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Name

qarray_create - allocate a runtime distributed array

Synopsis

#include <qthread/qarray.h>

qarray *
qarray_create (const size_t count, const size_t unit_size);

qarray *
qarray_create_tight (const size_t count, const size_t unit_size);

qarray *
qarray_create_configured (const size_t count, const size_t unit_size, const distribution_t d, const char tight, const int seg_pages);

Description

These functions initialize qarray distributed array objects. All three functions create an array containing at least count elements that are at least unit_size bytes long each. The qarray_create() function may round the element size up to the next-largest multiple of eight, but the qarray_create_tight() is guaranteed not to do that, so that elements are packed tightly in the array. The qarray_create_configured() function provides greater control over the array implementation, allowing the distribution pattern (d), and the length of the distributed array segments (seg_pages) to be specified. The seg_pages argument specifies the number of memory pages in a single segment; memory cannot be distributed in units smaller than a single page. If seg_pages is zero, a default value is chosen.

The possible values for d are:

FIXED_HASH
Distributes the memory across the available shepherds evenly, using a basic round-robin assignment mechanism based on the address of the initial page of each segment. Array segments cannot be relocated.
FIXED_FIELDS
Distributes the memory evenly across all shepherds, maintaining long contiguous sets of segments on each shepherd. Segment locations are defined by a simple math operation on the index, so array segments cannot be relocated.
ALL_LOCAL
Assigns the entire array to the local shepherd. Array segments cannot be relocated.
ALL_RAND
Assigns the entire array to a random shepherd. Array segments cannot be relocated.
ALL_LEAST
Assigns the entire array to the shepherd with the least qarray segments currently assigned to it. Array segments cannot be relocated.
DIST_STRIPES
Assigns array segments with a round-robin mechanism. Segment location is stored in the segment, so segments can be relocated, but finding a segment requires extra memory operations.
DIST_FIELDS
Assigns array segments evenly across all shepherds, attempting to maintain long contiguous sets of segments on each shepherd. Segment location is stored in the segment, so segments can be relocated, but finding a segment requires extra memory operations.
DIST_RAND
Assigns array segments randomly to shepherds. Segment location is stored in the segment, so segments can be relocated, but finding a segment requires extra memory operations.
DIST_LEAST
Assigns each array segment to whichever shepherd has the fewest array segments assigned to it at creation time. Segment location is stored in the segment, so segments can be relocated, but finding a segment requires extra memory operations.

See Also

qarray_destroy(3) , qarray_iter(3) , qarray_shepof(3) , qarray_elem(3)

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