoDB).

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