bit-mask | An NPM for creating and altering bitmasks | Runtime Evironment library

This is a partial code for a bit-masking problem. I have n sets of colored balls and each set has 10 types of balls. For each set the types of balls present is given by a bit-mask string, like "0000000001" means only type one ball is present. I am creating 2^n size array for each possible combination of "sets" and assigning the strings to those combinations. In the given snippet, I am assigning each individual set in the 2^n array with it's corresponding string/balls distribution.

This snippet is using 2^n sized string array and it gives seg-fault after 4 assignments. I have also tried with a 2^n sized integer array, it gives seg-fault after 10 assignments. I have also tried vector instead of array.

The code works perfectly for small n like 5, 10. However, I am getting errors for n=100.

Consider we are defining a class that:

1. Many instances of that class will be created
2. We must store under 32 flags in each instance that keeps states or some options, etc.
3. Defining flags count is fixed and we no-need to keep it in an enumerable variable in runtime. (say we can define separate bool variables, rather than one bool array)
4. Some properties (from each instance) is depended on our flags (or options) And flags states Will be used (read/write) in a hot call path in our application.

Note: Performance is important for us in that Application.

And As assumptions #1 and #4 dictated, we must care about both speed and memory-load in balance

Obviously we can implement our class in several ways. For example defining a flags Enum field, Or using a BitVector, Or defining separate (bool or Enum or int ...) variables, Or else defining uint variable and using bit-masks, to keep the state in each instance. But:

• Which is The Most Efficient way to keep status flags for this situation?

• Is it ( = the most efficient way) deeply depends on current in-using tools such as Compiler or even Runtime (CLR)?

I want to store 2D arrays of different length as an AwkwardArray, store them as Parquet, and later access them again. The problem is that, after loading from Parquet, the format is BitMaskedArray and the access performance is a bit slow. Demonstrated by the following code:

Writing a ZMM register can leave a Skylake-X (or similar) CPU in a state of reduced max-turbo indefinitely. (SIMD instructions lowering CPU frequency and Dynamically determining where a rogue AVX-512 instruction is executing) Presumably Ice Lake is similar.

(Workaround: not a problem for zmm16..31, according to @BeeOnRope's comments which I quoted in Is it useful to use VZEROUPPER if your program+libraries contain no SSE instructions? So this strlen could just use vpxord xmm16,xmm16,xmm16 and vpcmpeqb with zmm16.)

@BeeOnRope posted test code in an RWT thread: replace vbroadcastsd zmm15, [zero_dp] with vpcmpeqb k0, zmm0, [rdi] as the "dirtying" instruction and see if the loop after that runs slow or fast.

I assume executing any 512-bit uop will trigger reduced turbo temporarily (along with shutting down port 1 for vector ALU uops while the 512-bit uop is actually in the back-end), but the question is: Will the CPU recover on its own if you never use vzeroupper after just reading a ZMM register?

(And/or will later SSE or AVX instructions have transition penalties or false dependencies?)

Specifically, does a strlen using insns like this need a vzeroupper before returning? (In practice on any real CPU, and/or as documented by Intel for future-proof best practices.) Assume that later instructions may include non-VEX SSE and/or VEX-encoded AVX1/2, not just GP integer, in case that's relevant to a dirty-upper-256 situation keeping turbo reduced.

I recently ran across this code from a stackoverflow question:

I'm coding a personal project in Java right now and have recently been using bit operations for the first time. I was trying to convert two bytes into a short, with one byte being the upper 8 bits and the other being the lower 8 bits.

I ran into an error when running the first line of code below.

In order to speed up my Java Code for a problem, I have been working specifically on a Class that does bit-wise operations with 128Bits by manipulating two longs (See implementation). I also actually only need this datastructure for 100 Bits, but i figured there was no better way to implement this.

I am doing an ARKit app for my IT assignment and I followed a guide to bit-masking and collision and I got it to work however it only works with a simple box and not my 3D model so is there a way to convert this code to the one at the bottom or am I doing something wrong? because the top code doesn't appear however the bottom one does:

I am currently working on some networking code (this is my first server) and had a quick question about optimizing a specific function which writes values as bits and then packs them into a byte. The reason for optimizing this function is because it is used thousands of times each server tick for packing data to be sent to several clients.

An example may serve better in order to explain what the function tries to accomplish: The value 3 can be represented by two bits. In binary, it would look like 00000011. The function would turn this binary value into 11000000. When the function is called again, it would know to start from the 3rd most significant bit (3rd from the right/decimal 32) and write at most up to 6 bits into the current byte. If then there were remaining bits to write, it would start on a new byte.

The purpose of this is to save space if you have multiple values that can be less than byte.

My current function looks like this: