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9594db0cf2
[Feature #19236]
When building a large hash, pre-allocating it with enough
capacity can save many re-hashes and significantly improve
performance.
```
/opt/rubies/3.3.0/bin/ruby --disable=gems -rrubygems -I./benchmark/lib ./benchmark/benchmark-driver/exe/benchmark-driver \
--executables="compare-ruby::../miniruby-master -I.ext/common --disable-gem" \
--executables="built-ruby::./miniruby --disable-gem" \
--output=markdown --output-compare -v $(find ./benchmark -maxdepth 1 -name 'hash_new' -o -name '*hash_new*.yml' -o -name '*hash_new*.rb' | sort)
compare-ruby: ruby 3.4.0dev (2024-03-25T11:48:11Z master f53209f023) +YJIT dev [arm64-darwin23]
last_commit=[ruby/irb] Cache RDoc::RI::Driver.new (https://github.com/ruby/irb/pull/911)
built-ruby: ruby 3.4.0dev (2024-03-25T15:29:40Z hash-new-rb 77652b08a2) +YJIT dev [arm64-darwin23]
warming up...
| |compare-ruby|built-ruby|
|:-------------------|-----------:|---------:|
|new | 7.614M| 5.976M|
| | 1.27x| -|
|new_with_capa_1k | 13.931k| 15.698k|
| | -| 1.13x|
|new_with_capa_100k | 124.746| 148.283|
| | -| 1.19x|
```
40 lines
1.6 KiB
Ruby
40 lines
1.6 KiB
Ruby
class Hash
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# call-seq:
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# Hash.new(default_value = nil) -> new_hash
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# Hash.new(default_value = nil, capacity: size) -> new_hash
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# Hash.new {|hash, key| ... } -> new_hash
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# Hash.new(capacity: size) {|hash, key| ... } -> new_hash
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#
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# Returns a new empty +Hash+ object.
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#
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# The initial default value and initial default proc for the new hash
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# depend on which form above was used. See {Default Values}[rdoc-ref:Hash@Default+Values].
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#
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# If neither an argument nor a block is given,
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# initializes both the default value and the default proc to <tt>nil</tt>:
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# h = Hash.new
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# h.default # => nil
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# h.default_proc # => nil
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#
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# If argument <tt>default_value</tt> is given but no block is given,
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# initializes the default value to the given <tt>default_value</tt>
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# and the default proc to <tt>nil</tt>:
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# h = Hash.new(false)
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# h.default # => false
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# h.default_proc # => nil
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#
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# If a block is given but no <tt>default_value</tt>, stores the block as the default proc
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# and sets the default value to <tt>nil</tt>:
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# h = Hash.new {|hash, key| "Default value for #{key}" }
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# h.default # => nil
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# h.default_proc.class # => Proc
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# h[:nosuch] # => "Default value for nosuch"
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#
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# If both a block and a <tt>default_value</tt> are given, raises an +ArgumentError+
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#
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# If the optional keyword argument +capacity+ is given, the hash will be allocated
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# with enough capacity to accomodate this many keys without having to be resized.
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def initialize(ifnone = (ifnone_unset = true), capacity: 0, &block)
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Primitive.rb_hash_init(capacity, ifnone_unset, ifnone, block)
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end
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end
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