Occassionally I need to check for duplicate IDs in a set of values and generally I use a Dictionary for this - using just the keys and leaving values empty. Note that this is tight and highly optimized code so please no cries of 'premature optimization'! Assuming scenarios where CPU and RAM are being squeezed to the limit I was wanting...
I have 4 DIV that I want to have a scroll event fired when you scroll on one of those div's. This is the code below. $('#div1, #div2, #div3, #div4').scroll(function() { alert('...'); }); In Firefox/Chrome, this runs fast; however, in Internet Explorer this runs so slow that it actually prevents me from scrolling the div. I'm usin...
What is the best solution for getting the base 2 logarithm of a number that I know is a power of two (2^k). (Of course I know only the value 2^k not k itself.) One way I thought of doing is by subtracting 1 and then doing a bitcount: lg2(n) = bitcount( n - 1 ) = k, iff k is an integer 0b10000 - 1 = 0b01111, bitcount(0b01111) = 4 But ...
What is the fastest way to find if a number is even or odd? ...
I've been trying to optimize some extremely performance-critical code (a quick sort algorithm that's being called millions and millions of times inside a monte carlo simulation) by loop unrolling. Here's the inner loop I'm trying to speed up: // Search for elements to swap. while(myArray[++index1] < pivot) {} while(pivot < myArray[--in...
I wrote two methods to check there performance public class Test1 { private String value; public void notNull(){ if( value != null) { //do something } } public void nullNot(){ if( null != value) { //do something } } } and checked it's byte code after compiling public void notNull(); Code: Stack=1, Locals=1, Args_si...
Hi, I am trying to optimize my program. I think I understand the basics of closure. I am confused about the scope chain though. I know that in general you want a low scope (to access variables quickly). Say I have the following object: var my_object = (function(){ //private variables var a_private = 0; return{ //...
I am new to Java, so I am not aware of the nitty gritties. Why can't I create generic array of parametrized ArrayList? Instead I have to write, ArrayList<String>[] alist = new ArrayList[10]; or I have to create List of ArrayLists. Aren't arrays supposed to be more efficient than ArrayLists? Then why doesn't Java allow it? Also, wha...
Is it recommended to count in small loops (where possible) down from length - 1 to zero instead of counting up to length - 1? 1.) Counting down for (int i = a.length - 1; i >= 0; i--) { if (a[i] == key) return i; } 2.) Counting up for (int i = 0; i < a.length; i++) { if (a[i] == key) return i; } The first one is slightly f...
In another question, the accepted answer suggested replacing a (very cheap) if statement in Python code with a try/except block to improve performance. Coding style issues aside, and assuming that the exception is never triggered, how much difference does it make (performance-wise) to have an exception handler, versus not having one, ve...
Say you see a loop like this one: for(int i=0; i<thing.getParent().getObjectModel().getElements(SOME_TYPE).count(); ++i) { thing.getData().insert( thing.GetData().Count(), thing.getParent().getObjectModel().getElements(SOME_TYPE)[i].getName() ); } if this was Java I'd probably not think twice. But in performance-...
I'm using google page speed and it's telling me my css is inefficient... Very inefficient rules (good to fix on any page): * table.fancy thead td Tag key with 2 descendant selectors and Class overly qualified with tag * table.fancy tfoot td Tag key with 2 descendant selectors and Class overly qualified with tag The css rules ar...
The questions are in bold, for those that cannot be bothered reading a question in depth. This is a followup to this question. It is to do with the initialization semantics of static variables in functions. Static variables should be initialized once, and their internal state might be altered later - as I (currently) do in the linked qu...
Let say I have a switch statement as below switch(alphabet) { case "f": //do something break; case "c": //do something break; case "a": //do something break; case "e": //do something break; } Now suppose I know that the frequency of having Alphabet e...
I'm writing a performance-critical, number-crunching C++ project where 70% of the time is used by the 200 line core module. I'd like to optimize the core using inline assembly, but I'm completely new to this. I do, however, know some x86 assembly languages including the one used by GCC and NASM. All I know: I have to put the assemble...
I'm writing something performance-critical and wanted to know if it could make a difference if I use: int test( int a, int b, int c ) { // Do millions of calculations with a, b, c } or class myStorage { public: int a, b, c; }; int test( myStorage values ) { // Do millions of calculations with values.a, values.b, values.c } ...
In C language, Why does n++ execute faster than n=n+1? (int n=...; n++;) (int n=...; n=n+1;) Our instructor asked that question in today's class. (this is not homework) ...
Hello! Given the arrays: int canvas[10][10]; int addon[10][10]; Where all the values range from 0 - 100, what is the fastest way in C++ to add those two arrays so each cell in canvas equals itself plus the corresponding cell value in addon? IE, I want to achieve something like: canvas += another; So if canvas[0][0] =3 and addon[0...
Dear SO: I have a simple importer, it goes through each line of a rather big csv and imports it to the database. My question is: Should I call another method to insert each object (generating a DO and telling it's mapper to insert) or should I hardcode the insert process in the import method, duplicating the code? I know the elegant th...
Hello all, I am trying to make a Java port of a simple feed-forward neural network. This obviously involves lots of numeric calculations, so I am trying to optimize my central loop as much as possible. The results should be correct within the limits of the float data type. My current code looks as follows (error handling & initializati...