Struct mayda::unimodal::Unimodal
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pub struct Unimodal<B> { // some fields omitted }
The type of a unimodal encoded integer array. Designed for moderate
compression and efficient decoding through the Encodable
trait, and
efficient random access through the Access
trait.
Support is provided for arrays with as many as 237 entries, or 512 GiB of
u32
s. If your application requires more than that, you should probably
be designing your own data structure anyway.
Examples
use mayda::{Access, Encodable, Unimodal}; let input: Vec<u32> = vec![1, 4, 2, 8, 5, 7]; let mut bits = Unimodal::new(); bits.encode(&input).unwrap(); let output = bits.decode().unwrap(); assert_eq!(input, output); let value = bits.access(4); assert_eq!(value, 5); let range = bits.access(1..4); assert_eq!(range, vec![4, 2, 8]);
Performance
Decoding does not allocate except for the return value, and decodes around
6 GiB/s of decoded integers. Encoding allocates O(n)
memory (n
in the
length of the array), and encodes around 250 MiB/s of decoded integers.
Around three-fourths of the encoding runtime is due to the algorithm
utility::select_m
used to find the median of a block. Run
cargo bench --bench unimodal
for performance numbers on your setup.
The performance (speed and compression) degrades gradually as the number of entries falls below 128.
Safety
As a general rule, you should not decode or access Unimodal
objects
from untrusted sources.
A Unimodal
object performs unsafe pointer operations during encoding and
decoding. Changing the header information with mut_storage()
can cause
data to be written to or read from arbitrary addresses in memory.
Methods
impl<B: Bits> Unimodal<B>
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fn new() -> Self
Creates an empty Unimodal
object.
Examples
use mayda::{Encodable, Unimodal}; let input: Vec<u32> = vec![1, 4, 2, 8, 5, 7]; let mut bits = Unimodal::new(); bits.encode(&input).unwrap(); let bytes = std::mem::size_of_val(bits.storage()); assert_eq!(bytes, 16);
fn from_slice(slice: &[B]) -> Result<Self, Error>
Creates a Unimodal
object that encodes the slice.
Examples
use mayda::{Encodable, Unimodal}; let input: Vec<u32> = vec![1, 5, 7, 15, 20, 27]; let bits = Unimodal::from_slice(&input).unwrap(); let output = bits.decode().unwrap(); assert_eq!(input, output);
fn is_empty(&self) -> bool
Returns true when there are no encoded entries.
Examples
use mayda::Unimodal; let mut bits = Unimodal::<u32>::new(); assert_eq!(bits.is_empty(), true);
fn len(&self) -> usize
Returns the number of encoded entries.
Examples
use mayda::{Encodable, Unimodal}; let input: Vec<u32> = vec![1, 4, 2, 8, 5, 7]; let mut bits = Unimodal::new(); bits.encode(&input).unwrap(); assert_eq!(bits.len(), 6);
fn storage(&self) -> &[u32]
Exposes the word storage of the Unimodal
object.
Examples
use mayda::{Encodable, Unimodal}; let input: Vec<u32> = vec![1, 4, 2, 8, 5, 7]; let mut bits = Unimodal::new(); bits.encode(&input).unwrap(); let storage = bits.storage(); assert_eq!(storage.len(), 4);
unsafe fn mut_storage(&mut self) -> &mut Box<[u32]>
Exposes the mutable word storage of the Unimodal
object.
Safety
A Unimodal
object performs unsafe pointer operations during encoding and
decoding. Changing the header information can cause data to be written to
or read from arbitrary addresses in memory.
fn required_width(&self) -> u32
Returns the width of the encoded integer type.
Examples
use mayda::{Encodable, Unimodal}; let input: Vec<u32> = vec![1, 4, 2, 8, 5, 7]; let mut bits = Unimodal::new(); bits.encode(&input).unwrap(); assert_eq!(bits.required_width(), 32);
Trait Implementations
impl<B: PartialOrd> PartialOrd for Unimodal<B>
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fn partial_cmp(&self, __arg_0: &Unimodal<B>) -> Option<Ordering>
This method returns an ordering between self
and other
values if one exists. Read more
fn lt(&self, __arg_0: &Unimodal<B>) -> bool
This method tests less than (for self
and other
) and is used by the <
operator. Read more
fn le(&self, __arg_0: &Unimodal<B>) -> bool
This method tests less than or equal to (for self
and other
) and is used by the <=
operator. Read more
fn gt(&self, __arg_0: &Unimodal<B>) -> bool
This method tests greater than (for self
and other
) and is used by the >
operator. Read more
fn ge(&self, __arg_0: &Unimodal<B>) -> bool
This method tests greater than or equal to (for self
and other
) and is used by the >=
operator. Read more
impl<B: PartialEq> PartialEq for Unimodal<B>
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fn eq(&self, __arg_0: &Unimodal<B>) -> bool
This method tests for self
and other
values to be equal, and is used by ==
. Read more
fn ne(&self, __arg_0: &Unimodal<B>) -> bool
This method tests for !=
.
impl<B: Hash> Hash for Unimodal<B>
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fn hash<__HB: Hasher>(&self, __arg_0: &mut __HB)
Feeds this value into the state given, updating the hasher as necessary.
fn hash_slice<H>(data: &[Self], state: &mut H) where H: Hasher
1.3.0
Feeds a slice of this type into the state provided.
impl<B: Default> Default for Unimodal<B>
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impl<B: Debug> Debug for Unimodal<B>
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impl<B: Clone> Clone for Unimodal<B>
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fn clone(&self) -> Unimodal<B>
Returns a copy of the value. Read more
fn clone_from(&mut self, source: &Self)
1.0.0
Performs copy-assignment from source
. Read more
impl<B: Bits> Encodable<B> for Unimodal<B>
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fn encode(&mut self, input: &[B]) -> Result<(), Error>
Encodes the slice in the Encodable
object.
fn decode(&self) -> Result<Vec<B>, Error>
Decodes the slice in the Encodable
object. An encoded vector type must give ownership of the returned value to the caller. Read more
impl<B: Bits> Access<usize> for Unimodal<B>
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type Output = B
The type returned by the access operation.
fn access(&self, index: usize) -> B
The method for the access foo.access(bar)
operation.
impl<B: Bits> Access<Range<usize>> for Unimodal<B>
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type Output = Vec<B>
The type returned by the access operation.
fn access(&self, index: Range<usize>) -> Vec<B>
The method for the access foo.access(bar)
operation.
impl<B: Bits> Access<RangeFrom<usize>> for Unimodal<B>
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type Output = Vec<B>
The type returned by the access operation.
fn access(&self, index: RangeFrom<usize>) -> Vec<B>
The method for the access foo.access(bar)
operation.
impl<B: Bits> Access<RangeTo<usize>> for Unimodal<B>
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type Output = Vec<B>
The type returned by the access operation.
fn access(&self, range: RangeTo<usize>) -> Vec<B>
The method for the access foo.access(bar)
operation.
impl<B: Bits> Access<RangeFull> for Unimodal<B>
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type Output = Vec<B>
The type returned by the access operation.
fn access(&self, _: RangeFull) -> Vec<B>
The method for the access foo.access(bar)
operation.
impl<B: Bits> Access<RangeInclusive<usize>> for Unimodal<B>
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type Output = Vec<B>
The type returned by the access operation.
fn access(&self, range: RangeInclusive<usize>) -> Vec<B>
The method for the access foo.access(bar)
operation.