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What's the fastest way to merge/join data.frames in R?
...ata.table is actually timing base functions colMeans and cbind (the memory allocation and copying induced by using those functions). There are good and bad ways of using data.table, too.
benchmark(replications = 1, order = "elapsed",
aggregate = aggregate(d[c("x", "y")], d[c("g1", "g2")], mean),...
How are strings passed in .NET?
... Each instance is immutable. When you change the value of a string you are allocating a new string in memory.
So only the reference is passed to your function, but when the string is edited it becomes a new instance and doesn't modify the old instance.
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JavaScript hashmap equivalent
...ou can control indexing done by JavaScript without heavy lifting of memory allocation, and overflow handling.
Of course, if you truly want the "industrial-grade solution", you can build a class parameterized by the key function, and with all the necessary API of the container, but … we use JavaScr...
What is the meaning of “non temporal” memory accesses in x86
...Policies and Performance, they can be considered as write-around (no-write-allocate, no-fetch-on-write-miss).
Finally, it may be interesting to review John McAlpin notes about non-temporal stores.
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How to pass parameters correctly?
...mally by copying the object (**)
(*) pointers may refers to dynamically allocated memory, therefore when possible you should prefer references over pointers even if references are, in the end, usually implemented as pointers.
(**) "normally" means by copy constructor (if you pass an object of th...
Convert a series of parent-child relationships into a hierarchical tree?
...verhead on parsing recursive functions/calls. If there's no explicit stack allocation, I'd take iteration over recursion every day.
– user719662
Sep 17 '18 at 8:41
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Please explain the exec() function and its family
... for the child and all the data would have been copied to child’s pages. Allocating new memory and copying data is a very expensive process(takes processor’s time and other system resources). We also know that in most cases, the child is going to call exec() and that would replace the child’s ...
Heap vs Binary Search Tree (BST)
...le its size takes O(n) worst case, while the tree heap just does new small allocations for each node.
Still, the backing array doubling is O(1) amortized, so it comes down to a maximum latency consideration. Mentioned here.
Philosophy
BSTs maintain a global property between a parent and all desc...
What's “P=NP?”, and why is it such a famous question? [closed]
...On the other hand, there's whole classes of planning problems and resource allocation problems that we could solve effectively.
You may have heard the description NP-complete. An NP-complete problem is one that is NP (of course), and has this interesting property: if it is in P, every NP problem ...
How efficient is locking an unlocked mutex? What is the cost of a mutex?
...you wish. You are only limited by the amount of memory you application can allocate.
Summary. User-space locks (and the mutexes in particular) are cheap and not subjected to any system limit. But too many of them spells nightmare for debugging. Simple table:
Less locks means more contentions (slo...