# A New Lossless DNA Compression Algorithm Based on A Single-Block Encoding Scheme
###### Abstract
A novel attempt with the multiple dictionaries based on Lempel-Ziv-Welch (LZW) and binary search has been presented in [47]. The performance of this algorithm is tested using a non-real DNA dataset. To overcome the limitation of the Huffbit algorithm [40]. A Modified Huffbit compression algorithm was introduced in 2018 [48]. It encodes the bases according to their frequency, which means that the base that occurs more often will be encoded with the shortest code. Recently, a cloud-based symbol table driven DNA compression algorithm (CBSTD) using R language was proposed in [6]. In this technique, the entire DNA sequence is subdivided into blocks (each block contains four bases), and then looked into which category it belongs. According to the occurrences of the nucleotide bases, three different categories are suggested. The first situation is when all four symbols are different, and hence, a table of 24 symbols is created to encode each block. The second situation is when the two nonconsecutive symbols are the same; then the block is divided into two parts and encoded using another table of symbols. The third situation is when two or more consecutive symbols are the same, in which case it is encoded with the bases followed by the number of occurrences. The authors in [6; 40; 48] do not use the real biological sequences to test the performance of their algorithms. In [49], the authors illustrate an efficient genome compression method based on the optimization of the context weighting, abbreviated as OPGC. The authors in [50] introduced the OBComp, which is based on the frequencies of bases including other symbols than ACGT. Only a single bit is required to encode the two nucleotide bases that occur most frequently, and the positions of the two other bases will be recorded separately before removing them from the original file. The first output will be encoded using modified run length encoding [51] and Huffman coding [40], whereas the position files are transformed using data differencing, which can improve the final compression. One of the general compressors based on asymmetric binary coding is used to generate the final compressed data. Generally, compression algorithms that look for approximate or even exact repeats have a high execution time overhead, as well as a high storage complexity, which is not suitable for an efficient compression technique. The following described methods are reference-free methods that have been designed for compressing files in FASTA and FASTQ formats. Three of the selected tools compress FASTA files only. The first one is called BIND [52]. It is a lossless FASTA/multi FASTA compressor specialized for compressing nucleotide sequence data. After the separation of the head(s), 7-Zip is used to compress them; non-ATGC characters and lowercase character is also removed from the original data and their positions are stored separately. Each nucleotide (A, T, G and C) is represented with an individual binary code (00, 01, 10 and 11) and then splits the codes into two data streams. After that, the repeat patterns in these two data streams are encoded using a unary coding scheme. Finally, BIND uses the LZM algorithm to compress the output files. The DELIMINATE [7] is an efficient lossless FASTA/multi FASTA compressor, it separately handles the header and sequence and it performs the compression in two phases. Firstly, all lower-case characters, as well as all non-ATGC, are recorded and eliminated from the original file. Secondly, the positions of the two most repeated nucleotide bases are transformed using delta encoding; then, the two other bases are encoded by binary encoding. Finally, all generated data output files are archived using 7-Zip. The MFCompress [8] is one of the most efficient lossless non-referential compression algorithms for FASTA files compaction according to a recent survey [13]. It divides the data into two separate kinds of data: one containing the nucleotide sequences, the other one the headers of the FASTA records.