大约有 44,000 项符合查询结果（耗时：0.0763秒） [XML]
Does async(launch::async) in C++11 make thread pools obsolete for avoiding expensive thread creation
...rong. I was under the impression that Linux thread creation was very cheap and after testing I determined that the overhead of function call in a new thread vs. a normal one is enormous. The overhead for creating a thread to handle a function call is something like 10000 or more times slower than a ...
mongodb count num of distinct values per field/key
...
MongoDB has a distinct command which returns an array of distinct values for a field; you can check the length of the array for a count.
There is a shell db.collection.distinct() helper as well:
> db.countries.distinct('country');
[ "Spain", "Engl...
subtle differences between JavaScript and Lua [closed]
...oesn't convert between types for any comparison operators. In JS, only === and !== don't type juggle.
Lua has an exponentiation operator (^); JS doesn't. JS uses different operators, including the ternary conditional operator (?: vs and/or), and, as of 5.3, bitwise operators (&, |, etc. vs. meta...
How to make jQuery to not round value returned by .width()?
I've searched around and couldn't find this. I'm trying to get the width of a div, but if it has a decimal point it rounds the number.
...
How to give System property to my test via Gradle and -D
...
The -P flag is for gradle properties, and the -D flag is for JVM properties. Because the test may be forked in a new JVM, the -D argument passed to gradle will not be propagated to the test - it sounds like that is the behavior you are seeing.
You can use the sy...
Why do you need to create a cursor when querying a sqlite database?
I'm completely new to Python's sqlite3 module (and SQL in general for that matter), and this just completely stumps me. The abundant lack of descriptions of cursor objects (rather, their necessity) also seems odd.
...
Difference between int32, int, int32_t, int8 and int8_t
... in a C program recently. I know that it stores 32 bits, but don't int and int32 do the same?
3 Answers
...
Applying a git post-commit hook to all current and future repos
I've written a Git post-commit hook and it works correctly. However, I want to add this hook to apply to all current (and future) git repositories I am working on. I tried adding the hook to my ~/.git/hooks/ instead of in the hooks directory in the project directory, however, this did not seem t...
Objective-C implicit conversion loses integer precision 'NSUInteger' (aka 'unsigned long') to 'int'
I'm working through some exercises and have got a warning that states:
4 Answers
4
...
Linq to SQL how to do “where [column] in (list of values)”
I have a function where I get a list of ids, and I need to return the a list matching a description that is associated with the id. E.g.:
...