coding_benchmark 0.1.5

The program for benchmarking Huffman coding algorithms
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use std::collections::HashMap;
use std::hint::black_box;

use bitm::{BitAccess, BitVec};
use butils::UnitPrefix;
use dyn_size_of::GetSize;
use minimum_redundancy::{BitsPerFragment, Code, Coding};
use minimum_redundancy::Frequencies;

use crate::compare_texts;

/// Prints speed of and returns counting symbol occurrences.
pub fn frequencies_u8(conf: &super::Conf, text: &[u8]) -> [usize; 256] {
    if conf.extra_test {
        conf.print_speed(" Counting symbol occurrences with array (u8 specific method)", conf.measure(||
            <[usize; 256]>::with_occurrences_of(text.iter())
        ));
    }
    let result = <[usize; 256]>::with_occurrences_of(text.iter());
    println!(" Input of length {} consists of {} different symbols, its entropy is {:.2} bits/symbol.",
        text.len(), result.number_of_occurring_values(), result.entropy());
    result
}

/// Prints speed of and returns counting symbol occurrences.
pub fn frequencies(conf: &super::Conf, text: &[u8]) -> HashMap::<u8, usize> {
    if conf.extra_test {
        conf.print_speed(" Counting symbol occurrences with HashMap (generic method)", conf.measure(||
            HashMap::<u8, usize>::with_occurrences_of(text.iter())
        ));
    }
    let result = HashMap::<u8, usize>::with_occurrences_of(text.iter());
    println!(" Input of length {} consists of {} different symbols, its entropy is {:.2} bits/symbol.",
        text.len(), result.number_of_occurring_values(), result.entropy());
    result
}

#[inline(always)] fn total_size_bits_u8(frequencies: &[usize; 256], book: &[minimum_redundancy::Code; 256]) -> usize {
    frequencies.frequencies().fold(0usize, |acc, (k, w)|
        acc + book[k as usize].len as usize * w
    )
}

#[inline(always)] fn compress_u8<'i>(text: impl IntoIterator<Item = &'i u8>, book: &[minimum_redundancy::Code; 256], compressed_size_bits: usize) -> Box<[u64]> {
    let mut compressed_text = Box::<[u64]>::with_zeroed_bits(compressed_size_bits);
    let mut bit_index = 0usize;
    for k in text {
        let c = book[*k as usize];
        compressed_text.init_bits(bit_index, c.content as u64, c.len.min(32) as u8);
        bit_index += c.len as usize;
    }
    assert_eq!(bit_index, compressed_size_bits);
    compressed_text
}

#[inline(always)] fn total_size_bits(frequencies: &HashMap<u8, usize>, book: &HashMap<u8, Code>) -> usize {
    frequencies.iter().fold(0usize, |acc, (k, w)|
        acc + book[&k].len as usize * *w
    )
}

#[inline(always)] fn compress<'i>(text: impl IntoIterator<Item = &'i u8>, book: &HashMap<u8, Code>, compressed_size_bits: usize) -> Box<[u64]> {
    let mut compressed_text = Box::<[u64]>::with_zeroed_bits(compressed_size_bits);
    let mut bit_index = 0usize;
    for k in text {
        let c = book[k];
        compressed_text.init_bits(bit_index, c.content as u64, c.len.min(32) as u8);
        bit_index += c.len as usize;
    }
    assert_eq!(bit_index, compressed_size_bits);
    compressed_text
}

#[inline(always)] fn decode(coding: &Coding<u8>, mut bits: impl Iterator<Item = bool>) {
    let mut d = coding.decoder();
    while let Some(b) = bits.next() {
        if let minimum_redundancy::DecodingResult::Value(v) = d.consume(b as u32) {
            black_box(v);
            d.reset();
        }
    }
}

#[inline(always)] fn decode_from_queue(coding: &Coding<u8>, compressed_text: &Box<[u64]>, total_size_bits: usize) {
    decode(coding, compressed_text.bit_in_range_iter(0..total_size_bits));
}

#[inline(always)] fn decode_from_stack(coding: &Coding<u8>, compressed_text: &Box<[u64]>, total_size_bits: usize) {
    decode(coding, compressed_text.bit_in_range_iter(0..total_size_bits).rev());
}

#[inline(always)] fn decoded(coding: &Coding<u8>, uncompressed_len: usize, mut bits: impl Iterator<Item = bool>) -> Vec::<u8> {
    let mut decoded_text = Vec::with_capacity(uncompressed_len);
    let mut d = coding.decoder();
    while let Some(b) = bits.next() {
        if let minimum_redundancy::DecodingResult::Value(v) = d.consume(b as u32) {
            decoded_text.push(*v);
            d.reset();
        }
    }
    decoded_text
}

fn verify_queue(text: &[u8], compressed_text: Box<[u64]>, coding: &Coding<u8>, total_size_bits: usize) {
    print!(" Verifying decoding from a queue... ");
    compare_texts(&text, &decoded(coding, compressed_text.len(),
        compressed_text.bit_in_range_iter(0..total_size_bits)));
}

fn verify_stack(text: &[u8], compressed_text: Box<[u64]>, coding: &Coding<u8>, total_size_bits: usize) {
    print!(" Verifying decoding from a stack... ");
    compare_texts(&text, &decoded(coding, compressed_text.len(),
        compressed_text.bit_in_range_iter(0..total_size_bits).rev()));
}

pub fn benchmark_u8(conf: &super::Conf) {
    //println!("Measuring the performance of u8-specific minimum_redundancy version:");
    println!("### minimum_redundancy with u8-specific optimizations ###");

    let text = conf.text();
    let frequencies = frequencies_u8(conf, &text);

    let dec_constr_ns = conf.measure(|| Coding::from_frequencies_cloned(BitsPerFragment(1), &frequencies)).as_nanos();
    let coding = Coding::from_frequencies_cloned(BitsPerFragment(1), &frequencies);
    let enc_constr_ns = conf.measure(|| coding.codes_for_values_array()).as_nanos();
    let rev_enc_constr_ns = conf.measure(|| coding.reversed_codes_for_values_array()).as_nanos();

    println!(" Decoder + suffix (prefix) encoder construction time [ns]: {:.0} + {:.0} ({:.0}) = {:.0} ({:.0})",
         dec_constr_ns, enc_constr_ns, rev_enc_constr_ns, dec_constr_ns+enc_constr_ns, dec_constr_ns+rev_enc_constr_ns);
    println!(" Decoder size: {} bytes", coding.size_bytes());

    println!(" Prefix order:");
    let book = coding.reversed_codes_for_values_array();
    conf.print_speed("  encoding without adding to bit vector", conf.measure(|| {
        for k in text.iter() { black_box(book[*k as usize]); }
    }));
    conf.print_speed("  encoding + adding to bit vector", conf.measure(|| {
        compress_u8(text.iter(), &book, total_size_bits_u8(&frequencies, &book))
    }));
    let compressed_size_bits = total_size_bits_u8(&frequencies, &book);
    let compressed_text = compress_u8(text.iter(), &book, compressed_size_bits);
    conf.print_compressed_size(compressed_size_bits);
    conf.print_speed("  decoding from a queue (without storing)",
     conf.measure(|| decode_from_queue(&coding, &compressed_text, compressed_size_bits)));
    if conf.verify { verify_queue(&text, compressed_text, &coding, compressed_size_bits); } else { drop(compressed_text); }

    println!(" Suffix order:");
    let book = coding.codes_for_values_array();
    conf.print_speed("  encoding without adding to bit vector", conf.measure(|| {
        for k in text.iter() { black_box(book[*k as usize]); }
    }));
    conf.print_speed("  encoding + adding to bit vector", conf.measure(|| {
        compress_u8(text.iter().rev(), &book, total_size_bits_u8(&frequencies, &book))
    }));
    let compressed_size_bits = total_size_bits_u8(&frequencies, &book);
    let compressed_text = compress_u8(text.iter().rev(), &book, compressed_size_bits);
    conf.print_compressed_size(compressed_size_bits);
    conf.print_speed("  decoding from a stack (without storing)",
    conf.measure(|| decode_from_stack(&coding, &compressed_text, compressed_size_bits)));
    if conf.verify { verify_stack(&text, compressed_text, &coding, compressed_size_bits); }
}

pub fn benchmark(conf: &super::Conf) {
    //println!("Measuring the performance of the generic minimum_redundancy version:");
    println!("### minimum_redundancy, generic version ###");
    
    let text = conf.text();
    let frequencies = frequencies(conf, &text);

    let dec_constr_ns = conf.measure(|| Coding::from_frequencies_cloned(BitsPerFragment(1), &frequencies)).as_nanos();
    let coding = Coding::from_frequencies_cloned(BitsPerFragment(1), &frequencies);
    let enc_constr_ns = conf.measure(|| coding.codes_for_values()).as_nanos();
    let rev_enc_constr_ns = conf.measure(|| coding.reversed_codes_for_values()).as_nanos();

    println!(" Decoder + suffix (prefix) encoder construction time [ns]: {:.0} + {:.0} ({:.0}) = {:.0} ({:.0})",
         dec_constr_ns, enc_constr_ns, rev_enc_constr_ns, dec_constr_ns+enc_constr_ns, dec_constr_ns+rev_enc_constr_ns);
    println!(" Decoder size: {} bytes", coding.size_bytes());
    println!(" Prefix order:");
    let book = coding.reversed_codes_for_values();
    conf.print_speed("  encoding without adding to bit vector", conf.measure(|| {
        for k in text.iter() { black_box(book.get(k)); }
    }));
    conf.print_speed("  encoding + adding to bit vector", conf.measure(|| {
        compress(text.iter(), &book, total_size_bits(&frequencies, &book))
    }));
    let compressed_size_bits = total_size_bits(&frequencies, &book);
    let compressed_text = compress(text.iter(), &book, compressed_size_bits);
    conf.print_compressed_size(compressed_size_bits);
    conf.print_speed("  decoding from a queue (without storing)",
     conf.measure(|| decode_from_queue(&coding, &compressed_text, compressed_size_bits)));
    if conf.verify { verify_queue(&text, compressed_text, &coding, compressed_size_bits); } else { drop(compressed_text); }

    println!(" Suffix order:");
    let book = coding.codes_for_values();
    conf.print_speed("  encoding without adding to bit vector", conf.measure(|| {
        for k in text.iter() { black_box(book.get(k)); }
    }));
    conf.print_speed("  encoding + adding to bit vector", conf.measure(|| {
        compress(text.iter().rev(), &book, total_size_bits(&frequencies, &book))
    }));
    let compressed_size_bits = total_size_bits(&frequencies, &book);
    let compressed_text = compress(text.iter().rev(), &book, compressed_size_bits);
    conf.print_compressed_size(compressed_size_bits);
    conf.print_speed("  decoding from a stack (without storing)",
    conf.measure(|| decode_from_stack(&coding, &compressed_text, compressed_size_bits)));
    if conf.verify { verify_stack(&text, compressed_text, &coding, compressed_size_bits); }
}