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Replacing a 32-bit loop counter with 64-bit introduces crazy performance deviations with _mm_popcnt_
...), %r11
movq 24(%rbx,%rdx,8), %rbp
addq $4, %rdx
# This time reuse "rax" for all the popcnts.
popcnt %r9, %rax
add %rax, %rcx
popcnt %r10, %rax
add %rax, %rsi
popcnt %r11, %rax
add %rax, %r8
popcnt %rbp, %rax
add %rax, %rdi
cmpq ...
Is multiplication and division using shift operators in C actually faster?
...ence of shifts & adds in microcode.
Bottom line--don't spend a lot of time worrying about this. If you mean to shift, shift. If you mean to multiply, multiply. Do what is semantically clearest--your coworkers will thank you later. Or, more likely, curse you later if you do otherwise.
...
How can I check if a file exists in Perl?
....
-B
File is a “binary” file (opposite of -T).
-M
Script start time minus file modification time, in days.
-A
Same for access time.
-C
Same for inode change time (Unix, may differ for other platforms)
...
When should the xlsm or xlsb formats be used?
...
.xlsx loads 4 times longer than .xlsb and saves 2 times longer and has 1.5 times a bigger file. I tested this on a generated worksheet with 10'000 rows * 1'000 columns = 10'000'000 (10^7) cells of simple chained =…+1 formulas:
╭─...
Why does modern Perl avoid UTF-8 by default?
...
Declare that this source unit is encoded as UTF‑8. Although once upon a time this pragma did other things, it now serves this one singular purpose alone and no other:
use utf8;
Declare that anything that opens a filehandle within this lexical scope but not elsewhere is to assume that that strea...
How do I get an object's unqualified (short) class name?
... => array(),
);
for($r = 0; $r < $rounds; $r++){
$start = microtime(true);
for($i = 0; $i < $num; $i++){
$a->getClassReflection();
}
$end = microtime(true);
$res["Reflection"][] = ($end-$start);
$start = microtime(true);
for($i = 0; $i < $num; $i...
How can you profile a Python script?
Project Euler and other coding contests often have a maximum time to run or people boast of how fast their particular solution runs. With Python, sometimes the approaches are somewhat kludgey - i.e., adding timing code to __main__ .
...
What's the main difference between int.Parse() and Convert.ToInt32
...hod has an overload for loads of types, there among them System.String, no time will be lost discerning the type. The actual code does nothing but return 0 for null values, and int.Parse(value, CultureInfo.CurrentCulture) for everything else.
– Andreas Eriksson
...
What's the point of JAXB 2's ObjectFactory classes?
...ated constraints on the values that an element's contents can take on, sometimes you need to create actual JAXBElement objects. They are not usually trivial to create by hand, so the create* methods do the hard work for you. Example (from the XHTML 1.1 schema):
@XmlElementDecl(namespace = "http://w...
What is the concept of erasure in generics in Java?
...really mean (i.e. what the type argument for T is) and verifies at compile time that you're doing the right thing, but the emitted code again just talks in terms of java.lang.Object - the compiler generates extra casts where necessary. At execution time, a List<String> and a List<Date> ...