While all 3 properties make an element’s box seem invisible, there are crucial differences between them: Property Painted In layout Stacking context Pointer events Keyboard events opacity: 0; No Yes New Yes Yes visibility: hidden; No Yes Varies No No display: none; No No Varies No No The “Painted” column indicates if the browser will … Read more
I have looked for actual data for the past days, and found nothing. However, I did some research, which compares the cost of atomic ops with the costs of cache misses. The cost of the x86 LOCK prefix, (including lock cmpxchg for atomic CAS), before PentiumPro (as described in the doc), is a memory access … Read more
Frame pointer is a reference pointer allowing a debugger to know where local variable or an argument is at with a single constant offset. Although ESP’s value changes over the course of execution, EBP remains the same making it possible to reach the same variable at the same offset (such as first parameter will always … Read more
You can just as easily access each element in the list using e.g. path[[1]]. You can’t put a set of matrices into an atomic vector and access each element. A matrix is an atomic vector with dimension attributes. I would use the list structure returned by split, it’s what it was designed for. Each list … Read more
Loop unrolling makes sense if you can break dependency chains. This gives a out of order or super-scalar CPU the possibility to schedule things better and thus run faster. A simple example: for (int i=0; i<n; i++) { sum += data[i]; } Here the dependency chain of the arguments is very short. If you get … Read more
You can use list slicing to archive your goal. Remove the first 5 elements: n = 5 mylist = [1,2,3,4,5,6,7,8,9] newlist = mylist[n:] print newlist Outputs: [6, 7, 8, 9] Or del if you only want to use one list: n = 5 mylist = [1,2,3,4,5,6,7,8,9] del mylist[:n] print mylist Outputs: [6, 7, 8, 9]
I’ve a MySQL InnoDB table with 1000000 registers. Is this too much? No, 1,000,000 rows (AKA records) is not too much for a database. I ask because I noticed that some queries (for example, getting the last register of a table) are slower (seconds) in the table with 1 million registers than in one with … Read more
Your first approach (SQL query in the DB) is quite efficient because the DB knows how to perform a join. But it doesn’t really make sense to compare it with the other approaches, since they work directly in memory (Linq to DataSet) The query with multiple tables and a Where condition actually performs a cartesian … Read more
Yes, there is some compiler magic that optimises Option<ptr> to a single pointer (most of the time). use std::mem::size_of; macro_rules! show_size { (header) => ( println!(“{:<22} {:>4} {}”, “Type”, “T”, “Option<T>”); ); ($t:ty) => ( println!(“{:<22} {:4} {:4}”, stringify!($t), size_of::<$t>(), size_of::<Option<$t>>()) ) } fn main() { show_size!(header); show_size!(i32); show_size!(&i32); show_size!(Box<i32>); show_size!(&[i32]); show_size!(Vec<i32>); show_size!(Result<(), Box<i32>>); } … Read more
As per MSDN: The Stopwatch measures elapsed time by counting timer ticks in the underlying timer mechanism. If the installed hardware and operating system support a high-resolution performance counter, then the Stopwatch class uses that counter to measure elapsed time. Otherwise, the Stopwatch class uses the system timer to measure elapsed time. Use the Frequency … Read more