Map_function
modules must be created using the Make_map_function
or
Make_map_function_with_init
functors. The init variety allows you to specify an
init
function that takes a "param" argument. The non-init variety is equivalent to
the init variety with init
equal to return
and a unit
"param"
argument. Similarly, Map_reduce_function
modules must be created using the
Make_map_combine_function
or Make_map_combine_function_with_init
functors.
The map_unordered
operation takes 'a Pipe.Reader.t
along with a Map_function
and
sends the 'a
values to workers for mapping. Each pair in the resulting ('b * int)
Pipe.Reader.t
contains the mapped value and the index of the value in the input
pipe.
The map
operation is similar to map_unordered
, but the result is a 'b
Pipe.Reader.t
where the mapped values are guaranteed to be in the same order as the
input values.
The find_map
operation takes 'a Pipe.Reader.t
along with a Map_function
that
returns 'b option
values. As soon as map
returns Some value
, all workers are
stopped and Some value
is returned. If map
never returns Some value
then None
is returned. If more than one worker returns Some value
, one value is chosen
arbitrarily and returned.
functions
The map_reduce_commutative
operation takes 'a Pipe.Reader.t
along with a
Map_reduce_function
and applies the map
function to 'a
values (in an unspecified
order), resulting in 'accum
values. The combine
function is then called to combine
the 'accum
values (in an unspecified order) into a single 'accum
value. Commutative map-reduce assumes that combine
is associative and
commutative.
The map_reduce
operation makes strong guarantees about the order in which the values
are processed by combine
. For a list a_0, a_1, a_2, ..., a_n of 'a
values, the
noncommutative map-reduce operation applies the map
function to produce
acc_{i,i+1}
from each a_i
. The combine
function is used to compute combine
acc_{i,j} acc_{j,k}
for i<j<k, producing acc_{i,k}
. The map
and combine
functions are called repeatedly until the entire list is reduced to a single
acc_{0,n+1}
value. Noncommutative map-reduce assumes that combine
is
associative.