class 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.
Public Instance Methods
Adds the given value.
# File lib/thread_safe/util/adder.rb, line 24 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
# File lib/thread_safe/util/adder.rb, line 38 def decrement add(-1) end
# File lib/thread_safe/util/adder.rb, line 34 def increment add(1) end
# File lib/thread_safe/util/adder.rb, line 57 def reset internal_reset(0) 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.
# File lib/thread_safe/util/adder.rb, line 47 def sum x = base if current_cells = cells current_cells.each do |cell| x += cell.value if cell end end x end