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Explain the use of a bit vector for determining if all characters are unique
...cause operations with bits are very low level and can be executed as-is by CPU. BitVector allows writing a little bit less cryptic code instead plus it can store more flags.
For future reference: bit vector is also known as bitSet or bitArray. Here are some links to this data structure for differen...
What is exactly the base pointer and stack pointer? To what do they point?
...egisters stay where they are, only their value is sent to the RAM from the CPU. In the amd64 mode, this gets a bit more complex, but leave that to another question.
– wigy
Jan 20 '17 at 10:42
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Building and running app via Gradle and Android Studio is slower than via Eclipse
...ject with gradle files and indexing tasks). Measure build time and process CPU with and without antivirus enabled to see if it is related.
Profiling a build
Gradle has built-in support for profiling projects. Different projects are using a different combination of plugins and custom scripts. Usin...
What is the volatile keyword useful for?
...So if Thread A is creating Singleton instance and just after creation, the CPU corrupts etc, all other threads will not be able to see the value of _instance as not null and they will believe it is still assigned null.
Why does this happen? Because reader threads are not doing any locking and unt...
PostgreSQL: Difference between text and varchar (character varying)
... increased storage space when using the blank-padded type, and a few extra CPU cycles to check the length when storing into a length-constrained column. While character(n) has performance advantages in some other database systems, there is no such advantage in PostgreSQL; in fact character(n) is usu...
Why does changing 0.1f to 0 slow down performance by 10x?
... sets FTZ (flush to zero) and DAZ (denormal are zero) in the MXCSR, so the CPU never has to take a slow microcode assist for denormals.
– Peter Cordes
Jan 16 '19 at 10:23
add ...
Evaluating a mathematical expression in a string
...rbitrary commands
eval("9**9**9**9**9**9**9**9", {'__builtins__': None}) # CPU, memory
Note: even if you use set __builtins__ to None it still might be possible to break out using introspection:
eval('(1).__class__.__bases__[0].__subclasses__()', {'__builtins__': None})
Evaluate arithmetic expr...
How to append rows to an R data frame
...t(r)
For 1E5 rows (measurements done on Intel(R) Core(TM) i7-4710HQ CPU @ 2.50GHz):
nr function time
4 data.frame 228.251
3 sqlite 133.716
2 data.table 3.059
1 rbindlist 169.998
0 placebo 0.202
It looks like the SQLite-based sulution, although r...
What data type to use for hashed password field and what length?
...le numerical value, others have more parameters there (for example to tune CPU usage and RAM usage separately).
The salt. Since the salt must be globally unique, it has to be stored for each account. The salt should be generated randomly on each password change.
The hash proper, i.e. the output of t...
How can bcrypt have built-in salts?
...ext.
What is more important : There is no hashing in this process, rather CPU expensive encryption - decryption. thus rainbow tables are less relevant here.
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