This is caused by the nature of deferred expressions #{} (note that “legacy” standard expressions ${} behave exactly the same when Facelets is used instead of JSP). The deferred expression is not immediately evaluated, but created as a ValueExpression object and the getter method behind the expression is executed everytime when the code calls ValueExpression#getValue(). … Read more
There are several optimizations a compiler can make on a switch. I don’t think the oft-mentioned “jump-table” is a very useful one though, as it only works when the input can be bounded some way. C Pseudocode for a “jump table” would be something like this — note that the compiler in practice would need … Read more
Try this: sys.getsizeof(object) getsizeof() Return the size of an object in bytes. It calls the object’s __sizeof__ method and adds an additional garbage collector overhead if the object is managed by the garbage collector. A recursive recipe
This did the job (in the year 2012): #include <stdio.h> const unsigned long long size = 8ULL*1024ULL*1024ULL; unsigned long long a[size]; int main() { FILE* pFile; pFile = fopen(“file.binary”, “wb”); for (unsigned long long j = 0; j < 1024; ++j){ //Some calculations to fill a[] fwrite(a, 1, size*sizeof(unsigned long long), pFile); } fclose(pFile); return … Read more
Linux uses a 1-1 threading model, with (to the kernel) no distinction between processes and threads — everything is simply a runnable task. * On Linux, the system call clone clones a task, with a configurable level of sharing, among which are: CLONE_FILES: share the same file descriptor table (instead of creating a copy) CLONE_PARENT: … Read more
As I mentioned to David Wolever, there’s more to this than meets the eye; both methods dispatch to is; you can prove this by doing min(Timer(“x == x”, setup=”x = ‘a’ * 1000000″).repeat(10, 10000)) #>>> 0.00045456900261342525 min(Timer(“x == y”, setup=”x = ‘a’ * 1000000; y = ‘a’ * 1000000″).repeat(10, 10000)) #>>> 0.5256857610074803 The first can … Read more
As far as I can tell, both syntaxes are equivalent. The first is SQL standard, the second is MySQL’s extension. So they should be exactly equivalent performance wise. http://dev.mysql.com/doc/refman/5.6/en/insert.html says: INSERT inserts new rows into an existing table. The INSERT … VALUES and INSERT … SET forms of the statement insert rows based on explicitly … Read more
The most common thing that will make a query non-sargable is to include a field inside a function in the where clause: SELECT … FROM … WHERE Year(myDate) = 2008 The SQL optimizer can’t use an index on myDate, even if one exists. It will literally have to evaluate this function for every row of … Read more
As pointed out by the other answer, because the case values are contiguous (as opposed to sparse), the generated bytecode for your various tests uses a switch table (bytecode instruction tableswitch). However, once the JIT starts its job and compiles the bytecode into assembly, the tableswitch instruction does not always result in an array of … Read more
No! The same execution plan, look at these two tables: CREATE TABLE table1 ( id INT, name VARCHAR(20) ); CREATE TABLE table2 ( id INT, name VARCHAR(20) ); The execution plan for the query using the inner join: — with inner join EXPLAIN PLAN FOR SELECT * FROM table1 t1 INNER JOIN table2 t2 ON … Read more