NAME

allpairs_multicore - executes All-Pairs workflow in parallel on a multicore machine

SYNOPSIS

allparis_multicore [options] <set A> <set B> <compare function>

DESCRIPTION

allpairs_multicore computes the Cartesian product of two sets (<set A> and <set B>), generating a matrix where each cell M[i,j] contains the output of the function F (<compare function>) on objects A[i] (an item in <set A>) and B[j] (an item in <set B>). The resulting matrix is displayed on the standard output, one comparison result per line along with the associated X and Y indices.

For large sets of objects, allpairs_multicore will use as many cores as you have available, and will carefully manage virtual memory to exploit locality and avoid thrashing. Because of this, you should be prepared for the results to come back in any order. If you want to further exploit the parallelism of executing All-Pairs workflows on multiple (multicore) machines, please refer to the allpairs_master(1) utility.

OPTIONS

-b, --block-size=<items>

Block size: number of items to hold in memory at once. (default: 50% of RAM)

-c, --cores=<cores>

Number of cores to be used. (default: # of cores in machine)

-e, --extra-args=<args>

Extra arguments to pass to the comparison program.

-d, --debug=<flag>

Enable debugging for this subsystem.

-v, --version

Show program version.

-h, --help

Display this message.

EXIT STATUS

On success, returns zero. On failure, returns non-zero.

EXAMPLES

Let's suppose you have a whole lot of files that you want to compare all to each other, named a, b, c, and so on. Suppose that you also have a program named compareit that when invoked as compareit a b will compare files a and b and produce some output summarizing the difference between the two, like this:



 a b are 45 percent similar

To use the allpairs framework, create a file called set.list that lists each of your files, one per line:



 a


 b


 c


 ...

Then, invoke allpairs_multicore like this:



 % allpairs_multicore set.list set.list compareit

The framework will carry out all possible comparisons of the objects, and print the results one by one (note that the first two columns are X and Y indices in the resulting matrix):



 1	1	a a are 100 percent similar


 1	2	a b are 45 percent similar


 1	3	a c are 37 percent similar


 ...