Algorithms for minimizing single-variable functions
algorithm,optimization,numerical-methods
For this setting, I'd go with Golden Section Search. Convexity implies unimodality, which is needed by this method. Conversely, this method does not need derivatives. You can find derivatives numerically, but that's another way of saying "multiple function assessments"; might as well use these for golden-section partitions. ...
How to write Max(L)<1 without using MAX func in MATLAB
every element of the vector L must be less than or equal to 1. This should be written as a set of constraints, not a single constraint. Artificially bundling the constraints L(1)<=1, L(2)<=1, ... into one constraint is just going to cause more pain to the solver. Example with...
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...
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...
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.
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...
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...
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...
How to make faster queries on my mysql table?
mysql,optimization,query-optimization
It is not possible to optimize a mixture of ASC and DESC, as in ORDER BY t.fecha DESC, t.idsensor ASC You tried a covering index: INDEX `sensor_temp` (`idsensor`,`fecha`,`temperatura`) However, this covering index may be better: INDEX `sensor_temp` (`fecha`,`idsensor`,`temperatura`) Then, if you are willing to get the sensors in a different...
How to efficiently select neighbour in 1-dimensional and n-dimensional space for Simulated Annealing
java,algorithm,search,optimization,simulated-annealing
So you are trying to find an n-dimensional point P' that is "randomly" near another n-dimensional point P; for example, at distance T. (Since this is simulated annealing, I assume that you will be decrementing T once in a while). This could work: double[] displacement(double t, int dimension, Random r)...
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...
Can this javascript code be cleaned up?
javascript,jquery,optimization
Rename f() to something else that makes more sense to your domain: var f = function(indicatorClicked, remainingIndicators) { $(indicatorClicked).toggleClass("icon-caret-up icon-caret-down"); $.each(remainingIndicators, function(index, indicator) { $(indicator).removeClass("icon-caret-up").addClass("icon-caret-down"); }); } $("#IDArea1").click(function () { f('#indicator1', ['#indicator2', '#indicator3']) }); $("#IDArea2").click(function () { f('#indicator2', ['#indicator1', '#indicator3']) }); $("#IDArea3").click(function () {...
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...
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...
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....
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)
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....
Getting the maximum sum of pairs' second elements given weight limitation on the first elements
java,algorithm,sorting,optimization
This is an instance of the Knapsack Problem. The Wikipedia page lists a lot of known algorithm that solve this efficiently. You might want to gather some inspiration from these algorithms.
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...
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...
Optimizing a large if-else branch with binary search
c,optimization,binary-search,linear-search
You should look at the generated instructions to see (gcc -S source.c), but generally it comes down to these three: 1) N is too small. If you only have a 8 different branches, you execute an average of 4 checks (assuming equally probable cases, otherwise it could be even faster)....
How configure Stanford QNMinimizer to get similar results as scipy.optimize.minimize L-BFGS-B
java,optimization,machine-learning,scipy,stanford-nlp
What you have should be just fine. (Have you actually had any problems with it?) Setting termination both on max iterations and max function evaluations is probably overkill, so you might omit the last argument to qn.minimize(), but it seems from the documentation that scipy does use both with a...
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...
How minimal can an SVG be?
Removing the viewBox creates a significant semantic difference as the SVG will no longer scale (i.e. be responsive to UA resizes). This only applies if you're viewing the image directly though if you're viewing it as a background-image or via a SVG <image> tag or html <img> tag then the...
