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+5
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// And then I replaced the idiomatic Rust code for working with block like
for (dline, (sline0, sline1)) in dst.chunks_mut(dstride).zip(tmp.chunks(TMP_BUF_STRIDE).zip(tmp2.chunks(TMP_BUF_STRIDE))).take(h) {
for (pix, (&a, &b)) in dline.iter_mut().zip(sline0.iter().zip(sline1.iter())).take(w) {
*pix = ((u16::from(a) + u16::from(b) + 1) >> 1) as u8;
}
}
// with raw pointers:
unsafe {
let mut src1 = tmp.as_ptr();
let mut src2 = tmp2.as_ptr();
let mut dst = dst.as_mut_ptr();
for _ in 0..h {
for x in 0..w {
let a = *src1.add(x);
let b = *src2.add(x);
*dst.add(x) = ((u16::from(a) + u16::from(b) + 1) >> 1) as u8;
}
dst = dst.add(dstride);
src1 = src1.add(TMP_BUF_STRIDE);
src2 = src2.add(TMP_BUF_STRIDE);
}
}
What do you know, the total decoding time for the test clip I used shrank from 6.6 seconds to 4.9 seconds. That’s just three quarters of the original time!
And here is the problem. In theory if Rust compiler knew that the input satisfies certain parameters i.e. that there’s always enough data
to perform full block operation in this case, it would be able to optimise code as good as the one I wrote using pointers or even better.
But unfortunately there is no way to tell the compiler that input slices are large enough to perform the operation required amount of times.
Even if I added mathematically correct check in the beginning it would not eliminate most of the checks.
https://codecs.multimedia.cx/2021/05/missing-optimisation-opportunity-in-rust/
3.14159265,
17 Августа 2021
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+7
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console.log(parseInt(0.5)); // 0
console.log(parseInt(0.05)); // 0
console.log(parseInt(0.005)); // 0
console.log(parseInt(0.0005)); // 0
console.log(parseInt(0.00005)); // 0
console.log(parseInt(0.000005)); // 0
console.log(parseInt(0.0000005)); // 5
https://ideone.com/YMWUGq
Возможно баян, спижжено с https://vk.com/wall-72495085_1267978
3_dar,
17 Августа 2021
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0
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package test.sandbox
object Main {
def foo(implicit a: Int): Int = a * 2
def main(args: Array[String]): Unit = {
{
import Test._
val result = foo
println(s"Result1 = $result") // Result1 = 42
}
{
implicit val x = 16
println(s"Result2 = $foo") // Result2 = 32
}
}
}
object Test {
implicit val x: Int = 21
}
"Scala" — сахарная. (*^‿^*)
PolinaAksenova,
16 Августа 2021
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type int = 1;
function makeRangeIterator(start = 0, end = 10000, step = 1) {
print("makeRangeIterator.");
let nextIndex = start;
let iterationCount = 0;
const rangeIterator = {
next() {
let result: [value: int, done: boolean];
if (nextIndex < end) {
result = [nextIndex, false];
nextIndex += step;
iterationCount++;
return result;
} else {
result = [iterationCount, true];
}
return result;
},
};
return rangeIterator;
}
function main() {
let it = makeRangeIterator(1, 10, 2);
let result = it.next();
while (!result.done) {
print(result.value); // 1 3 5 7 9
result = it.next();
}
print("done.");
}
Ну вот и все... позвольте мне представить самый сложный кусок когда либо компилированный моей программой. но ввиду того что "трамплины" хрен знает как работают то придется этот код "забанить" до лучших времен. Но он рабочий
ASD_77,
16 Августа 2021
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0
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Автомобиль-русофоб
https://habr.com/ru/post/572984/
Я нашел статью про Насру (formerly Gologub).
JloJle4Ka,
15 Августа 2021
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C 5.2s gcc test.c
C++ 1m 25s g++ test.cpp
Zig 10.1s zig build-exe test.zig
Nim 45s nim c test.nim
Rust Stopped after 30 minutes rustc test.rs
Swift Stopped after 30 minutes swiftc test.swift
D Segfault after 6 minutes dmd test.d
Rust and Swift took too long to compile 400k lines, so I tried smaller numbers:
# lines Rust Swift D
2k 3.4s 0.8s
4k 9.0s 1.0s
8k 30.8s 2.3s
20k 3m 52s 11.8s 4.7s
100k - 5m 57s segfault
https://vlang.io/compilation_speed
3.14159265,
15 Августа 2021
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class S
{
print()
{
print("Hello World");
}
}
interface IPrn
{
print();
}
function run(iface:IPrn)
{
iface.print();
}
function main() {
const s = new S();
let iface = <IPrn>s;
iface.print();
run(s);
}
короче новый говнокод подоспел. Т.к. вы все тут самые умные я не раскажу в чем фича. Сами догадаетесь
ASD_77,
15 Августа 2021
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+2
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// https://github.com/seanbaxter/circle/blob/master/examples/README.md#tldr
// ...
// Circle's primary syntactic element is the @meta keyword, which runs the prefixed statement
// during source translation (or during template instantiation in dependent contexts).
// https://github.com/seanbaxter/circle/blob/master/examples/README.md#same-language-reflection
// duff1.cxx
void duff_copy1(char* dest, const char* source, size_t count) {
const char* end = source + count;
while(size_t count = end - source) {
switch(count % 8) {
case 0: *dest++ = *source++; // Fall-through to case 7
case 7: *dest++ = *source++; // Fall-through to case 6...
case 6: *dest++ = *source++;
case 5: *dest++ = *source++;
case 4: *dest++ = *source++;
case 3: *dest++ = *source++;
case 2: *dest++ = *source++;
case 1: *dest++ = *source++;
break;
}
}
}
// Reproduced above is a simplified version of Duff's device, an infamous memcpy function designed
// to reduce the amount of branching in the operation. (The loop is optimally interleaved with the switch,
// but I'm trying to illustrate some other points and don't want to add to the confusion.) Once we enter the
// switch, perform an assignment and unconditionally progress to the next case statement. This algorithm
// cries out for automation. The case statements have indices that run from 8 down to 1, modulo 8. Can we give it the Circle treatment?
// duff2.cxx
void duff_copy2(char* dest, const char* source, size_t count) {
const char* end = source + count;
while(size_t count = end - source) {
switch(count % 8) {
@meta for(int i = 8; i > 0; --i)
case i % 8: *dest++ = *source++;
break;
}
}
Но гомоиконности таким подкостыливанием вы естественно не добавите!
j123123,
14 Августа 2021
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type int = 1;
function main() {
let result: [value: int, done: boolean];
let v: int | undefined;
v = 1;
result = [v, false];
print(result[0], result[1]);
assert(result[0] == 1);
assert(result[1] == false);
}
опа. новый говнокодец подоспел. а кто знает какая проблема решалась в данном коде?
ASD_77,
14 Августа 2021
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+1
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QSqlQuery& SQLConnect::get()
{
if ( makeConnection() ) {
query = QSqlQuery(mDb);
return query;
}
QSqlQuery empty;
return empty;
}
bool SQLConnect::makeConnection()
{
mDb = SQLConnectPool::Instance().get();
return true;
}
Раньше компилилось и не замечал, а тут на новом компиляторе начал кидать ошибки и решил посмотреть, что же там напроектировали
avk17,
14 Августа 2021
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