
265PEGASUS
is
blockblock elem elem elem
,, ,, ,
11 1
,, ,,rowcol mval
elem elem elem
. Similarly,
the format of a vector block with k nonzero elements is
id id vval
blockelemelem
,, ,,
11
(
. Only blocks with at least one nonzero elements are saved to disk.
This block encoding forces nearby edges in the adjacency matrix to be closely located;
it is different from Hadoop’ default behavior, which does not guarantee co-locating
them. After grouping, GIM-V is performed on blocks, not on individual elements.
GIM-V BL is illustrated in Figure 8.2.
In Section 8.5, we observe that GIM-V BL is at least 5 times faster ...