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Select last row in MySQL
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I just ran this over 20m rows and it was very fast. I assume there's some kind of special case for handling this query. (EDIT: MySQL 5.7, InnoDB engine)
– Daniel Buckmaster
Oct 29 '18 at 2:20
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C++ valarray vs. vector
I like vectors a lot. They're nifty and fast. But I know this thing called a valarray exists. Why would I use a valarray instead of a vector? I know valarrays have some syntactic sugar, but other than that, when are they useful?
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How can I reconcile detached HEAD with master/origin?
...orce to the end of this command to push if the remote branch can not be “fast-forwarded” to the new commit (i.e. you dropped, or rewrote some existing commit, or otherwise rewrote some bit of history).
If you were in the middle of a rebase operation you should probably clean it up. You can chec...
Hide div after a few seconds
...1000 milliseconds).
setTimeout(function() {
$('#mydiv').fadeOut('fast');
}, 1000); // <-- time in milliseconds
#mydiv{
width: 100px;
height: 100px;
background: #000;
color: #fff;
text-align: center;
}
<script src="https://ajax.googleapis.com/ajax/libs/jqu...
Principal component analysis in Python
... U . d . Vt 1000 obs, p.obs( 20 vars ) = pc_obs( vars_pc( vars ))
fast approximate A . vars, using the `npc` principal components
Ut 2 pcs = p.obs_pc( 1000 obs )
V . dinv 20 vars = p.pc_vars( 2 principal vars )
V . dinv . Ut 20 vars, p.vars( 1000 obs ) = p...
Performance of Arrays vs. Lists
...ys for that extra tiny bit of micro-optimisation; arrays can be marginally faster if you use the indexer / for form - but IIRC believe it depends on the type of data in the array. But unless you need to micro-optimise, keep it simple and use List<T> etc.
Of course, this only applies if you ar...
Wrapping a C library in Python: C, Cython or ctypes?
...nd to specialise and tighten your loops algorithmically. And if you need a fast callback, just write a function with the appropriate signature and pass it into the C callback registry directly. Again, no overhead, and it gives you plain C calling performance. And in the much less likely case that yo...
Using a dictionary to count the items in a list [duplicate]
...ocations at a specific temperature or temperature range, while getting the fast insertions of a set.) Counter merely counts repetitions; distinct values are lost. That's much less useful--it's nothing more than a wrapped dict. I question calling that a multiset at all.
– Gle...
Best way to select random rows PostgreSQL
...bers (or use DISTINCT).
Join the ids to the big table. This should be very fast with the index in place.
Finally trim surplus ids that have not been eaten by dupes and gaps. Every row has a completely equal chance to be picked.
Short version
You can simplify this query. The CTE in the query above...
What is the most efficient way to deep clone an object in JavaScript?
...r, and hopefully will land in browsers. See this answer for more details.
Fast cloning with data loss - JSON.parse/stringify
If you do not use Dates, functions, undefined, Infinity, RegExps, Maps, Sets, Blobs, FileLists, ImageDatas, sparse Arrays, Typed Arrays or other complex types within your ob...