class Concurrent::ThreadSafe::Util::Adder
A Ruby port of the Doug Lea’s jsr166e.LondAdder class version 1.8 available in public domain.
Original source code available here: gee.cs.oswego.edu/cgi-bin/viewcvs.cgi/jsr166/src/jsr166e/LongAdder.java?revision=1.8
One or more variables that together maintain an initially zero sum. When updates (method add
) are contended across threads, the set of variables may grow dynamically to reduce contention. Method sum
returns the current total combined across the variables maintaining the sum.
This class is usually preferable to single Atomic
reference when multiple threads update a common sum that is used for purposes such as collecting statistics, not for fine-grained synchronization control. Under low update contention, the two classes have similar characteristics. But under high contention, expected throughput of this class is significantly higher, at the expense of higher space consumption.
@!visibility private
Public Instance Methods
Source
# File lib/concurrent-ruby/concurrent/thread_safe/util/adder.rb, line 35 def add(x) if (current_cells = cells) || !cas_base_computed {|current_base| current_base + x} was_uncontended = true hash = hash_code unless current_cells && (cell = current_cells.volatile_get_by_hash(hash)) && (was_uncontended = cell.cas_computed {|current_value| current_value + x}) retry_update(x, hash, was_uncontended) {|current_value| current_value + x} end end end
Adds the given value.
Source
# File lib/concurrent-ruby/concurrent/thread_safe/util/adder.rb, line 49 def decrement add(-1) end
Source
# File lib/concurrent-ruby/concurrent/thread_safe/util/adder.rb, line 45 def increment add(1) end
Source
# File lib/concurrent-ruby/concurrent/thread_safe/util/adder.rb, line 68 def reset internal_reset(0) end
Source
# File lib/concurrent-ruby/concurrent/thread_safe/util/adder.rb, line 58 def sum x = base if current_cells = cells current_cells.each do |cell| x += cell.value if cell end end x end
Returns the current sum. The returned value is NOT an atomic snapshot: Invocation in the absence of concurrent updates returns an accurate result, but concurrent updates that occur while the sum is being calculated might not be incorporated.