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John Carmack's Unusual Fast Inverse Square Root (Quake III)
...ng result, until required accuracy is met. This is exactly how it works in CPU/FPU! But it seems that only one iteration was enough, which was also a blessing for the speed. CPU/FPU does as many iterations as needed to reach the accuracy for the floating point number in which the result is stored an...
What's the difference between a word and byte?
... or even 12 bit machines.
The byte is the smallest addressable unit for a CPU. If you want to set/clear single bits, you first need to fetch the corresponding byte from memory, mess with the bits and then write the byte back to memory.
The word by contrast is biggest chunk of bits with which a pro...
Error 908: Permission RECEIVE_SMS has been denied. - App Inventor 2 中...
...到错误908（权限接收短信）的讨论。一位用户遇到了这个问题，并询问是否有人知道如何解决。其他用户提供了一些可能的解决方案，包括检查应用程序权限设置、确保手机上的权限设置正确、重新编译应用程序等。有人建议检...
What is a “cache-friendly” code?
...hit/miss usually refers to a hit/miss in the highest level of cache in the CPU -- by highest level I mean the largest == slowest. The cache hit rate is crucial for performance since every cache miss results in fetching data from RAM (or worse ...) which takes a lot of time (hundreds of cycles for RA...
C语言结构体里的成员数组和指针 - c++1y / stl - 清泛IT社区，为创新赋能！
...问0x4的内存地址，不crash才怪。于是，你一定会有如下的问题：1）为什么不是 13行if语句出错？f.a被初始化为空了嘛，用空指针访问成员变量为什么不crash？2）为什么会访问到了0x4的地址？靠，4是怎么出来的？3）代码中的第4行...
When should I use a table variable vs temporary table in sql server?
...OM master..spt_values v1, master..spt_values v2
SET STATISTICS TIME ON
/*CPU time = 7016 ms, elapsed time = 7860 ms.*/
UPDATE @T SET Flag=1;
/*CPU time = 6234 ms, elapsed time = 7236 ms.*/
DELETE FROM @T
/* CPU time = 828 ms, elapsed time = 1120 ms.*/
UPDATE #T SET Flag=1;
/*CPU time = 672 m...
Performance optimization strategies of last resort [closed]
...tion process that at the core was a 3-vector dotted with a 3x3 matrix. The CPU had a matrix multiply in hardware that left out some of the cross terms and went real fast compared to all the other ways to do it, but only supported 4x4 matrices and 4-vectors of floats. Changing the code to carry aroun...
Controlling fps with requestAnimationFrame?
...actually seems to work in keeping the framerate down and so not cooking my CPU. And it's so simple. Cheers!
– phocks
Sep 1 '17 at 7:09
...
Limitations of SQL Server Express
...
There are a number of limitations, notably:
Constrained to a single CPU (in 2012, this limitation has been changed to "The lesser of one socket or four cores", so multi-threading is possible)
1GB RAM (Same in 2008/2012)
4GB database size (raised to 10GB in SQL 2008 R2 and SQL 2012) per databa...
#pragma pack effect
...alks about some fairly extreme alignment (aligning on 4KB boundaries). The CPU expects certain minimum alignments for various data types, but those require, in the worst case, 8-byte alignment (not counting vector types which may require 16 or 32 byte alignment). Not aligning on those boundaries gen...