# Questions tagged [data-compression]

The tag has no usage guidance.

203 questions
Filter by
Sorted by
Tagged with
106 views

### Can a 600 MB text file with digits of the square root of 2 be compressed to 600 KB?

I have a simple script to calculate gaps in a sequence of digits of the square root of 2 (or any other multi-precision constant). As input, I generated files with the bigfloat module in Python: ...
25 views

I'm confused about the point of adaptive arithmetic coding. I understand that static arithmetic coding involves using preset probabilities of symbols that remain static during the whole process. I ...
19 views

### Significance of model in arithmetic coding

I am trying to understand the concept of arithmetic coding, i understand how the range is subdivided after each character is read from the string. But i am unable to understand why using a more ...
21 views

### How does value decompression work for Facebook's Gorilla in the case where count of leading zeroes is not stored

I am referring to this paper: http://www.vldb.org/pvldb/vol8/p1816-teller.pdf My question is regarding section 4.1.2 where it says: When XOR is non-zero, calculate the number of leading and ...
24 views

### Source code or detailed explanation of “WKS” virtual memory compression algorithm?

I've been trying to find information on various program data virtual memory compression algorithms that are in the "WK" family of algorithms. So far, I've been successful with the "WKdm" compression ...
30 views

### How do you work out the Huffman code for an extension?

I have worked out the following: v = 1101 0010 1101 0101 0100 1000 P(0) = 0.54 P(1) = 0.46 A = {0,1} I have also worked out question (c) to be: H(A^2) = 1.991 and H(A^3) = 2.9859 I am having ...
39 views

### Is the source file size smaller than the executable file size?

Wondering if compilation increases file size in general, is the source file size smaller than the executable file size?
30 views

### How would I make sure my compressed string has the smallest length possible?

I'm trying to make a function that takes a string and compresses the repeating blocks. The code I'm using is implemented in such a way that a single character like 'a' would be converted to '1(a)' ...
34 views

### Data compression - Entropy

Let's say I have an alphabet $$\Sigma = \{A, B, C, D, E\}$$ with probabilities $$P(A) = P(B) = P(C) = 0.25 \text{ and } P(D)=P(E) = 0.125.$$ I know that the entropy then is: H(\Sigma) = 3 \cdot 0....
26 views

### on-the-fly decompress a flat-file database

I'm facing the following problem. I have a flat-file database (e.g. CSV). Since it's relatively large to store in memory, I'd like to compress it. Given a key, I need to return the uncompressed text (...
36 views

### Alternatives to multiplication/division/modulo for encoding choices?

The obvious way to encode, with minimum entropy, choosing s out of n (equiprobable) choices when x is already encoded is to identify s with a number [0, n) and set x = n * x + s, decoded with s = x % ...
85 views

### Applying SVD compression to integral point images

Suppose that we have an $m\times n$ matrix $A$ of rank $n$, whose entries are 8-bit unsigned integers obtained from a grayscale image. Now we want to apply SVD to $A$ and to use the first $k$ singular ...
24 views

### Space-efficient data structure for analytical querying of multiple branching evolutions of a dataset

Problem Description I have a data state space: a set of data sets, each of which can be modelled as a collection of arbitrary key-value pairs. These data sets are each a branch of evolution of a ...
62 views

### Data Compression :Compress a Compressed File

Suppose we have file A that has been compressed by the the method B and the output-file is C, now if I am not wrong We can not compress C more by method B, but there might another method=algorithm D ...
47 views

### How a Data Compression Software Reads a File as pure Binary File and makes Output?

I have an hybrid compression technique I want to implement, my implementation is (so far): I can encode a string into a encoded compressed string. These are binary strings. For example, I read texts ...
24 views

66 views

### Algorithm for estimating lossless compression factor

Is there any algorithm for estimating how well certain array of bytes could be compressed in lossless manner? Usage for me is to automatically choose "best" data reorder method without knowing what ...