mishev / mastr_lzss

ɑɚɫɬɶ3. ȺɥɝɨɪɢɬɦɵɝɪɭɩɩɵL

ȼɜɟɞɟɧɢɟ

ȼ ɷɬɨɣ ɫɬɚɬɶɟ ɪɟɱɶ ɩɨɣɞɟɬ ɨɛ ɚɥɝɨɪɢɬɦɟ, ɤɨɬɨɪɵɣ ɥɟɠɢɬ ɜ ɨɫɧɨɜɟ ɬɚɤɢɯ ɢɡɜɟɫɬɧɵɯ ɩɪɨɝ- ɪɚɦɦ-ɚɪɯɢɜɚɬɨɪɨɜ, ɤɚɤ PKZIP, LHA, ARJ, Stacker, Dblspace ɢɦɧɨɝɢɯɞɪɭɝɢɯ. ɋɜɨɢɦɩɨɹɜɥɟɧɢɟɦ ɨɧ ɨɛɹɡɚɧ ɞɜɭɦ ɢɫɫɥɟɞɨɜɚɬɟɥɹɦ ɢɡ ɂɡɪɚɢɥɹ: əɤɨɛɭɁɢɜɭ ɢ Ⱥɛɪɚɯɚɦɭ Ʌɟɦɩɟɥɭ (Jacob Ziv & Abraham Lempel). ȼ 1977 ɝɨɞɭɨɧɢ ɨɩɭɛ-

ɥɢɤɨɜɚɥɢ ɪɚɛɨɬɭ [1]. ȿɟɩɨɹɜɥɟɧɢɟ ɨɡɧɚɦɟɧɨɜɚɥɨ ɧɚɱɚɥɨ ɧɨɜɨɣ ɷɪɵ ɜ ɫɠɚɬɢɢ ɢɧɮɨɪɦɚɰɢɢ. ɉɪɚɤɬɢɱɟɫɤɢ ɜɫɟ ɫɨɜɪɟɦɟɧɧɵɟ ɤɨɦɩɶɸɬɟɪɧɵɟ ɩɪɨɝɪɚɦɦɵ-ɚɪɯɢɜɚɬɨɪɵ ɢɫɩɨɥɶɡɭɸɬ ɬɭ ɢɥɢ ɢɧɭɸ ɦɨɞɢɮɢɤɚɰɢɸ ɚɥɝɨɪɢɬɦɚ LZ. ȼ ɷɬɨɦ ɫɜɟɬɟ ɫɭɞɟɛɧɵɟ ɬɹɠɛɵ ɤɨɦɩɚɧɢɣ Microsoft ɢ Stac Electronics ɩɨɩɨɜɨɞɭɢɯ ɭɬɢɥɢɬ Dblspace ɢ Stacker ɜɵɝɥɹɞɹɬɧɟɫɤɨɥɶɤɨɡɚɛɚɜɧɨ.

Ɉɫɧɨɜɧɚɹɢɞɟɹɚɥɝɨɪɢɬɦɚ

Ɉɞɧɨɣ ɢɡ ɩɪɢɱɢɧ ɲɢɪɨɤɨɝɨ ɪɚɫɩɪɨɫɬɪɚɧɟɧɢɹ ɚɥɝɨɪɢɬɦɚLZɫɬɚɥɚɟɝɨɢɫɤɥɸɱɢɬɟɥɶɧɚɹɩɪɨɫɬɨɬɚ. ȼɫɩɨɦɧɢɦ ɩɟɪɜɨɟ ɱɟɬɜɟɪɨɫɬɢɲɶɟ ɛɟɫɫɦɟɪɬɧɨɝɨ«ȿɜɝɟɧɢɹɈɧɟɝɢɧɚ»:

Ɇɨɣɞɹɞɹ,ɫɚɦɵɯɱɟɫɬɧɵɯɩɪɚɜɢɥ, Ʉɨɝɞɚɧɟɜɲɭɬɤɭɡɚɧɟɦɨɝ, Ɉɧɭɜɚɠɚɬɶɫɟɛɹɡɚɫɬɚɜɢɥ ɂɥɭɱɲɟɜɵɞɭɦɚɬɶɧɟɦɨɝ.

ȿɝɨɩɪɢɦɟɪ...

Ɉɛɪɚɬɢɬɟ ɜɧɢɦɚɧɢɟ ɧɚ ɬɨ, ɱɬɨ ɉɭɲɤɢɧ ɢɡɛɟɝɚɟɬ ɩɨɜɬɨɪɧɨɝɨ ɢɫɩɨɥɶɡɨɜɚɧɢɹ ɩɨɞɫɬɪɨɤɢ «Ɇɨɣ ɞɹɞɹ». ɋɧɚɱɚɥɚ ɜɦɟɫɬɨ ɧɟɟ ɢɫɩɨɥɶɡɭɟɬɫɹ ɦɟɫɬɨɢɦɟɧɢɟ «ɨɧ», ɡɚɬɟɦ — «ɟɝɨ». ɉɪɢ ɷɬɨɦ ɢɧɮɨɪɦɚɬɢɜɧɨɫɬɶ ɜɫɟɝɨ ɫɨɨɛɳɟɧɢɹ ɧɢɫɤɨɥɶɤɨ ɧɟ ɫɧɢɠɚɟɬɫɹ, ɚ ɟɝɨ ɨɛɴɟɦ ɭɦɟɧɶɲɚɟɬɫɹ, ɞɚ ɩɪɨɫɬɢɬ ɦɟɧɹ ɱɢɬɚɬɟɥɶ ɡɚ ɫɬɨɥɶ ɬɟɯɧɨɤɪɚɬɢɱɟɫɤɢɣɩɨɞɯɨɞɤɬɜɨɪɱɟɫɬɜɭɜɟɥɢɤɨɝɨɩɨɷɬɚ.

Ɉɱɟɜɢɞɧɨ, ɱɬɨ ɧɟɬ ɫɦɵɫɥɚ! ɩɨɥɧɨɫɬɶɸ ɩɨɜɬɨɪɹɬɶɨɞɧɚɠɞɵɫɤɚɡɚɧɧɭɸɜɪɚɡɝɨɜɨɪɟɮɪɚɡɭ ɧɟɫɤɨɥɶɤɨ ɪɚɡ. Ɍɨ ɠɟ ɫɚɦɨɟ ɨɬɧɨɫɢɬɫɹ ɢ ɤ ɤɨɦɩɶɸɬɟɪɧɨɣɢɧɮɨɪɦɚɰɢɢ.

Ɉɫɧɨɜɧɚɹ ɢɞɟɹ ɚɥɝɨɪɢɬɦɚ LZ ɫɨɫɬɨɢɬ ɜ ɬɨɦ, ɱɬɨ ɜɬɨɪɨɟ ɢ ɩɨɫɥɟɞɭɸɳɢɟ ɜɯɨɠɞɟɧɢɹ ɧɟɤɨɬɨɪɨɣ ɫɬɪɨɤɢ ɫɢɦɜɨɥɨɜ ɜ ɫɨɨɛɳɟɧɢɟ ɡɚɦɟɧɹɸɬɫɹ ɫɫɵɥɤɨɣ ɧɚ ɟɟ ɩɟɪɜɨɟ ɩɨɹɜɥɟɧɢɟ ɜ ɫɨɨɛɳɟɧɢɢ.

Szimansky. ɋɭɳɟɫɬɜɟɧɧɵɣ ɜɤɥɚɞ ɜ ɪɚɡɜɢɬɢɟ ɚɥɝɨɪɢɬɦɚɜɧɟɫɌ.ɋ.Bell.

LZSS ɹɜɥɹɟɬɫɹ ɪɚɡɜɢɬɢɟɦ LZ77 ɢ ɫɬɪɟɦɢɬɫɹ ɢɡɛɚɜɢɬɶɫɹ ɨɬ ɧɟɞɨɫɬɚɬɤɨɜ ɫɜɨɟɝɨ ɩɪɟɞɲɟɫɬɜɟɧɧɢɤɚ. LZSS ɨɬɥɢɱɚɟɬɫɹ ɨɬ LZ77 ɬɟɦ, ɤɚɤ ɩɨɞɞɟɪɠɢɜɚɟɬɫɹ ɫɤɨɥɶɡɹɳɟɟɨɤɧɨɢɤɚɤɢɟɤɨɞɵɜɵɞɚɟɬɤɨɦɩɪɟɫɫɨɪ.

LZSS, ɩɨɦɢɦɨ ɫɨɛɫɬɜɟɧɧɨ ɨɤɧɚ ɫ ɫɨɞɟɪɠɢɦɵɦ ɫɨɨɛɳɟɧɢɹ, ɩɨɞɞɟɪɠɢɜɚɟɬ ɞɜɨɢɱɧɨɟ ɞɟɪɟɜɨ ɞɥɹ ɭɫɤɨɪɟɧɢɹ ɩɨɢɫɤɚ ɫɨɜɩɚɞɟɧɢɹ. Ʉɚɠɞɚɹ ɩɨɞɫɬɪɨɤɚ, ɩɨɤɢɞɚɸɳɚɹ ɛɭɮɟɪ, ɞɨɛɚɜɥɹɟɬɫɹ ɜ ɞɟɪɟɜɨ ɩɨɢɫɤɚ, ɚ ɩɨɞɫɬɪɨɤɚ, ɩɨɤɢɞɚɸɳɚɹɫɥɨɜɚɪɶ, ɭɞɚɥɹɟɬɫɹɢɡɞɟɪɟɜɚ. Ɍɚɤɚɹ ɨɪɝɚɧɢɡɚɰɢɹ ɦɨɞɟɥɢ ɞɚɧɧɵɯ ɩɨɡɜɨɥɹɟɬ ɞɨɛɢɬɶɫɹɫɭɳɟɫɬɜɟɧɧɨɝɨɭɜɟɥɢɱɟɧɢɹɫɤɨɪɨɫɬɢɩɨɢɫɤɚ ɫɨɜɩɚɞɟɧɢɹ, ɤɨɬɨɪɚɹ, ɜ ɨɬɥɢɱɢɟ ɨɬ LZ77, ɫɬɚɧɨɜɢɬɫɹ ɩɪɨɩɨɪɰɢɨɧɚɥɶɧɚ ɧɟ ɩɪɨɢɡɜɟɞɟɧɢɸ ɪɚɡɦɟɪɨɜ ɨɤɧɚ ɢ ɩɨɞɫɬɪɨɤɢ, ɚ ɟɝɨ ɞɜɨɢɱɧɨɦɭ ɥɨɝɚɪɢɮɦɭ. ɗɬɨ ɩɨɡɜɨɥɹɟɬ ɷɤɫɩɟɪɢɦɟɧɬɢɪɨɜɚɬɶ ɫ ɛɨɥɶɲɢɦɢ ɨɤɧɚɦɢ, ɧɟɬɟɪɹɹɜɫɤɨɪɨɫɬɢɫɠɚɬɢɹ.

ɄɨɞɟɪLZSS ɢɫɩɨɥɶɡɭɟɬɨɞɧɨɛɢɬɨɜɵɣɩɪɟɮɢɤɫ, ɞɥɹ ɬɨɝɨ ɱɬɨɛɵ ɨɬɥɢɱɚɬɶ ɧɟɡɚɤɨɞɢɪɨɜɚɧɧɵɟ ɫɢɦɜɨɥɵ ɨɬ ɩɚɪ <ɫɦɟɳɟɧɢɟ, ɞɥɢɧɚ>. Ɍɚɤɢɟ ɤɨɞɵ ɩɨɡɜɨɥɹɸɬ ɩɨɥɭɱɢɬɶɫɭɳɟɫɬɜɟɧɧɵɣɜɵɢɝɪɵɲɜɪɚɡɦɟɪɟɫɠɚɬɨɝɨ ɫɨɨɛɳɟɧɢɹ.

Ɇɨɞɟɥɶɞɚɧɧɵɯ

Ʉɚɤ ɢ ɜ LZ77, ɜ ɷɬɨɦ ɚɥɝɨɪɢɬɦɟ ɢɫɩɨɥɶɡɭɟɬɫɹ ɨɛɵɱɧɵɣ ɫɢɦɜɨɥɶɧɵɣ ɛɭɮɟɪ ɞɥɹ ɯɪɚɧɟɧɢɹ ɫɨɞɟɪɠɢɦɨɝɨ ɨɤɧɚ. ȼ ɰɟɥɹɯ ɩɨɜɵɲɟɧɢɹ ɷɮɮɟɤɬɢɜɧɨɫɬɢ «ɫɤɨɥɶɠɟɧɢɹ» ɨɤɧɚ ɩɨ ɫɨɞɟɪɠɢɦɨɦɭ ɫɨɨɛɳɟɧɢɹ ɞɨɫɬɭɩ ɤ ɧɟɦɭ ɨɪɝɚɧɢɡɨɜɚɧ ɤɚɤ ɤ ɤɨɥɶɰɟɜɨɦɭ, ɢ ɪɚɡɦɟɪɨɤɧɚɤɪɚɬɟɧɫɬɟɩɟɧɢ2.

Ⱦɟɪɟɜɨ ɩɨɢɫɤɚ ɩɪɟɞɫɬɚɜɥɹɟɬ ɫɨɛɨɣ ɞɜɨɢɱɧɨɟ ɥɟɤɫɢɤɨɝɪɚɮɢɱɟɫɤɢ ɭɩɨɪɹɞɨɱɟɧɧɨɟ ɞɟɪɟɜɨ. Ʉɚɠɞɵɣ ɭɡɟɥ ɜ ɞɟɪɟɜɟ ɫɨɨɬɜɟɬɫɬɜɭɟɬ1 ɨɞɧɨɣ ɩɨɞɫɬɪɨɤɟ ɫɥɨɜɚɪɹɢɫɨɞɟɪɠɢɬɫɫɵɥɤɢɧɚɪɨɞɢɬɟɥɹɢɞɜɭɯɞɟɬɟɣ: «ɛɨɥɶɲɟɝɨ» ɢ «ɦɟɧɶɲɟɝɨ» ɜ ɫɦɵɫɥɟ ɥɟɤɫɢɤɨɝɪɚɮɢɱɟɫɤɨɝɨɫɪɚɜɧɟɧɢɹɫɢɦɜɨɥɶɧɵɯɫɬɪɨɤ.

ɇɚɩɪɢɦɟɪ, ɟɫɥɢ ɫɨɨɛɳɟɧɢɟ ɩɪɟɞɫɬɚɜɥɹɟɬ ɫɨɛɨɣ ɫɬɪɨɤɭ «ȺȻȼȽȾȿɀɁɂɄɅ», ɬɨ ɩɨɫɥɟ ɩɨɲɚɝɨɜɨɝɨ ɞɨɛɚɜɥɟɧɢɹ ɜ ɞɟɪɟɜɨ ɟɝɨ ɩɨɞɫɬɪɨɤ ɞɟɪɟɜɨ ɛɭɞɟɬ ɜɵɝɥɹɞɟɬɶɫɥɟɞɭɸɳɢɦɨɛɪɚɡɨɦ(ɪɢɫ.1).

ɄɨɞɟɪLZSS

ɂɧɢɰɢɚɥɢɡɚɰɢɹ

Ⱦɥɹ ɬɨɝɨ ɱɬɨɛɵ ɤɨɞɟɪ ɦɨɝ ɧɚɱɚɬɶ ɪɚɛɨɬɚɬɶ, ɧɟɨɛɯɨɞɢɦɨ ɡɚɝɪɭɡɢɬɶ ɛɭɮɟɪ ɨɱɟɪɟɞɧɵɦɢ ɫɢɦɜɨɥɚɦɢ ɫɨɨɛɳɟɧɢɹ ɢ ɩɪɨɢɧɢɰɢɚɥɢɡɢɪɨɜɚɬɶ ɞɟɪɟɜɨ. Ⱦɥɹ ɷɬɨɝɨɜɞɟɪɟɜɨɜɫɬɚɜɥɹɟɬɫɹɫɨɞɟɪɠɢɦɨɟɛɭɮɟɪɚ.

Ɉɫɧɨɜɧɨɣɰɢɤɥɪɚɛɨɬɵ

Ⱥɥɝɨɪɢɬɦɩɨɫɥɟɞɨɜɚɬɟɥɶɧɨɜɵɩɨɥɧɹɟɬɫɥɟɞɭɸɳɢɟɞɟɣɫɬɜɢɹ: - ɤɨɞɢɪɭɟɬɫɨɞɟɪɠɢɦɨɟɛɭɮɟɪɚ;

ɫɬɪɨɤɚ1: "ȺȻȼȽȾȿɀ" — ɫɱɢɬɵɜɚɟɬ ɨɱɟɪɟɞɧɵɟ

ɫɬɪɨɤɚ2: "ȻȼȽȾȿɀɁ"

ɫɬɪɨɤɚ3: "ȼȽȾȿɀɁɂ" ɫɢɦɜɨɥɵ ɜ ɛɭɮɟɪ, ɭɞɚɥɹɹ ɫɬɪɨɤɚ4: "ȽȾȿɀɁɂɄ" ɩɪɢ ɧɟɨɛɯɨɞɢɦɨɫɬɢ

ɫɬɪɨɤɚ5: "ȾȿɀɁɂɄɅ" ɧɚɢɛɨɥɟɟ «ɫɬɚɪɵɟ» ɫɬɪɨɤɢ ɢɡ ɫɥɨɜɚɪɹ;

— ɜɫɬɚɜɥɹɟɬ ɜ ɞɟɪɟɜɨ ɧɨɜɵɟ ɫɬɪɨɤɢ, ɫɨɨɬɜɟɬɫɬɜɭɸɳɢɟ ɫɱɢɬɚɧɧɵɦ

ɫɢɦɜɨɥɚɦ.

Ɂɚɜɟɪɲɟɧɢɟɪɚɛɨɬɵ

Ⱦɥɹ ɬɨɝɨ ɱɬɨɛɵ ɞɟɤɨɞɟɪ ɫɦɨɝ ɜɨɜɪɟɦɹ ɨɫɬɚɧɨɜɢɬɶɫɹ, ɞɟɤɨɞɢɪɭɹ ɫɠɚɬɨɟ ɫɨɨɛɳɟɧɢɟ, ɤɨɞɟɪ ɩɨɦɟɳɚɟɬ ɜ ɫɠɚɬɵɣ ɮɚɣɥ ɫɩɟɰɢɚɥɶɧɵɣ ɫɢɦɜɨɥ «ɄɈɇȿɐ ɎȺɃɅȺ» ɩɨɫɥɟ

ɬɨɝɨ, ɤɚɤ ɨɧ ɨɛɪɚɛɨɬɚɥ ɜɫɟɫɢɦɜɨɥɵɫɨɨɛɳɟɧɢɹ.

Ⱦɨɛɚɜɥɟɧɢɟɧɨɜɨɣ

ɫɬɪɨɤɢɜɞɟɪɟɜɨ

ȼɫɹ ɪɚɛɨɬɚ ɩɨ ɩɨɢɫɤɭ ɪɚɫɩɨɥɨɠɟɧɢɹ ɢ ɭɫɬɚɧɨɜɥɟɧɢɸ ɞɥɢɧɵ ɦɚɤɫɢɦɚɥɶɧɨɝɨ ɫɨɜɩɚɞɟɧɢɹ

ɫɨɞɟɪɠɢɦɨɝɨ ɫɥɨɜɚɪɹ ɫ ɛɭɮɟɪɨɦ ɩɪɨɢɫɯɨɞɢɬ ɜ ɩɪɨɰɟɫɫɟɞɨɛɚɜɥɟɧɢɹɜɞɟɪɟɜɨɧɨɜɨɣɫɬɪɨɤɢ.

ɉɪɢ ɞɨɛɚɜɥɟɧɢɢ ɫɬɪɨɤɢ ɜ ɞɟɪɟɜɨ ɚɥɝɨɪɢɬɦ ɩɨɫɥɟɞɨɜɚɬɟɥɶɧɨ ɩɟɪɟɦɟɳɚɟɬɫɹ ɨɬ ɤɨɪɧɹ ɞɟɪɟɜɚ ɤ ɟɝɨ ɥɢɫɬɭ, ɤɚɠɞɵɣ ɪɚɡ ɨɫɭɳɟɫɬɜɥɹɹ ɥɟɤɫɢɤɨɝɪɚɮɢɱɟɫɤɨɟ ɫɪɚɜɧɟɧɢɟɧɨɜɨɣɫɬɪɨɤɢɢɭɡɥɚɞɟɪɟɜɚ. ȼɡɚɜɢɫɢɦɨɫɬɢ ɨɬ ɪɟɡɭɥɶɬɚɬɚ ɫɪɚɜɧɟɧɢɹ ɜɵɛɢɪɚɟɬɫɹ ɛɨɥɶɲɢɣ ɢɥɢ ɦɟɧɶɲɢɣɪɟɛɺɧɨɤɷɬɨɝɨɭɡɥɚɢɡɚɩɨɦɢɧɚɟɬɫɹɞɥɢɧɚ ɫɨɜɩɚɞɟɧɢɹɫɬɪɨɤɢɩɨɥɨɠɟɧɢɟɬɟɤɭɳɟɝɨɭɡɥɚ.

ȿɫɥɢ ɜ ɪɟɡɭɥɶɬɚɬɟ ɫɪɚɜɧɟɧɢɹ ɨɤɚɡɵɜɚɟɬɫɹ, ɱɬɨ ɫɨɞɟɪɠɢɦɨɟɛɭɮɟɪɚɢ ɫɬɪɨɤɚ, ɧɚɤɨɬɨɪɭɸ ɫɫɵɥɚɟɬɫɹ ɬɟɤɭɳɢɣ ɭɡɟɥ, ɜ ɬɨɱɧɨɫɬɢ ɫɨɜɩɚɞɚɸɬ, ɬɨ ɫɫɵɥɤɢ ɜ ɬɟɤɭɳɟɦ ɭɡɥɟ ɨɛɧɨɜɥɹɸɬɫɹ ɬɚɤ, ɱɬɨɛɵ ɨɧɢ ɭɤɚɡɵɜɚɥɢɧɚɛɭɮɟɪ, ɢɩɪɨɰɟɞɭɪɚɞɨɛɚɜɥɟɧɢɹɫɬɪɨɤɢɜ ɞɟɪɟɜɨɡɚɜɟɪɲɚɟɬɫɹ.

ȿɫɥɢ ɪɟɛɟɧɨɤ ɬɟɤɭɳɟɝɨ ɭɡɥɚ, ɜɵɛɪɚɧɧɵɣ ɞɥɹ ɨɱɟɪɟɞɧɨɝɨ ɲɚɝɚ, ɨɬɦɟɱɟɧ ɤɚɤ ɧɟɫɭɳɟɫɬɜɭɸɳɢɣ, ɨɫɬɚɟɬɫɹɡɚɩɨɥɧɢɬɶɟɝɨɫɨɨɬɜɟɬɫɬɜɭɸɳɟɣɫɫɵɥɤɨɣɢ ɡɚɜɟɪɲɢɬɶɪɚɛɨɬɭ.

ɇɭɠɧɨ ɨɬɦɟɬɢɬɶ, ɱɬɨ ɩɪɢ ɨɤɨɧɱɚɧɢɢ ɪɚɛɨɬɵ ɩɪɨɰɟɞɭɪɟ ɞɨɛɚɜɥɟɧɢɹ ɫɬɪɨɤɢ ɢɡɜɟɫɬɧɵ ɢ ɫɦɟɳɟɧɢɟ, ɢ ɞɥɢɧɚ ɧɚɢɛɨɥɶɲɟɝɨ ɫɨɜɩɚɞɟɧɢɹ, ɢ ɞɥɹ ɷɬɨɝɨ ɧɟ ɩɨɬɪɟɛɨɜɚɥɫɹ ɩɨɥɧɵɣ ɩɟɪɟɛɨɪ ɜɫɟɯ ɜɨɡɦɨɠɧɵɯ ɜɚɪɢɚɧɬɨɜɫɨɜɩɚɞɟɧɢɹ.

ɍɞɚɥɟɧɢɟɫɬɪɨɤɢɢɡɞɟɪɟɜɚ

ɉɪɢ ɭɞɚɥɟɧɢɢ ɭɡɥɚ ɢɡ ɞɟɪɟɜɚ ɜɨɡɦɨɠɧɵ ɞɜɚ ɜɚɪɢɚɧɬɚ.

ȿɫɥɢ ɭɡɟɥ ɢɦɟɟɬ ɧɟ ɛɨɥɟɟ ɨɞɧɨɝɨ ɪɟɛɟɧɤɚ, ɬɨ ɭɞɚɥɟɧɢɟ ɭɡɥɚ ɨɫɭɳɟɫɬɜɥɹɟɬɫɹ ɩɪɨɫɬɵɦ ɢɫɩɪɚɜɥɟɧɢɟɦ ɫɫɵɥɨɤ «ɪɨɞɢɬɟɥɶ-ɪɟɛɟɧɨɤ». ȿɫɥɢ ɭɡɟɥ ɢɦɟɟɬ ɞɜɨɢɯ ɞɟɬɟɣ, ɬɨ ɧɟɨɛɯɨɞɢɦɵ ɞɪɭɝɢɟ ɞɟɣɫɬɜɢɹ. Ⱦɥɹ ɷɬɨɝɨ ɧɚɣɞɟɦ ɫɥɟɞɭɸɳɢɣ ɦɟɧɶɲɢɣ ɭɡɟɥ ɜ ɞɟɪɟɜɟ, ɭɞɚɥɢɦ ɟɝɨ ɢɡ ɞɟɪɟɜɚ ɢ ɡɚɦɟɧɢɦ ɢɦ ɬɟɤɭɳɢɣɭɞɚɥɹɟɦɵɣ ɭɡɟɥ. ɋɥɟɞɭɸɳɢɣ ɦɟɧɶɲɢɣɭɡɟɥ ɧɚɯɨɞɢɬɫɹ ɜɵɛɨɪɨɦ ɦɟɧɶɲɟɝɨ ɪɟɛɟɧɤɚ ɢ ɩɨɫɥɟɞɭɸɳɢɦ ɩɟɪɟɦɟɳɟɧɢɟɦ ɨɬ ɧɟɝɨ ɩɨ ɞɟɪɟɜɭ ɞɨ ɥɢɫɬɚɩɨɛɨɥɶɲɢɦɜɟɬɜɹɦ.

ȾɟɤɨɞɟɪLZSS

Ⱥɥɝɨɪɢɬɦ LZSS, ɜɨɨɛɳɟ ɝɨɜɨɪɹ, ɹɜɥɹɟɬɫɹ ɨɱɟɧɶ ɚɫɢɦɦɟɬɪɢɱɧɵɦ. ȿɫɥɢ ɩɪɨɰɟɞɭɪɚ ɫɠɚɬɢɹ ɞɨɫɬɚɬɨɱɧɨ ɫɥɨɠɧɚ ɢ ɫɨɜɟɪɲɚɟɬ ɛɨɥɶɲɨɣ ɨɛɴɟɦ ɪɚɛɨɬɵ ɩɪɢ ɨɛɪɚɛɨɬɤɟ ɤɚɠɞɨɝɨ ɫɢɦɜɨɥɚ ɫɠɢɦɚɟɦɨɝɨ ɫɨɨɛɳɟɧɢɹ, ɬɨ ɞɟɤɨɞɟɪ LZSS ɬɪɢɜɢɚɥɶɧɨɩɪɨɫɬɢɦɨɠɟɬɪɚɛɨɬɚɬɶɫɨɫɤɨɪɨɫɬɶɸ, ɩɪɢɛɥɢɠɚɸɳɟɣɫɹ ɤ ɫɤɨɪɨɫɬɢ ɩɪɨɰɟɞɭɪɵ ɨɛɵɱɧɨɝɨɤɨɩɢɪɨɜɚɧɢɹɢɧɮɨɪɦɚɰɢɢ.

Ⱦɟɤɨɞɟɪ ɱɢɬɚɟɬ ɨɞɢɧ ɛɢɬ ɫɠɚɬɨɣ ɢɧɮɨɪɦɚɰɢɢ ɢ ɪɟɲɚɟɬ — ɷɬɨ ɫɢɦɜɨɥ ɢɥɢ ɩɚɪɚ <ɫɦɟɳɟɧɢɟ, ɞɥɢɧɚ>. ȿɫɥɢ ɷɬɨ ɫɢɦɜɨɥ, ɬɨ ɫɥɟɞɭɸɳɢɟ 8 ɛɢɬɨɜ ɜɵɞɚɸɬɫɹ ɤɚɤ ɪɚɫɤɨɞɢɪɨɜɚɧɧɵɣ ɫɢɦɜɨɥ ɢ ɩɨɦɟɳɚɸɬɫɹ ɜ ɫɤɨɥɶɡɹɳɟɟ ɨɤɧɨ. ɂɧɚɱɟ, ɟɫɥɢ ɷɬɨ ɧɟ ɡɚɤɨɞɢɪɨɜɚɧɧɵɣɤɨɧɟɰɮɚɣɥɚ, ɬɨɫɨɨɬɜɟɬɫɬɜɭɸɳɟɟɤɨɥɢɱɟɫɬɜɨ ɫɢɦɜɨɥɨɜ ɫɥɨɜɚɪɹ ɩɨɦɟɳɚɟɬɫɹ ɜ ɨɤɧɨ ɢ ɜɵɞɚɟɬɫɹɜɪɚɫɤɨɞɢɪɨɜɚɧɧɨɦɜɢɞɟ.

ɉɨɫɤɨɥɶɤɭɷɬɨɜɫɟ, ɱɬɨ ɞɟɥɚɟɬ ɞɟɤɨɞɟɪ, ɩɨɧɹɬɧɨ, ɩɨɱɟɦɭ ɩɪɨɰɟɞɭɪɚ ɞɟɤɨɞɢɪɨɜɚɧɢɹ ɪɚɛɨɬɚɟɬ ɬɚɤ ɛɵɫɬɪɨ.

Ɂɚɤɥɸɱɟɧɢɟ

ɇɟɫɦɨɬɪɹ ɧɚ ɬɨ ɱɬɨ ɫɟɦɚɧɬɢɤɚ ɚɥɝɨɪɢɬɦɨɜ, ɨɩɢɫɚɧɧɵɯ ɜ ɫɬɚɬɶɟ, ɥɭɱɲɟ ɜɫɟɝɨ ɪɚɫɤɪɵɜɚɟɬɫɹ ɧɚ ɩɪɢɦɟɪɟ ɬɟɤɫɬɨɜɨɣ ɢɧɮɨɪɦɚɰɢɢ, ɩɪɚɤɬɢɤɚ ɩɨɤɚɡɵɜɚɟɬ, ɱɬɨ ɨɧɢ ɬɚɤ ɠɟ ɯɨɪɨɲɨ ɪɚɛɨɬɚɸɬ ɫ ɥɸɛɨɣ, ɜ ɩɪɢɧɰɢɩɟ ɫɠɢɦɚɟɦɨɣ, ɢɧɮɨɪɦɚɰɢɟɣ. ɗɬɢ ɚɥɝɨɪɢɬɦɵ ɩɨ ɫɜɨɟɣ ɩɪɢɪɨɞɟ ɹɜɥɹɸɬɫɹ ɚɞɚɩɬɢɜɧɵɦɢ, ɱɬɨ ɫɪɚɡɭ ɫɧɢɦɚɟɬ ɰɟɥɵɣ ɪɹɞ ɩɪɨɛɥɟɦ. Ɍɚɤ ɤɚɤ ɨɩɢɫɚɧɧɵɟ ɚɥɝɨɪɢɬɦɵ ɧɟ ɹɜɥɹɸɬɫɹ ɡɚɩɚɬɟɧɬɨɜɚɧɧɵɦɢ, ɬɨ ɜɵ ɦɨɠɟɬɟ ɢɫɩɨɥɶɡɨɜɚɬɶ ɩɪɨɝɪɚɦɦɭ, ɩɪɢɜɟɞɟɧɧɭɸ ɜ ɥɢɫɬɢɧɝɟ, ɜɤɨɦɦɟɪɱɟɫɤɢɯ ɰɟɥɹɯ. ȿɫɥɢ

ɜɵ «ɫɤɥɟɢɬɟ» ɜɵɯɨɞ LZSS ɫɨ ɜɯɨɞɨɦ ɚɥɝɨɪɢɬɦɚ ɚɞɚɩɬɢɜɧɨɝɨ ɤɨɞɢɪɨɜɚɧɢɹ ɏɚɮɮɦɟɧɚ, ɨɩɢɫɚɧɧɨɝɨ ɜ ɫɬɚɬɶɟ [7], ɬɨ ɩɨɥɭɱɢɬɟ ɩɪɨɝɪɚɦɦɭ, ɷɤɜɢɜɚɥɟɧɬɧɭɸ PKZIP ɢɥɢ LHA ɩɨ ɫɬɟɩɟɧɢ ɫɠɚɬɢɹ. •

Ɋɟɤɨɦɟɧɞɭɟɦɚɹ ɥɢɬɟɪɚɬɭɪɚ

1.Ziv J., Lempel A. An Universal Algorithm forSequential Data Compression// IEEE Transactions on Information Theory. - 1977. - Vol. 23. - ʋ 3.

2.Ziv J., Lempel A. Compression of Individual Sequences via Variable Rate Coding// IEEE Transactions on Information Theory, - 1978. -Vol. 23. - ʋ 3.

3.Storer J. A., Szymanski Ɍ. G. Data Compression via Textual Substitution// Journal of the ACM. - 1982. -Vol.

29.-ʋ4.

4.Bell T. C. Better OPM/L Compression// IEEE Transactions on Communications. - 1986. -Vol. 34. -P. p. 1176-1182.

5.Storer J. A. Data Compression: Methods and Theory. -USA: Computer Science Press, 1988.

6.Nelson M. The Data Compression Book. - USA: M&T Publishing, 1991.

7.Ⱦ. Ɇɚɫɬɪɸɤɨɜ. ɋɠɚɬɢɟ ɩɨ ɏɚɮɮɦɟɧɭ// Ɇɨɧɢɬɨɪ. - 1993. -ʋ7-8.

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ȼɫɥɟɞɭɸɳɟɦɧɨɦɟɪɟ

Ⱥɥɝɨɪɢɬɦ LZW, ɩɨɹɜɢɜɲɢɣɫɹ ɜ 1984 ɝɨɞɭ, ɫɬɚɥ ɩɟɪɜɵɦ ɩɪɨɦɵɲɥɟɧɧɵɦ ɫɬɚɧɞɚɪɬɨɦ ɧɚ ɫɠɚɬɢɟ ɢɧɮɨɪɦɚɰɢɢ. ɇɚ ɟɝɨ ɨɫɧɨɜɟ ɩɨɫɬɪɨɟɧ ɬɟɥɟɤɨɦɦɭɧɢɤɚɰɢɨɧɧɵɣ ɫɬɚɧɞɚɪɬ V. 42bis, ɨɧ ɢɫɩɨɥɶɡɭɟɬɫɹ ɞɥɹ ɫɠɚɬɢɹ ɝɪɚɮɢɱɟɫɤɢɯ ɨɛɪɚɡɨɜ ɜ ɮɚɣɥɚɯ ɮɨɪɦɚɬɚ GIF. ɏɨɬɹ LZW ɹɜɥɹɟɬɫɹ ɩɚɬɟɧɬɨɜɚɧɧɵɦ ɚɥɝɨɪɢɬɦɨɦ (ɤɨɦɩɚɧɢɹ Unisys), ɨɧ ɧɟɫɨɦɧɟɧɧɨ ɦɨɠɟɬ «ɩɪɢɝɨɞɢɬɶɫɹ ɜ ɯɨɡɹɣɫɬɜɟ».