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 21 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 35 def decrement add(-1) end
# File lib/thread_safe/util/adder.rb, line 31 def increment add(1) end
# File lib/thread_safe/util/adder.rb, line 54 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 44 def sum x = base if current_cells = cells current_cells.each do |cell| x += cell.value if cell end end x end