More efficient way to get nearest center
You should rather use the optimized cdist from scipy.spatial which is more efficient than calculating it with numpy, from scipy.spatial.distance import cdist dist = cdist(data, C, metric='euclidean') dist_idx = np.argmin(dist, axis=1) An even more elegant solution is to use scipy.spatial.cKDTree (as pointed out by @Saullo Castro in comments), which could...
SAS drop multiple variables indexed by tens
If the var<xx> variables are all multiples of ten, i.e. there are no other variables beginning with var, you can use the colon-operator, which acts as a wildcard, e.g. drop var: ; /* drop all variables beginning with 'var' */ Alternatively, you can dynamically generate a list of all the...
Picking Ad Mob Mediation Networks 2015
MillenialMedia - Pretty decent engineering. Pretty good revenue Inmobi - Good revenue. Sometimes really dodgy ads. I've experiemented with half a dozen others, but they provided insignificant revenue, or provided many bugs. But your mileage may vary....
Prefetching double class member requires casting to char*?
c++,performance,optimization,x86,prefetch
If you read the description for _mm_prefetch() from the site you linked to it has : void _mm_prefetch (char const* p, int i) Fetch the line of data from memory that contains address p to a location in the cache heirarchy specified by the locality hint i. So you need...
Mysql optimize to avoid table scan
mysql,sql,table,optimization,scan
You could try a self join like this: SELECT COUNT(DISTINCT sw1.word_id) FROM sentence_word sw1 JOIN sentence_word sw2 ON ( sw1.sent_id = sw2.sent_id AND sw2.word_id = [your word id] ) WHERE sw1.word_id != [your word id] or perhaps even better SELECT COUNT(DISTINCT sw1.word_id) FROM sentence_word sw1 JOIN sentence_word sw2 ON (...
OpenCV FAST corner detection SSE implementation walkthrough
c,performance,opencv,optimization,sse
As harold said, delta is used to make unsigned comparsion. Let's describe this implementation by steps: __m128i x0 = _mm_sub_epi8(_mm_loadu_si128((const __m128i*)(ptr + pixel[0])), delta); __m128i x1 = _mm_sub_epi8(_mm_loadu_si128((const __m128i*)(ptr + pixel[4])), delta); __m128i x2 = _mm_sub_epi8(_mm_loadu_si128((const __m128i*)(ptr + pixel[8])), delta); __m128i x3 = _mm_sub_epi8(_mm_loadu_si128((const __m128i*)(ptr + pixel[12])), delta); m0 =...
Which way of setting fields value is better and why?
Way 2 is better because it gives you a unified way of setting a variable value. But it brings in a risk, because you're calling an overrideable method in a constructor. So the right syntax is using the final keyword: public final void setField(int field){ this.field = field; } //way...
Why is Java faster if it repeats the same code?
java,optimization,jvm,jvm-hotspot
The fact that what you see is the result of some JIT optimization should be clear by now looking at all the comments you received. But what is really happening and why that code is optimized always nearly after the same amount of iterations of the outer for? I'll try...
In general, how expensive is calling an external program?
Like I said in my comment above, perhaps it would be best if you simply tried it and did some benchmarking. I'd expect this to depend primarily on the OS you're using. That being said, starting a new process generally is many orders of magnitude slower than calling a subroutine...
Why do we need to put the *.odex files under /system/app even if we already have /data/dalvik-cache?
android,optimization,virtual-machine,loader,dalvik
The /system/app directory is read-only on normal (non-developer) devices, and only updated when the system receives an update. The point of /system/app/*.odex is that the .odex file can be delivered as part of a system update, so it doesn't have to be generated on the first post-update boot, and doesn't...
Performing large queries on Array or DB in php? [closed]
php,mysql,arrays,performance,optimization
Database connections are going to be the most expensive part of the algorithm, so minimize the amount of time each connection will last. Pull it from the database and loop through the array. Unless you are doing a function that would be very quick in a database (ie- sorting on...
Efficiently transferring elements between arrays
javascript,arrays,optimization,memory-management,data-structures
splice is pretty harmful for performance in a loop. But you don't seem to need mutations on the input arrays anyway - you are creating new ones and overwrite the previous values. Just do function doTransfers() { var A_pending = []; var B2_pending = []; for (var i = 0;...
Matlab @fminunc objective function optimization
matlab,function,optimization,maximize
Both your functions return a vector of values whereas fminunc requires that the function returns a scalar / single value. The error is pretty clear. The function fminunc is trying to find the best solution that minimizes a cost function, so what you need to supply is a cost function....
Optimizing Ansible Transport\SSH for Unconventional Networks
networking,optimization,ssh,ansible
If you are working in a network where the connection might be lost 'during' execution of a play/task then I'm not sure if (read: I don't think) ansible saves the context of execution so often as to recover from such issues. If your network is bad, you should fix that....
code optimising for if-else function
Here is an answer. First remove all the branches and then implement as SSE. I haven't check the speed yet. const int T1 = 17560; const int T2 = 244583; const int SHIFT = 16; int A = 2*((dx ^ dy) >= 0)-1; //check (dy,dx) opposite sign dy = abs(dy);...
(Java) Efficiency in my Starter Bubble Sort
java,algorithm,optimization,foreach,bubble-sort
Using indexOf is not correct, if your ArrayList x contains more than one value of i, your sort method will behave incorrectly. For example, this case: [5, 5, 1] After running your program, return [5, 5, 1] Plus, using indexOf, as mentioned by tucuxi, will slow down your program....
Optimizing a simple linear curve (constant and coefficient estimated from a regression)
If the functions are linear, then they will be at a minimum at the lower end of the range where beta>=0, and at the upper end of the range if beta<=0 - no need to use optimize(). It's not entirely clear what you're expecting the code to do - if...
nuZ: What does the model say
There isn't much more to it. For soft constraints the number on the right of "|->" is given as follows. Suppose we assert (assert-soft F1 :weight w1 :id first) (assert-soft F2 :weight w2 :id first) (assert-soft F3 :weight w3 :id first) And suppose M is a model maximal assignment that...
(WHY?) Greatest+Coalesce way faster than a single select with or
(GREATEST and COALESCE are not relevant to the real question.) It may or may not be faster. Here's the logic... OR usually eliminates using an index. SELECT ... ORDER BY indexed_column LIMIT 1 may be able to use indexed_column to find the 1 row you want with no extra effort....
Alpha blending using table lookup is not as fast as expected
c,performance,optimization,alphablending,lookup-tables
Table lookup is not a panacea. It helps when the table is small enough, but in your case the table is very big. You write 16 megabytes used for the table is not an issue in this case which I think is very wrong, and is possibly the source of...
Minimize a function with two variables
There are a few problems with your overall process that cause trouble. First of all as @user227710 mentions in the comments you should replace && with &. These have different meanings. Now for the optimiser It looks like you want to set limits to your parameters (i.e. what is known...
Vary coefficient in system of equation in Matlab's fsolve
You can do it in one line using arrayfun, though it looks kind of convoluted and simply looping over p might be faster: function F = myfun(x,p) F = [p*x(1) - x(2) - exp(-x(1)); -x(1) + 2*x(2) - exp(-x(2))]; p_values = -3:.1:3; x = arrayfun(@(p)fsolve(@(x)myfun(x,p), x0), p_values, 'UniformOutput', false) and...
How can I efficiently create unique relationships in Neo4j?
If you want to create unique relationships you have 2 options: Prevent the path from being duplicated, using MERGE, just like @user2194039 suggested. I think this is the simplest, and best approach you can take. Turn your relationship into a node, and create an unique constraint on it. But it's...
What is the most efficient way to perform a multiplication?
Here is a JMH benchmark: @OutputTimeUnit(TimeUnit.SECONDS) @BenchmarkMode({ Mode.Throughput }) @Warmup(iterations = 10) @Fork(value = 1) @State(Scope.Benchmark) public class MyBenchmark { private static final double CONSTANT = 1.6712 * 1000 * 60; private double x = 0; @Benchmark public void testCaseOne() { for (double i = 1; i < 1000_000; i++)...
Disabling fp-model strict when using ifort with f2py
python,numpy,optimization,fortran,f2py
The flags -xhost -openmp -fp-model strict come from def get_flags_opt(self): return ['-xhost -openmp -fp-model strict'] in the file site-packages/numpy/distutils/fcompiler/intel.py for the classes that invoke ifort. You have two options to modify the behavior of these flags: call f2py with the --noopt flag to suppress these flags call f2py with the...
Speeding up a function involving mapply and integrate
r,optimization,integrate,mapply
You are performing a large number of independent integrations. You can speed things up by performing these integrations on separate cores simultaneously (if you have a multicore processor available). The problem is that R performs its calculations in a single threaded manner by default. However, there are a number packages...
How to improve performance method GetThumbnailAsync in window phone 8.1
c#,image-processing,optimization,winrt-xaml
You are currently awaiting file.GetThumbnailAsync for each file which means that although the function is executed asynchronously for each file, it is executed in order, not in parallel. Try converting each async operation returned from file.GetThumbnailAsyncto a Task and then storing those in a list and then await all tasks...
Delivery optimization with limits
Try looking at it as a bipartite graph, trying to maximize the flow: Order the distances between the cities and the labs from closest to farthest, then iterate over the list and: Move x samples from the city to the lab - where x=min(max_lab_capacity, number_of_samples). The edge between the city...
What is the advantage of the paperboat format in performance optimization of ML?
optimization,machine-learning,dataset
I don't know if this format really provides better representation, but I can speculate why it can be more efficient. First, as they state at format description, "Having data of the same precision consecutive enables hardware vectorization."; consider also wikipedia: "Vector processing techniques have since been added to almost all...
How to interpret the output of the CPLEX interactive optimizer?
The % gap is the relative difference between the best solution and the best known bound for a solution. This is guaranteed to be higher than the gap between the best known solution and the true global optimum. In your case, the best bound is 83.9275, the best bound is...
nuZ: Use of soft-assertions with weights and ids
By default Z3 solves the objectives one at a time and finds the lexicographically best solution. First it tries to satisfy as many soft constraints from "first". The weight you associate with the soft constraints is a penalty for not satisfying the constraint. That is, it is not an award,...
Perform integer division using multiplication
assembly,optimization,bit-manipulation,division,multiplication
That method is called, "Division by Invariant Multiplication". The constants that you're seeing are actually approximates of the reciprocal. So rather than computing: N / D = Q you do something like this instead: N * (1/D) = Q where 1/D is a reciprocal that can be precomputed. Fundamentally, reciprocals...
Optimizing for Social Leaderboards
python,google-app-engine,optimization,twitter,leaderboard
I would organize the task like this: Make an asynchronous fetch call to the Twitter feed Use memcache to hold all the AuthAccount->User data: Request the data from memcache, if it doesn't exist then make a fetch_async() call to the AuthAccount to populate memcache and a local dict Run each...
Does compiler optimize operation on const variable and literal const number?
You have some good answers already that answer your factual question: No, the C# compiler does not generate the code to do a single multiplication by 86. It generates a multiplication by 43 and a multiplication by 2. There are some subtleties here that no one has gone into though....
How can I extract part of a PChar into a string?
string,delphi,optimization,pchar
Let's consider the corner cases. I think they are: AInput invalid. AStart < 1. AStart > FLength. ASubstringLength < 0. ASubstringLength + (AStart-1) > FLength. We can ignore case 1 in my opinion. The onus should be on the caller to provide a valid PChar. Indeed your check that AInput...
R: NaNs produced in Log-Likelihood optimisation
Optim converges with your initial parameters, so I'm not sure there is a problem. But, you can also try using the alternative optimization routines and run a simple test to see what parameters are giving warnings ## Test results with other methods x1 <- optim(c(17,5,3,4,27,13),LL,method="BFGS",u=u) ps <- x1$par x2 <-...
Optimization: memcached vs mysql memory
So, memcached is better and faster! BUT: memcached can remove old keys, if ttl expires or small size for sets other keys. The situation may be: In first request you set key-value to memcached. In second request (parallel) you set another key value to memcached, and in memcached small memory...
Is there a more efficient way to solve this?
python,python-2.7,optimization,matrix
In terms of refactoring, you almost certainly want to avoid "brute force" in the sense of having to explicitly type out all your cases :) @alexmcf addresses this above. In conceptual terms, your approach follows the problem statement directly: check all neighbors for each number in the matrix and sum...
FastDOM - Read / write every 17ms?
javascript,dom,optimization,asynchronous,requestanimationframe
Both types of DOM operations (read/write) have their own job queues. Each queue is flushed (e.g. all jobs in it are ran/executed) every requestAnimationFrame If you add 100 read operations all within 5ms, for example, (during a loop for instance), all of those read operations will (most likely) occur the...
optimization algorithm for circular data
r,optimization,circular,maximization
I would compute all the pairs of rows in df: (pairs <- cbind(1:nrow(df), c(2:nrow(df), 1))) # [,1] [,2] # [1,] 1 2 # [2,] 2 3 # [3,] 3 4 # [4,] 4 5 # [5,] 5 6 # [6,] 6 1 You can find the best pairing with which.max:...
Placing Limits on Optim
r,optimization,regression,rscript
This seems to work fine: opt1 <- optim(startparam, fn=ls,method="L-BFGS-B", Val=Val,Hi=Hi,Di=Di, lower =c(20,10,0), upper =c(100,70,25)) note that the values of Val, Hi, Di get passed through optim to the objective function....
glclearcolor best color?
No (technically there could be a difference, since OpenGL does not impose any performance requirements on the functioncall). Btw. you should set the clear color before calling clear....
Compiling SCIP: 'spxsolver.h' file not found
The problem was that I was installing the scip-3.1.1.tgz rather than scipoptsuite-3.1.1.tgz. Running make on scipoptsuite-3.1.1.tgz runs perfectly fine.
Loop unrolling in inlined functions in C
Well, obviously the compiler isn't 'smart' enough to propagate the n constant and unroll the for loop. Actually it plays it safe since arg->n can change between instantiation and usage. In order to have consistent performance across compiler generations and squeeze the maximum out of your code, do the unrolling...
How to load all symbols from shared library on start up?
c,linux,optimization,shared-libraries,glibc
Setting the environment variable LD_BIND_NOW should help achieving just that. Set it with export LD_BIND_NOW=1 then execute your program. Excerpt: ELF platforms (Linux, Solaris, FreeBSD, HP-UX, IRIX, etc.) support lazy binding of procedure addresses, which is an optimization that yields better performance overall but a genuine problem for applications that...
Better to declare JavaScript Object inside for loop or outside in terms of time optimization
javascript,arrays,optimization,variable-declaration
Both are the same. for loops don't create a new scope so the variables are hoisted to the top of the containing function scope. ex: > i undefined > for (var i = 0; i < 5; i++) { var test = i; } undefined > i 5 > test...
Inline function at -O0 causes link failure in clang [duplicate]
c,optimization,clang,inline,c99
At -O1 and greater it is not calling the function it just moves the code into main, we can see this by using godbolt which shows the asm as follows see it live: main: # @main pushq %rax movl $.L.str, %edi movl $42, %esi xorl %eax, %eax callq printf xorl...
weird optimization (remove a function) in GCC
This code causes undefined behaviour: uint32_t *p = (uint32_t *)vector; uint32_t tmp = p[0]; The memory pointed to by vector is an object of type uint64_t , however you read it via an lvalue of type uint32_t. This violates the strict aliasing rule. Since your program always calls this function,...
Does LINQ make use of underlying data structure?
They do where it makes sense, typically not for the actual type but for an interface (for example they check for IList when it helps speedup)
Better way to check if subdomain exists without using database query or hosts file
php,apache,symfony2,optimization,wildcard-subdomain
You could cache all each of the subdomain requests (using something like Doctrine cache as a wrapper for whatever caching system you use) so that each subsequent check would only need to check the cache rather than the database. Also when adding/removing/updating your subdomain object you could update the cache...
Optimization Toolbox (fmincon) - How to set logical constraints?
What you are looking for are nonlinear constraints, fmincon can handle it (I only know the command, not the GUI) with the argument nonlcon. For more information look at this guide http://de.mathworks.com/help/optim/ug/fmincon.html How would you implement this? First create a function function [c, ceq] = mycondition(x) c = -max(x)/min(x)/10; ceq...
Fair timing of two equivalent functions with -O3
Create a variable dummy and initialize it to argc. Then in each loop increment dummy by the return of the function. Then return dummy. This should stop the compiler from eliding the function calls.
type conversion performance optimizable?
c#,xml,csv,optimization,type-conversion
IEnumerable<string> values = new List<string>(); values = … Probably not going to be a big deal, but why create a new List<string>() just to throw it away. Replace this with either: IEnumerable<string> values; values = … If you need values defined in a previous scope, or else just: Enumerable<string> values...
HackerEarth Probelm: Reverse Primes
java,optimization,out-of-memory,primes
There are two possibilities: You use -Xmx256M which means a 256 MB heap. But there's more than just the heap and your VM may get killed when it tries to get more. You give 256 MB to your VM but your program needs more and gets killed. <---- As RealSkeptic...
Add a python flag cx_freeze to executable
python,optimization,distribution,cx-freeze,pyglet
You can use the same -O flag when you run cx_freeze to generate your final build, meaning that the cx_freeze generated bytecode will already be optimized. From the cxfreeze docs: cxfreeze hello.py --target-dir dist Further customization can be done using the following options: ... -O optimize generated bytecode as per...
Optimizing a sub-sub-query in MySQL
If you want only the most recent comment for a given user, then you can express this as: SELECT rc.* FROM requests r JOIN requests_comments rc ON rc.request_id = r.id WHERE r.username = 'someuser' ORDER BY rc.commented_at DEC LIMIT 1; For performance, you want an index on requests(username, id) and...
Disable JRockit Optimzation per class
optimization,jvm-hotspot,jrockit
You can create an opt file, see JRockit R28: http://docs.oracle.com/cd/E15289_01/doc.40/e15059/crash.htm#BABJGICB Earlier releases: https://docs.oracle.com/cd/E13150_01/jrockit_jvm/jrockit/geninfo/diagnos/crash.html#wp1010461...
How to shorten `if-statement`
Store all elements in single dimension array first, in your case this will be look like: $array = array('a','b','c','d','e','f'); Then use php in built function in_array() to check whether $col exists in array, in your this looks like: in_array($col, $array); Entire code: $array = array('a','b','c','d','e','f'); if(in_array($col, $array)) { continue; }...
CSSRules group selectors with common properties
javascript,jquery,html,css,optimization
This looks great, and I have only a minor suggestion. Change your code as follows: for (j = 0; rule = rules[j]; j++) { var styles = rule.style, style, k; var elements = document.querySelectorAll(rule.selectorText); if(elements.length) { for(k = 0; style = styles[k]; k++) { ... } console.log(rule.cssText); } } This...
make all elements in list equal with minimal cost
Determinstic variant First a more efficient but deterministic approach: occurs_most([],_,0). occurs_most(List,X,Nr) :- msort(List,[H|T]), most_sort(T,H,1,H,1,X,Nr). most_sort([Hb|T],Ha,Na,Hb,Nb,Hr,Nr) :- !, Nb1 is Nb+1, most_sort(T,Ha,Na,Hb,Nb1,Hr,Nr). most_sort([Hc|T],_,Na,Hb,Nb,Hr,Nr) :- Nb > Na, !, most_sort(T,Hb,Nb,Hc,1,Hr,Nr). most_sort([Hc|T],Ha,Na,_,_,Hr,Nr) :- most_sort(T,Ha,Na,Hc,1,Hr,Nr). most_sort([],Ha,Na,_,Nb,Ha,Na) :- Na >= Nb, !. most_sort([],_,_,Hb,Nb,Hb,Nb). First you use msort/2 to sort the list. Then you iterate over...