TurboPFor: Integer Compression

[dnd]

+ TurboPFor - Integer Compression
- 100% C (C++ compatible headers), w/o inline assembly
- Direct Access
- Integrated (SIMD) delta/Zigzag
- Full range 16/32/64
- Access TurboPFor incl. SIMD from Java as fast as calling from C.

+ Features
- "Variable Byte"

- "Variable Simple"

- Scalar "Bit Packing" with Direct/Random Access (zero decompression)
- "SIMD Bit Packing"

- "Elias Fano"

- Novel "TurboPFor" scheme with direct access.
Outstanding compression and speed.

- New: Scalar & SIMD Transform: Delta, Zigzag, Transpose/Shuffle, ...

+ Inverted Index ...do less, go fast!

TurboPFor: Fastest Integer Compression

[dnd]

TurbPFor: Integer Compression Updated: now support for gcc, clang & mingw-w64.

[dnd]

New Update:
+ more functions
+ 64 bits integer lists
+ Java Critical Native Interface. Access TurboPFor incl. SIMD from Java as fast as calling from C to C
+ Benchmark comparing to delta+transpose+lz4 (similar to delta+blosc).


see: TurboPFor Integer Compression

[dnd]

TurboPFor Integer Compression new Update:
+ Zigzag encoding/decoding
+ Improved speed

+ My github answer to "Comparison with Blosc can be improved" showing applications of "Integer Compression"

TurboPFor compress better, ~12 times faster and decompress ~13 times faster than blosc w/ zlib

[mitra]

Hello,

When I am searching for fastest bit packing/unpacking techniques for the sake of my application, I came across TurboPFor. After I gone through the source code, I am left with following doubts.

Why is the TurboPFor faster than any other packing/unpacking techniques? I tried exploiting the source code which I took from github but found nothing very special to make it that faster. W/o even using SIMD, it is produced unbelievable results. Please explain the algorithm u followed to pack and unpack the numbers with that huge speeds.

I also found that, the value of number of bits into which the intergers should be packed is calculated based on input array. Is that where you are achieving performance by selecting optimal 'b' size ?

Why are you declaring output array as unsigned char* when it is anyway typecasted to uint64_t* while packing ?

And, Why are you packing into uint32_t* array instead of uint64_t* when the 'b' size is 32 ?

Thank you.

[dnd]

..Why is the TurboPFor faster than any other packing/unpacking techniques?

Glad you have interest on TurboPFor Integer Compression.
Well, TurboPFor is exploiting capabilities avaiable on modern super scalar processors like branchless and out of order execution.
Additionally, the dependencies between successive instructions are reduced to a minimum. The memory access/transfer is also reduced by the compression.

Why are you declaring output array as unsigned char* when it is anyway typecasted to uint64_t* while packing ?

All the TurboPFor functions have similar API interface and "char *" is used for the compressed buffer. This permits a consistent API interface.
The output buffer is also not a multiple of "uint64_t". Memory output is done using 64 bits chunks.

And, Why are you packing into uint32_t* array instead of uint64_t* when the 'b' size is 32 ?

The bitpacking macros are template generated, so there is no difference in coding between differents b sizes.

I suggest you read the papers included in the references.

[mitra]

I have an integer array and should pack the values into a 'long' array where each long element has two integers (two 32 bit integers packed into one 64 bit long value, reducing size to 50%). Simillarly unpack that when needed. Could you please suggest the fastest way to this packing/unpacking ?
Here is what I have done
packing :

while(k < pack_count)
{
pack[k] = ((long int)data[z]<<32|(long int)data[z+1]<<0);
k++;
z=z+2;
}

where pack_count = (no. of integers)/2

unpacking :

while(i<count)
{
temp[++j] = ((pac[x] & 0xffffffff00000000) >> 32);
temp[++j] = ((pac[x] & 0x00000000ffffffff) >> 0);
i++; x++;
}

By this I couldn't achieve that high speed as we get from turbopfor.

[dnd]

Simply use a single call to bitpack/vp4dc w/ the integer Array. You have not to pack first to a 64 bits long.

[mitra]

Thank you!

Can we achieve "fixed length encoding" with this high speed??
If yes, can you suggest how to do that?

[dnd]

Look at icbench.c please.

[mitra]

Hello,

I am dealing with long values and gave the following instruction : ./icbench -eturbopack -n100 -M12345678223
I have a column with 11-digit values (long) and I am trying to pack them using turbopack.
But I got the error as : icbench.c:zipfgen:563:mallo error

The 563rd line in code is : if(!(zmap = malloc(m*sizeof(zmap[0])))) die("mallo error\n");

How to rectify this?
I dont want to send data from file as in real time I dont get data from a file, I get data from memory.
I have checked for any options which specify the turbopack to be 64-bit, but I dint found any such option in what you provided.

Kindly help me out in packing and unpacking 'long' values using turbopack.

[mitra]

Hello,

How should the 'b' value, i.e the number of bits into which packing should be done, is calculated for long values(64-bit)?
There is a function 'BITSIZE32' for 32-bit. Simillarly is there any way to calculate for 64-bit?

Thank you.

[dnd]

You can simply use BITSIZE as in the macro BITSIZE32 (see bitutil.h):
#define BITSIZE64(in, n, b) BITSIZE(in, n, b, 64)

[mitra]

(out of curiosity)

Can you make it a Apache/BSD licensed package? Or atleast the files like bitpack64_.h and bitunpack64_.h can be of more generic license so that people can write their own (commercial)applications and use the packing/unpacking power of turbopfor.

[dnd]

Sorry, but actually there are not plans to change the license.

[joerg]

congratulation - sounds good
---
lzturbo 1.2 Copyright (c) 2007-2014 Hamid Buzidi Aug 11 2014

Usage: lzturbo <options> <filename1> .. <filenameN> DESTINATION_DIR
<options>
-ml m: compression method (1..4), l:compression level (0,1,2,9).
-p# #: number of processors/cores (default=autodetect). 0=disable multithre
ading
-b# #: block size in mb (default 64)
-r compress/decomp directories recursively
-d decomp
-f force overwrite of output file
-o write on standard output
Ex.: lzturbo -32 -f file.jpg ab*.txt backup_dir
lzturbo -49 -r mydir\* backup_dir
lzturbo -10 file file.lzt
cat file | ./lzturbo -of -10 >file.lzt
lzturbo -d -r backup_dir\* restore_dir
lzturbo -d file.lzt file
---
# Usage:
## Compression
lzturbo -ml [-rfo] [-p#] <filename1> .. <filenameN> DESTINATION_DIR

ml
m: compression method (1..4), 1fastest decompression) ... 4: (best compression)
l: compression level (0..2,9), 0fastest compression) ... 9: (best but slow compression)
decompression time same for all levels.
ml=10, 11, 12, 19 : Fast byte output
20, 21, 22, 29 : Efficient byte ouptut
30, 31, 32, 39 : Asymmetric Numeral System TurboANX w. JIT switching [scalar/SSE/AVX2]
? ? ? 49 : Bitwise Arithmetic Coding (?=40,41,42 not available)

b#
#: block size in mb (max. 1024), default: 64/128, 128mb for level 9
use b1024 for max. compression and large files.

## Decompression
lzturbo -d -p# [-fo] <filename1> .. <filenameN> DESTINATION_DIR

## Options for compression/decompression:
r compress/decompress directories recursively
p# #: number of processors/cores (default=autodetect). 0=disable multithreading
f force overwrite of output file
o write on standard output
S disable ANS SIMD (method 3)
DESTINATION_DIR: Destination directory or destination file.

## Decompression examples:
lzturbo -d enwik9.lzt restore_dir
lzturbo -d *.lzt restore_dir
lzturbo -d -r backup_dir\* restore_dir
lzturbo -d file.lzt file

replace '\' by '/' for linux.
---
best regards

[joey]

Hello,

In TurboPfor's github page there is a table given with all comparisons among different algorithms.
I found there is not much difference between turbopack-scalar version and turbopackV, the SIMD version of it.

Theoritically there should be 4X improvement when SIMD is used as we treat 4 integers at a time.
But There is very minimal improvement despite running on 100Million data (If it is that there should be huge data to compensate overhead of parallel execution, 100Million is huge enough I guess).

Could you please tell why there is very minimal difference in speed between scalar and SIMD version of turbopack?

[dnd]

...I found there is not much difference between turbopack-scalar version and turbopackV, the SIMD version of it.
Theoritically there should be 4X improvement when SIMD is used as we treat 4 integers at a time...

Well, there are some reasons:

- The scalar version TurboPack is higly optimized by using 64 bits registers and exploiting out of order execution.
Other slower scalar bitpacking (ex. in FastPFor) are using 32-bits registers or direct memory to memory bit packing.

- In my benchmarks, I'm always using practical large arrays to avoid the cache scenario found in micro-benchmarks from other authors.
In the practice you are rarely repeatedly accessing the data that is already in the cache.
Memory access becomes more and more important especially on multithreaded applications.
For ex. search engines or databases are randomly accessing several gigabytes to answer queries.
You can see the effect by using a small array (Ex. ./icbench -m0 -M255 -n1m)

- but, in general the SIMD version TurboPackV is slightly faster and I'm using it in the inverted index app.


SIMD is also not always faster and is depending on the implementation of scalar function used in the benchmark, see for ex. the TurboVByte vs MaskedVByte.
The scalar "transpose" (shuffle) function in TurboPFor is also faster than the SIMD "shuffle" version in blosc.

[mitra]

The explaination was very useful.

[joey]

Basically there are many algorithms for integers but very few of them will scale for long. I am happy that Turbopfor is one among them.

""What if SIMD is applied to Long data type too? Will it accelerate the process of pack/unpack?""

Long is present in almost every table of a typical database. Can you suggest ways to accelerate compress/decompress of long datatype?

[dnd]

""What if SIMD is applied to Long data type too? Will it accelerate the process of pack/unpack?""

It is possible to accelerate TurboPack64 by using SIMD for bit sizes <=32, but it is difficult to predict the performance before implementing.

Long is present in almost every table of a typical database. Can you suggest ways to accelerate compress/decompress of long datatype?

"Integer Compression" is highly depending on the distribution of your data.
You can try "variable simple" with a large block size. If most integers are small, you can try TurboPFor or TurboPack otherwsise try TurboVbyte.
If the cardinality of the data is small, try to use dictionary mapping for better compression.

[dnd]

Actually, you can use direct access only with the scalar version.
Direct Access means, you can extract or update a single value (by position) without decompressing the whole block.
This is usefull for example in column oriented databases (column stores).
The Index search deliver a row number, that you can use to access directly the remaining row columns.

[dnd]

New Skylake benchmarks: Integer Compression with more than 3 billions! per seconds or more than 12 GB/s.

[dnd]

TurboPFor (PFor/PFordelta) decoding in the "TurboPFor: Integer Compression" improved by 30%!

[dnd]

Scalar Variable byte "TurboVByte" in "TurboPFor Integer Compression" improved and now up to 25%! faster.
More efficient and faster than ANY other variable byte implementation. Even faster than "SIMD MaskedVByte".

[dnd]

TurboPFor Integer Compression update:
QMX described in "Compression, SIMD, and Postings Lists" added to the benchmark app.

[dnd]

State of the art TurboPFor Integer Compression compared and presented at ADCS2016
Conference: "In Vacuo and In Situ Evaluation of SIMD Codecs"

[dnd]

New TurboPFor Integer Compression update incl. AVX2:

- New TurboPack AVX2 bitpacking: decoding 10 Billions integer/s!!!! (40 GB/s).
- New TurboPFor AVX2, now 50%!!!! more faster
- New TurboPFor Hybrid adaptive, better compression and more faster
- New TurboVByte scheme: more compression and speed

[dnd]

- New Improved encoding for sorted/unsorted lists
- TurboPFor ZigZag encoding for unsorted integer lists
- TurboFOR encoding for sorted + unsorted integer lists
- improved documentation
- improved JAVA interface
- New high level functions as simple as memcpy

[dnd]

New: (Differential) Finite Context Method FCM/DFCM for fast Floating Point Compression

See: TurboPFor Integer Compression