The proposed architecture accelerates the LZ77 compression algorithm and supports the throughput-first (TF) and compression ratio-first (CF) modes by changing the degree of parallelism of comparison operations performed during the compression process. C, at the expense of */. It was patented, but it entered the public domain in 2004. We are interested in the best compression ratios for Lempel-Ziv compression schemes. The lz77 compression algorithm replaces duplicate bit positions regarding their previous positions. Features Coded in 100% 32bit x86 assembly language for maximum performance and minimum size. Many variations of LZ surfaced in the past thirty years, and a detailed description of them all would be quite useful for historical reference. 7 compared to the total ratio of 2. This is a data compression algorithm that improves on LZ77. Such collections are extremely compressible but classical self-indexes fail to capture that. This process of compression is done by including a method that will keep an eye on. Constantly learning. Refresh the page, check Medium ’s site status, or find something interesting to read. This is called lossy compression. LZ77 compression is a well known lossless technique and it is widely used in pop-ular tools. Decompression only Compression and decompression. 6GB with the default lz4). Its power comes from its simplicity, speed, and decent compression rates. The compression ratio was also improved compared with directly using LZ77 algorithm. dictionary compression method · one-pass compression method · adaptive compression. Long: skip_existing (Optional) Specify whether to build pyramids only when they are missing or regenerate them even if they. LZ77 achieves data compression via a sliding window mechanism: bytes from a look-ahead buffer are shifted one by one into a search buffer. A simplified implementation of the LZ77 compression algorithm in python. lzma command line tool has a similar interface to gzip (1) and bzip2 (1) and is intended to make. It has 5 star(s) with 3 fork(s). I'd like to get some feedback on my code's quality and also information about mistakes and dubious places in my program (if I have any). The operation of the LZ77 IP is similar to that of a Content-addressable Memory (CAM), which is a well known technique to implement dictionaries in. compression ratio is 3. While the solution bears similarity to known algorithms, it offers significantly higher compression ratios at compression speed over an order of magnitude greater. compression ratio with LZMA2 use 1 or 2 CPU threads. Then, the LZ77 algorithm is used to compress the six final files. Typical compression ratios are between 2:1 and 5:1. See data compression , codec examples , JPEG , MPEG and MP3. It was selected by the ITU-T as the basis for Recommendation V. The results also showed that the Deflate algorithm can compress text files and generates an average compression ratio of 38. 4x speedup in compression time was observed. In executable compression, we can consider LZ an umbrella term for LZ77, LZSS, LZB, LZH, LZARI, and any other algorithms inspired by those designs. vf dw. compression ratio is 3. LZ77 Compression – Compression Rates. The Lempel-Ziv-Welch (LZW) algorithm provides loss-less data compression. The LZ4 algorithm represents the data as a series of sequences. The compression ratio was also improved compared with directly using LZ77 algorithm. We then build the rst self-index based on LZ77 (or LZ-End) compression, which in addition. We introduce the first self-index based on the Lempel-Ziv 1977 compression format (LZ77). 2 What is the smallest number of phrases in the LZ78 parse of S?. • They are also known as LZ1 and LZ2 respectively. As gzip uses LZ77 (and Huffman encoding), I decided to start by . communities including Stack Overflow, the largest, most trusted online community for developers learn, share their knowledge, and build their careers. Show more Show more Learn in 5 Minutes:. For the binary representation, the commonly used values are:. , worse) compression ratio than the similar LZO algorithm, which in turn is. Compression and decompression algorithms in the secure messaging application are implemented using LZSS [14] library - a variant of LZ77 [34]. Show more Show more Learn in 5 Minutes:. LZSS was described in article "Data compression via textual substitution" published in Journal of the ACM (1982, pp. 9bits \\slash base and even lower. [2] They are also known as LZ1 and LZ2 respectively. However, you can limit the RAM usage in it. Choose a language:. Use the LZ77 algorithm to compress the string "abbdacdbbbbabba" and calculate the compression ratio. Example 2. Embodiments determine an initial run from input data. This mode favours processing speed over compression ratio. It is used in popular compression. compress by using LZ77 compression method in the second level and after that form the grid variables with size 3 to hold the 100 characters. Hardware accelerators are being considered as important architectural components in the context of datacenter customization to achieve high performance and low power. It's a fit for applications where you want compression that's very cheap: for example, you're trying to make a network or on-disk format more compact but can't afford to spend a bunch of CPU time on compression. Adaptive Huffinan Compression Ratios. DEFLATE uses a combination of the LZ77 algorithm and Huffman coding. Compression algorithm details While it is the intent of this document to define the "deflate" compressed data format without reference to any particular compression algorithm, the format is related to the compressed formats produced by LZ77 (Lempel-Ziv 1977, see reference below); since many variations of LZ77 are patented, it is strongly. It is also sometimes used for network data compression. niques, in terms of compression efficiency, especially under limited decoder buffer size, as required for hardware implementation. Lempel-Ziv, commonly referred to as LZ77/LZ78 depending on the variant, is one of the oldest, most simplistic, and widespread compression algorithms out there. A hardware data compressor. the compression ratio, and decoder bufier size for C4, which constitutes a signiflcant portion of the decoder implementation complexity. lzbench is an in-memory benchmark of open-source LZ77/LZSS/LZMA compressors. Initially, all nodes are leaf nodes, which contain the symbol itself, the weight. We suggest an adaptive encoding scheme, which optimizes the parameters block by block, and base the compression performance on the optimality proof of LZ77 when applied to blocks [25]. The compression ratio was also improved compared with directly using LZ77 algorithm. A character to replace invisible symbol. An Optimizing Hybrid LZ77 RLE Data Compression Program, aka Improving Compression Ratio for Low-Resource Decompression Short: Pucrunch is a Hybrid LZ77 and RLE compressor, uses an Elias Gamma Code for lengths, mixture of Gamma Code and linear for LZ77 offset, and ranked RLE bytes indexed by the same Gamma Code. I'd like to get some feedback on my code's quality and also information about mistakes and dubious places in my program (if I have any). LZ77, a lossless data-compression algorithm, was created by Lempel and Ziviv in 1977. LZ77 compressor and decompressor in C++ Ask Question Asked 2 years, 5 months ago Modified 2 years, 5 months ago Viewed 884 times 6 I've written working LZ77 algorithm implementation which uses linked lists (they help to look for matching substrings faster). Uses no extra memory in. A first search engine determines a second run that includes the repeating data at a. Compression Spring Compression Spring Screw #5-40 x 7/16 Screw #6-32 x 21/32 Throttle Link Controt Knob Screw 1/4-20 x 1. 1 What is the smallest number of phrases in the LZ77 parse of S?. so it must be considered aspects such as compression ratio, space-saving,. Linux Reader™ shows you all the available files, including pictures, videos, documents, and other files. The Lempel-Ziv 1977 Algorithm (LZ77) not yet coded already coded. Fork 2. Each has. How the LZ77 works. Algorithms Digital image compression techniques lzw coding in digital image processing 1 ] Digital corso app image. À retenir Une sliding window (fenêtre glissante) c'est un historique des derniers octets. pressors, which achieves compression ratios close to those of LZ77 but per-forms much faster at extracting arbitrary text substrings. I have written z80 code to decompress using lz77 algorithm (with sliding window of 256 bytes). In general, the additional blocking and heuristics that GZIP uses give it better compression ratios than DEFLATE. Compression ratio Binary representation. 1 times. I tried other ratios, but 12:4 seemed. It is the algorithm of the widely used Unix file compression utility compress and is used in the GIF image format. A collection of resources and posts to help people understand compression algorithms. 5 bits per character, however the entropy of English text . The first number represents compression power where the second (usually just "1") refers to the total size of the uncompressed data. The Idea relies on reoccurring patterns to save data space. The Compression API exposes an interface that enables the developer to set or query the values of these properties. vf dw. The proposed architecture accelerates the LZ77 compression algorithm and supports the throughput-first (TF) and compression ratio-first (CF) modes by changing the degree of parallelism of comparison operations performed during the compression process. LZ77 algorithms achieve compression by replacing repeated occurrences of data with references to a single copy of that data existing earlier in the uncompressed data stream. 6 GB/s. LZJH Any of the above algorithms may be useful depending on the desired compression ratio, processing and memory . Some LZ77 compression utilities for the handy hands-on developer in search for a few less bytes of I/O. Too Difficult! 154. Compression usually. For any xed stationary source the LZW algorithm performs just as well. LZ77 In this post we are going to explore LZ77, a lossless data-compression algorithm created by Lempel and Ziv in 1977. Decompression only Compression and decompression. Deflate (RFC 1951) is used for its compression algorithm. The y-axis represents the compression ratio of each item. Current program version compresses and decompresses files (. Each sequence begins with a one-byte token that is broken into two 4-bit fields. A lower ratio means less memory and I/O usages. For the airport with the ICAO code "LZMA", see Martin Airport (Slovakia). Many variations of LZ surfaced in the past thirty years, and a detailed description of them all would be quite useful for historical reference. Performance: Throughput: 8 input bytes per cycle clock; Compression ratio: 1. The LZ4 algorithm represents the data as a series of sequences. The data can be produced or consumed, even for an arbitrarily long sequentially presented input data. LZ4 - LZ77-type compressor with a fixed, byte-oriented encoding and no Huffman coding pass {new ROOT default} ZSTD - dictionary-type algorithm (LZ77) with large search window and fast. On small data, the encoded part can be larger than the original data. This algorithm is widely spread in our current systems since, for instance, ZIP and GZIP are based on LZ77. It uses a variable dictionary size. Integrity checks performed with the CRC-32 or the ADLER 32 checksums. 3 Tuning Compression for InnoDB Tables. Yet, extracting an arbitrary substring is expensive, with cost bounded only by the col-lection size in general. Compression ratio Binary representation. but compression ratio is ruined as long-range repetitions are not captured. The following sections will explain these specific techniques, and then how the compression and decompression operate. Set the coding position to the beginning of the input stream. LZ4 is built to compress fast, at hundreds of MB/s per core. The data can be produced or consumed, even for an arbitrarily long sequentially presented input data. LZSS was described in article "Data compression via textual substitution" published in Journal of the ACM (1982, pp. Some experiments indicate that the compression ratio is 1. on passe de 307 octets à 62 octets (!). Abstract: In a multimedia system, one is required to handle, store and transmit a lot of data. However, lossless methods have relatively low compression ratios. For best 3. Thereafter, the tokenized message can optionally be compressed further utilizing a standard compression algorithm, such as Lempel-Ziv 1977 (LZ77), to attain a substantial compression ratio. First off let me note that we end up trading off compression ratio for processing speed. The biggest advantage of this algorithm is fast, small memory. Zlib Publisher Description. LZ77 can be used for any data type. bmc obgyn residents. Choose a language:. Lempel-Ziv, commonly referred to as LZ77/LZ78 depending on the variant, is one of the oldest, most simplistic, and widespread compression algorithms out there. A simplified implementation of the LZ77 compression algorithm in python. 2 Burrows-Wheeler Transform Burrows and Wheeler [2] presented in 1994 a block-sorting lossless data compression algorithm whose speed was comparable to algorithms based on LZ77 techniques and compression ratios were close to the best known compression ratios. ALGORITHMS ANALYSIS C: Total no of Matching (offset=Matching Length) CR: Compression ratio Op LZ77: Optimized LZ77 Algorithm LZ77: Conventional LZ77 Algorithm D: % Difference between conventional LZ77 and Optimized LZ77= (Op LZ77 - LZ77) / LZ77 Max. In this work we detail a scalable fully pipelined FPGA accelerator that performs LZ77 compression and static Huffman encoding at rates up to 5. The Lempel-Ziv 77 compression (LZ77) is one of the most successful lossless compression algorithms to date. The compressed data within the zlib datastream is stored as a series of blocks, each of which can represent raw (uncompressed) data, LZ77-compressed data encoded with fixed Huffman codes, or LZ77-compressed data. It has 5 star(s) with 3 fork(s). For best 3. View a sample solution. Uses no extra memory in. Suppose storing an image made up of a square array of 256. It is the weighted average of the number of bits required to encode the symbols of a message:. If you are interested to learn about Huffman encoding of lossless image compression then please visit dataqoil. The process of compression can be divided in 3 steps:Find the longest match of a string that starts at the current. the amount of compression that can be obtained with lossless compression. We are interested in the best compression ratios for Lempel-Ziv compression schemes. The results showed that algorithm proposed by Borici and Arber is the best in case of compression ratio, as it provides better compression ratio in. Michael Dipperstein: LZSS (LZ77) Discussion and Implementation. LZSS is still used in many popular archive formats, the best known of which is RAR. I've written working LZ77 algorithm implementation which uses linked lists (they help to look for matching substrings faster). We used compression level 5, the same compression level we currently use for dynamic compression on our edge, and tested on a Intel Core i7-7820HQ CPU. Calculate data compression rate or data size before and after compression. 0 Result : Compressed_Data (1. On small data, the encoded part can be larger than the original data. A BIT ABOUT SLIDING WINDOW COMPRESSION (LZ77). The LZ77 Compression Algorithm is used to analyze input data and determine how to reduce the size of that input data by replacing redundant information with metadata. A fully pipelined compression accelerator for the Lempel-Ziv (LZ) compression algorithm is presented, verified by using FPGA and fabricated using 65nm CMOS technology. It's a fit for applications where you want compression that's very cheap: for example, you're trying to make a network or on-disk format more compact but can't afford to spend a bunch of CPU time on compression. The main features of 7z format: Open architecture High compression ratio. The LZ77 compression algorithm is used to analyze input data and determine how to reduce the size of that input data by replacing redundant information with metadata. the compression ratio, and decoder bufier size for C4, which constitutes a signiflcant portion of the decoder implementation complexity. This arguably would create the best compression possible. The folder containing the entire dataset (20 files) is reduced from 38,065,903 bytes (38 MB) to 8,841,139 bytes (8. Learn more about compression ratio, lz77. LZMA (Lempel-Ziv-Markov chain-Algorithm) is an improved version of famous LZ77 compression algorithm. [LZ77] J. Other algorithms has better compression ratios but they only work on ram (no vram). Typically, this algorithm yields better compression than the one used by compress. LZMA SDK includes: C++ source code of LZMA Encoder and Decoder Using the highest rate 9, 65 MB RAM is needed. Many variations of LZ surfaced in the past thirty years, and a detailed description of them all would be quite useful for historical reference. As we had experimented earlier in Java we could discover every possible matching sequence for a block of data and then analyze those matches selecting the optimum set. LZ77 and LZ78 are the two lossless data compression algorithms published in papers by Abraham Lempel and Jacob Ziv in 1977 and 1978. LZSS had the second fastest decompression time and used the lowest CPU decompression time for test file1. 1 Legal Issues; 2. This version operates on 1MB block data per engine as this is suitable for use cases where raw data is over >100MB and compression ratio is over 2. – Lempel-Ziv (LZ77, Gzip, LZ78, LZW, Unix compress) • Synchronization • Compressing inverted files • Compression in block-level retrieval. LZMA is default and general compression method of 7z format. It is also sometimes used for network data compression. It is derived from the LZ77 compression algorithm. This article introduces a new DNA sequence compression algorithm which is based on LUT and LZ77 algorithm. For any xed stationary source the LZW algorithm performs just as well. The second field represents the number of bytes to copy from the already decoded output buffer (with 0. LZ77 In this post we are going to explore LZ77, a lossless data-compression algorithm created by Lempel and Ziv in 1977. The benchmark currently consists of 36 datasets,. This paper presents hardware implementations for the LZ77 encoders and Huffman encoders that form the basis for a full hardware implementation of a GZIP encoder. The LZNT1 buffer is structured as a series of chunks that can be independently decompressed. Compared to gzip and zopfli, brotli boasts a far more superior compression ratio (according to a Google study, Brotli came out with a 20-26% increase in compression ratio compared to Zopli. Because lossless compression retains all the pixel values, it can only compress raster data at a low file-size ratio (such as 2:1 or 3:1, depending on the data). "gzip" uses the Lempel-Ziv coding (LZ77) algorithm to compress data, and is known for its high compression ratio and fast compression speed. Dual Rated for Aluminum or Copper Conductors. Simply experiment with various compression methods (zstd, xz, lz4, etc. Compression Spring Compression Spring Screw #5-40 x 7/16 Screw #6-32 x 21/32 Throttle Link Controt Knob Screw 1/4-20 x 1. LZ77 compression and Huffman encoding. View Answer. The Lempel-Ziv 77 compression (LZ77) is one of the most successful lossless compression algorithms to date. incall massage los angeles
The second field represents the number of bytes to copy from the already decoded output buffer (with 0. . Lz77 compression ratio
Log In My Account wi. WinZip 10 or newer and 7Zip. Show more Show more Learn in 5 Minutes:. Usage notes. jumping-off point as it’s a basic evolution of LZ77 and can be implemented very easily while achieving a respectable compression ratio. To prove this method first we have to give its new algorithm and after completing the algorithm we have compress and de-compress to check the character and at last it achieves the compression ratio 1. Each instruction starts with a 1-byte opcode, 2-byte opcode, or 3-byte opcode. 6 GB/s. Many variations of LZ surfaced in the past thirty years, and a detailed description of them all would be quite useful for historical reference. In this paper, we propose a FPGA bitstream compression method based on LZ77 algorithm and Bitmask-based Compression(BMC) Technique. The LZ77 sequences are then efficiently encoded into a binary stream by using Huffman encoding. While the solution bears similarity to known algorithms, it offers significantly higher compression ratios at compression speed over an order of magnitude greater. LZ77 variants don't improve a lot on compression ratio, but they do improve on speed instead. 2Xenergy savings against multi-core state-of-the-art. LZ77 (the default) is a lossless compression that preserves all raster cell values. 26 Feb 2016. It has become increasingly important to most computer networks, as the. LZNT1 varies the number of bits used to encode length and distance, whereas the sizes of the Plain LZ77-encoded fields are fixed. Compression Ratios; Unix Magic Numbers; Raisin; Resources;. Each sequence begins with a one-byte token that is broken into two 4-bit fields. Compression Ratio: Since we are dealing with compressed indexes it is useful to have an idea of the compressibility of the texts using general-purpose compressors. [20] uses di erent dictionaries for di erent length strings enabling parallel lookup for LZW. Enter text to encode. 2 Compression Ratios for Lempel-Ziv Let S be a string of length n. The block sort-ing compression became famous now for the reason of a good balance of compression speed and ratio. If a property is required for both compression and decompression, the default values will be. */ /* This program uses more efficient code to delete strings from */ /* the sliding dictionary compared to PROG1. Consider Fig. The process of compression can be divided in 3 steps:Find the longest match of a string that starts at the current. I’ve chosen some usual compression methods, here is a short digest (more or less copy&paste from the man pages): gzip: uses Lempel-Ziv coding (LZ77), cmd: tar czf $1. 9bits /base and even lower. 9bits /base and even lower. In particular, this is the case for the LZ77 technique and its derivatives, where matches can often be described in more than one way. The LZ4 algorithms aims to provide a good trade-off between speed and compression ratio. LZ77 + Huffman coding Good compression ratio, slow Intel® QuickAssist Technology supports:. Improved LZ77 compression algorithm. LZ77 and LZ78 Compression Algorithms • LZ77 and LZ78 are the two lossless data compression algorithms published in papers by Abraham Lempel and Jacob Ziv in 1977 and 1978. The benchmark currently consists of 36 datasets, tested against 40 codecs at every compression level they offer. Micromachines 2021, 12, 145 3 of 11 LZ77 algorithm. Data Compression LZ77 Jens M leer University t Stuttgart 2008-11-25 Outline Introduction Principle of dictionary. CiteSeerX - Document Details (Isaac Councill, Lee Giles, Pradeep Teregowda): Many data compression techniques allow for more than one way to encode the compressed form of data. The lossless compression algorithm LZ78 was published in 1978 by Abraham Lempel and Jacob Ziv and then modified by Terry Welch in 1984. LZ77, released in 1977, is the base of many other lossless compression algorithms. You can read a complete description of it in the Wikipedia article on the subject. 0 Result : Compressed_Data (1. Deflate (RFC 1951) is used for its compression algorithm. Many popular compression programs, such as zip, gzip and 7zip, use this. This article introduces a new DNA sequence compression algorithm which is based on LUT and LZ77 algorithm. It was selected by the ITU-T as the basis for Recommendation V. This algorithm generally yields a better compression. Using a lookahead buffer at a certain position, the longest match is found from a fixed size window of data history. Image Compression In Python: Run Length Encoding 8 minute read Image Compression (Teaser Image taken from here. This algorithm generally yields a better compression. Refresh the page, check Medium ’s site status, or find something interesting to read. The methods of improving the compression ratio of LZ77 family data compression algorithms. But on large data such as Victor Hugo’s Les Misérables (Volume 1): Original file: 710 kilobytes Compressed file: 420 kilobytes Either 40% compression. DEFLATE is a combination of dictionary compression (LZ77) and Huffman coding. Snapshots are a lot easier to selectively recover files from and they also take a lot less space. LZ77 compressor and decompressor in C++ Ask Question Asked 2 years, 5 months ago Modified 2 years, 5 months ago Viewed 884 times 6 I've written working LZ77 algorithm implementation which uses linked lists (they help to look for matching substrings faster). Compression ratio Binary representation For the binary representation, the commonly used values are:. Compression Spring Compression Spring Screw #5-40 x 7/16 Screw #6-32 x 21/32 Throttle Link Controt Knob Screw 1/4-20 x 1. More precisely, the compression ratio achieved by LZ78 (resp. lzma command line tool has a similar interface to gzip (1) and bzip2 (1) and is intended to make. This algorithm is pretty fast and efficient but consumes high amounts of RAM. seiko spring drive. Lossless compression is generally used for so-called "discrete" data, such as database records, spreadsheets, word-processing files, and even some kinds of image and video information. It is used in popular compression. In addition, we propose a technique to dynamically change the degree of parallelism of the. Hardware accelerators are being considered as important architectural components in the context of datacenter customization to achieve high performance and low power. To use the LZ77 compression algorithm: Set the coding position to the beginning of the input stream. iphone wifi password sharing not working. LZ77 can be used for any data type. Solve the following exercises. Integrity checks performed with the CRC-32 or the ADLER 32 checksums. The process of compression can be divided in 3 steps:Find the longest match of a string that starts at the current. The VERIFYING THE CORRECTNESS OF A DEFLATE COMPRESSION ACCELERATOR patent was. The second field represents the number of bytes to copy from the already decoded output buffer (with 0. This mode is the default, and is mostly equivalent to zlib/gzip default compression level. How LZ77 Data Compression Works. In this post we are going to explore LZ77, a lossless data-compression algorithm created by Lempel and Ziv in 1977. Compress (data, configs?): Description: Compresses a string using the zlib format Input:. LZ77 and LZ78 are the two _____ algorithms published in papers by Abraham Lempel and Jacob Ziv in 1977 and 1978 (A) Lossy data compression (B) Lossless data compression (C) Both (D) None of the above Answer Correct option is B. A Python LZ77-Compressor. In-memory operations use the Zlib compressed data format (RFC 1950). Learn more about huffman code, image compression. Though this, like zopfli. The compressed block consists of one or more instructions. It is natural to compare the speed of LZ77 compression with block sorting compression [5],[14] because both schemes can be implemented by using suffix sorting. 19 7A. Compression ratio Binary representation For the binary representation, the commonly used values are:. In this post we are going to explore LZ77, a lossless data-compression algorithm created by Lempel and Ziv in 1977. LZ4HC is a "high-compression" variant of LZ4 that, I believe, changes point 1 above--the compressor finds more than one match between current and past data and looks for the best match to ensure the output is small. and compression ratio. Abstract: In a multimedia system, one is required to handle, store and transmit a lot of data. The two compression methods available are LZ77 and JPEG. The block sort-ing compression became famous now for the reason of a good balance of compression speed and ratio. 5 bits per character, however the entropy of English text . - Finally, about the "shorter hash chains", are you aware about the paper "Improving the Speed of LZ77 Compression by Hashing and Suffix Sorting" from Sadakane and Imai?. 32 2. A file to be compressed. pipelined FPGA accelerator that performs LZ77 compression and static Huffman encoding at rates up to 5. Compression algorithm details While it is the intent of this document to define the "deflate" compressed data format without reference to any particular compression algorithm, the format is related to the compressed formats produced by LZ77 (Lempel-Ziv 1977, see reference below); since many variations of LZ77 are patented, it is strongly. DEFLATE uses two Huffman tables. In Section 3 we show how the practical implementation of some LZ77 variants have abandoned the greedy parsing in order to increase the compression ratio and . Combined with its poor compression ratio (LZ77 is often superior) it is an unfeasible variant. . cones of calibration resin, for sale craiglist, used vibratory cable plow for sale, ralthy wireless controller manual, boobies porn, mature analvids, doggystylepull hair, ocd and regret reddit, service transmission shut off engine to engage park ram 1500, merced craigslist pets, used class b motorhomes for sale by owner, percy jackson fanfiction cerberus lemon co8rr