people | simple HTTP/JSON API | JSON Processing library
kandi X-RAY | people Summary
kandi X-RAY | people Summary
People requires Go version >= 1.5 with GO15VENDOREXPERIMENT=1. As of Go 1.6 the vendor experiment is enabled by default. Run go get -u github.com/albrow/people, which will automatically install the source code into the correct location at $GOPATH/src/github.com/albrow/people. To start the server, change into the project root directory and run go run main.go. The server runs on port 3000.
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Top functions reviewed by kandi - BETA
- Update a person
- Main is the main function .
- init will initialize the People Pool
- ClosePool closes the pool
people Key Features
people Examples and Code Snippets
Community Discussions
Trending Discussions on people
QUESTION
While testing things around Compiler Explorer, I tried out the following overflow-free function for calculating average of 2 unsigned 32-bit integer:
...ANSWER
Answered 2022-Mar-08 at 10:00Clang does the same thing. Probably for compiler-construction and CPU architecture reasons:
Disentangling that logic into just a swap may allow better optimization in some cases; definitely something it makes sense for a compiler to do early so it can follow values through the swap.
Xor-swap is total garbage for swapping registers, the only advantage being that it doesn't need a temporary. But
xchg reg,reg
already does that better.
I'm not surprised that GCC's optimizer recognizes the xor-swap pattern and disentangles it to follow the original values. In general, this makes constant-propagation and value-range optimizations possible through swaps, especially for cases where the swap wasn't conditional on the values of the vars being swapped. This pattern-recognition probably happens soon after transforming the program logic to GIMPLE (SSA) representation, so at that point it will forget that the original source ever used an xor swap, and not think about emitting asm that way.
Hopefully sometimes that lets it then optimize down to only a single mov
, or two mov
s, depending on register allocation for the surrounding code (e.g. if one of the vars can move to a new register, instead of having to end up back in the original locations). And whether both variables are actually used later, or only one. Or if it can fully disentangle an unconditional swap, maybe no mov
instructions.
But worst case, three mov
instructions needing a temporary register is still better, unless it's running out of registers. I'd guess GCC is not smart enough to use xchg reg,reg
instead of spilling something else or saving/restoring another tmp reg, so there might be corner cases where this optimization actually hurts.
(Apparently GCC -Os
does have a peephole optimization to use xchg reg,reg
instead of 3x mov: PR 92549 was fixed for GCC10. It looks for that quite late, during RTL -> assembly. And yes, it works here: turning your xor-swap into an xchg: https://godbolt.org/z/zs969xh47)
with no memory reads, and the same number of instructions, I don't see any bad impacts and feels odd that it be changed. Clearly there is something I did not think through though, but what is it?
Instruction count is only a rough proxy for one of three things that are relevant for perf analysis: front-end uops, latency, and back-end execution ports. (And machine-code size in bytes: x86 machine-code instructions are variable-length.)
It's the same size in machine-code bytes, and same number of front-end uops, but the critical-path latency is worse: 3 cycles from input a
to output a
for xor-swap, and 2 from input b
to output a
, for example.
MOV-swap has at worst 1-cycle and 2-cycle latencies from inputs to outputs, or less with mov-elimination. (Which can also avoid using back-end execution ports, especially relevant for CPUs like IvyBridge and Tiger Lake with a front-end wider than the number of integer ALU ports. And Ice Lake, except Intel disabled mov-elimination on it as an erratum workaround; not sure if it's re-enabled for Tiger Lake or not.)
Also related:
- Why is XCHG reg, reg a 3 micro-op instruction on modern Intel architectures? - and those 3 uops can't benefit from mov-elimination. But on modern AMD
xchg reg,reg
is only 2 uops.
GCC's real missed optimization here (even with -O3
) is that tail-duplication results in about the same static code size, just a couple extra bytes since these are mostly 2-byte instructions. The big win is that the a
path then becomes the same length as the other, instead of twice as long to first do a swap and then run the same 3 uops for averaging.
update: GCC will do this for you with -ftracer
(https://godbolt.org/z/es7a3bEPv), optimizing away the swap. (That's only enabled manually or as part of -fprofile-use
, not at -O3
, so it's probably not a good idea to use all the time without PGO, potentially bloating machine code in cold functions / code-paths.)
Doing it manually in the source (Godbolt):
QUESTION
I am wondering how to solve this problem with basic Python (no libraries to be used): How to calculate when one's 10000 day after their birthday will be (/would be). For instance, given Monday 19/05/2008 the desired day is Friday 05/10/2035 (according to https://www.durrans.com/projects/calc/10000/index.html?dob=19%2F5%2F2008&e=mc2)
What I have done so far is the following script:
...ANSWER
Answered 2022-Mar-06 at 18:02Using base python packages only
On the basis that "no special packages" means you can only use base python packages, you can use datetime.timedelta
for this type of problem:
QUESTION
Haskell typeclasses often come with laws; for instance, instances of Monoid
are expected to observe that x <> mempty = mempty <> x = x
.
Typeclass laws are often written with single-equals (=
) rather than double-equals (==
). This suggests that the notion of equality used in typeclass laws is something other than that of Eq
(which makes sense, since Eq
is not a superclass of Monoid
)
Searching around, I was unable to find any authoritative statement on the meaning of =
in typeclass laws. For instance:
- The Haskell 2010 report does not even contain the word "law" in it
- Speaking with other Haskell users, most people seem to believe that
=
usually means extensional equality or substitution but is fundamentally context-dependent. Nobody provided any authoritative source for this claim. - The Haskell wiki article on monad laws states that
=
is extensional, but, again, fails to provide a source, and I wasn't able to track down any way to contact the author of the relevant edit.
The question, then: Is there any authoritative source on or standard for the semantics for =
in typeclass laws? If so, what is it? Additionally, are there examples where the intended meaning of =
is particularly exotic?
(As a side note, treating =
extensionally can get tricky. For instance, there is a Monoid (IO a)
instance, but it's not really clear what extensional equality of IO
values looks like.)
ANSWER
Answered 2022-Feb-24 at 22:30Typeclass laws are not part of the Haskell language, so they are not subject to the same kind of language-theoretic semantic analysis as the language itself.
Instead, these laws are typically presented as an informal mathematical notation. Most presentations do not need a more detailed mathematical exposition, so they do not provide one.
QUESTION
I`m using python poetry(https://python-poetry.org/) for dependency management in my project.
Though when I`m running poetry install
, its giving me below error.
ANSWER
Answered 2022-Jan-03 at 13:24I solved it by doing the following steps:-
I updated the pyproject.toml(This file contains all the library/dependency/dev dependency)with the numpy version that I installed using
pip install numpy
command.Run
poetry lock
to update poetry.lock file(contains details information about the library)Run
poetry install
again, & it should work fine.
If you are having any problems, you can comment. I`ll try to answer it.
QUESTION
I am sorry but I am really confused and leery now, so I am resorting to SO to get some clarity.
I am running Android Studio Bumblebee and saw a notification about a major new release wit the following text:
...ANSWER
Answered 2022-Feb-10 at 11:10This issue was fixed by Google (10 February 2022).
You can now update Android Studio normally.
QUESTION
I know Python //
rounds towards negative infinity and in C++ /
is truncating, rounding towards 0.
And here's what I know so far:
...ANSWER
Answered 2022-Jan-18 at 21:46Although I can't provide a formal definition of why/how the rounding modes were chosen as they were, the citation about compatibility with the %
operator, which you have included, does make sense when you consider that %
is not quite the same thing in C++ and Python.
In C++, it is the remainder operator, whereas, in Python, it is the modulus operator – and, when the two operands have different signs, these aren't necessarily the same thing. There are some fine explanations of the difference between these operators in the answers to: What's the difference between “mod” and “remainder”?
Now, considering this difference, the rounding (truncation) modes for integer division have to be as they are in the two languages, to ensure that the relationship you quoted, (m/n)*n + m%n == m
, remains valid.
Here are two short programs that demonstrate this in action (please forgive my somewhat naïve Python code – I'm a beginner in that language):
C++:
QUESTION
I'm using C# 10 new feature File-scoped namespace declaration
.
I have old code like this
...ANSWER
Answered 2021-Oct-18 at 15:27To control the code style in editorconfig use this line :
To enforce this style
QUESTION
ANSWER
Answered 2022-Jan-25 at 14:49ANSWER: Underlying problem determined to exist in IDE's compilation/build/execution routine.
Reinstall and update IDE, adoption of non-EOL JDK.
Also, I did not import existing IDE settings.
QUESTION
I asked a question yesterday about template method overloading and resolving issues using type traits. I received some excellent answers, and they led me to a solution. And that solution led me to more reading.
I landed on a page at Fluent CPP -- https://www.fluentcpp.com/2018/05/18/make-sfinae-pretty-2-hidden-beauty-sfinae/ that was interesting, and then I listened to the Stephen Dewhurst talk that Mr. Boccara references. It was all fascinating.
I'm now trying to understand a little more. In the answers yesterday, I was given this solution:
...ANSWER
Answered 2021-Dec-14 at 16:34Vocabulary
QUESTION
On the pandas tag, I often see users asking questions about melting dataframes in pandas. I am gonna attempt a cannonical Q&A (self-answer) with this topic.
I am gonna clarify:
What is melt?
How do I use melt?
When do I use melt?
I see some hotter questions about melt, like:
pandas convert some columns into rows : This one actually could be good, but some more explanation would be better.
Pandas Melt Function : Nice question answer is good, but it's a bit too vague, not much expanation.
Melting a pandas dataframe : Also a nice answer! But it's only for that particular situation, which is pretty simple, only
pd.melt(df)
Pandas dataframe use columns as rows (melt) : Very neat! But the problem is that it's only for the specific question the OP asked, which is also required to use
pivot_table
as well.
So I am gonna attempt a canonical Q&A for this topic.
Dataset:I will have all my answers on this dataset of random grades for random people with random ages (easier to explain for the answers :D):
...ANSWER
Answered 2021-Nov-04 at 09:34df.melt(...)
for my examples, but your version would be too low for df.melt
, you would need to use pd.melt(df, ...)
instead.
Documentation references:
Most of the solutions here would be used with melt
, so to know the method melt
, see the documentaion explanation
Unpivot a DataFrame from wide to long format, optionally leaving identifiers set.
This function is useful to massage a DataFrame into a format where one or more columns are identifier variables (id_vars), while all other columns, considered measured variables (value_vars), are “unpivoted” to the row axis, leaving just two non-identifier columns, ‘variable’ and ‘value’.
And the parameters are:
Logic to melting:Parameters
id_vars : tuple, list, or ndarray, optional
Column(s) to use as identifier variables.
value_vars : tuple, list, or ndarray, optional
Column(s) to unpivot. If not specified, uses all columns that are not set as id_vars.
var_name : scalar
Name to use for the ‘variable’ column. If None it uses frame.columns.name or ‘variable’.
value_name : scalar, default ‘value’
Name to use for the ‘value’ column.
col_level : int or str, optional
If columns are a MultiIndex then use this level to melt.
ignore_index : bool, default True
If True, original index is ignored. If False, the original index is retained. Index labels will be repeated as necessary.
New in version 1.1.0.
Melting merges multiple columns and converts the dataframe from wide to long, for the solution to Problem 1 (see below), the steps are:
First we got the original dataframe.
Then the melt firstly merges the
Math
andEnglish
columns and makes the dataframe replicated (longer).Then finally adds the column
Subject
which is the subject of theGrades
columns value respectively.
This is the simple logic to what the melt
function does.
I will solve my own questions.
Problem 1:Problem 1 could be solve using pd.DataFrame.melt
with the following code:
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