KMR Base Implementation (on-memory operations). More...

#include <mpi.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <limits.h>
#include <errno.h>
#include <assert.h>
#include <ctype.h>
#include "../config.h"
#include "kmr.h"
#include "kmrimpl.h"
#include "kmrtrace.h"

Macros
#define	BLOCK_SIZE (64 * 1024 * 1024)

#define	FIN()

#define	KEY(V)

#define	KMR_CMP3(X, Y) (((X) == (Y)) ? 0 : ((X) < (Y)) ? -1 : 1)

#define	MAP_PARK_SIZE (1024)

#define	MAX(a, b) (((a)>(b))?(a):(b))

#define	MIN(a, b) (((a)<(b))?(a):(b))

#define	MIX() (h ^= k, h = ROT(h, 31), h = h * 5 + 0xe6546b64)

#define	NEVERHERE 0

#define	PUSHOFF_SIZE (64 * 1024)

#define	ROT(X, N) ((X) << (N) \| (X) >> (64-(N)))

Functions
int	kmr_add_identity_fn (const struct kmr_kv_box kv, const KMR_KVS kvi, KMR_KVS kvo, void *arg, const long i)
	Adds a given key-value pair unmodified. More...

int	kmr_add_kv (KMR_KVS *kvs, const struct kmr_kv_box kv)
	Adds a key-value pair. More...

int	kmr_add_kv1 (KMR_KVS kvs, void k, int klen, void *v, int vlen)
	Adds a key-value pair as given directly by a pointer. More...

int	kmr_add_kv_done (KMR_KVS *kvs)
	Marks finished adding key-value pairs. More...

static int	kmr_add_kv_nomutex (KMR_KVS kvs, const struct kmr_kv_box kv, struct kmr_kv_box xkv, _Bool reserve_space_only)

int	kmr_add_kv_quick_ (KMR_KVS *kvs, const struct kmr_kv_box kv)

int	kmr_add_kv_space (KMR_KVS kvs, const struct kmr_kv_box kv, void keyp, void *valuep)
	Adds a key-value pair, but only allocates a space and returns the pointers to the key and the value parts. More...

int	kmr_add_string (KMR_KVS kvs, const char k, const char *v)
	Adds a key-value pair of strings. More...

int	kmr_allocate_block (KMR_KVS *kvs, size_t size)

static void	kmr_assert_on_tail_marker (KMR_KVS *kvs)

static kmr_record_sorter_t	kmr_choose_record_sorter (const KMR_KVS *kvs)

kmr_sorter_t	kmr_choose_sorter (const KMR_KVS *kvs)

static int	kmr_collapse_as_opaque (KMR_KVS kvi, KMR_KVS kvo, _Bool inspectp)

static int	kmr_compare_float8 (const struct kmr_kv_box p0, const struct kmr_kv_box p1)

static int	kmr_compare_integer (const struct kmr_kv_box p0, const struct kmr_kv_box p1)

static int	kmr_compare_lexicographically (const unsigned char p, const int plen, const unsigned char q, const int qlen)

static int	kmr_compare_opaque (const struct kmr_kv_box p, const struct kmr_kv_box q)

static int	kmr_compare_record_float8_ (const struct kmr_keyed_record p0, const struct kmr_keyed_record p1)

static int	kmr_compare_record_integer_ (const struct kmr_keyed_record p0, const struct kmr_keyed_record p1)

static int	kmr_compare_record_opaque (const struct kmr_keyed_record p0, const struct kmr_keyed_record p1)

int	kmr_concatenate_kvs (KMR_KVS kvs[], int nkvs, KMR_KVS kvo, struct kmr_option opt)
	Concatenates a number of KVSes to one. More...

static int	kmr_copy_record_fn (const struct kmr_kv_box kv, const KMR_KVS kvi, KMR_KVS kvo, void *p, const long i)

static long	kmr_count_entries (KMR_KVS *kvs, _Bool bound_in_block)

KMR *	kmr_create_context (const MPI_Comm comm, const MPI_Info conf, const char *identifying_name)
	Makes a new KMR context (a context has type KMR). More...

KMR *	kmr_create_context_world ()

KMR_KVS *	kmr_create_kvs7 (KMR mr, enum kmr_kv_field kf, enum kmr_kv_field vf, struct kmr_option opt, const char file, const int line, const char *func)
	Makes a new key-value stream with the specified field data-types. More...

static KMR_KVS *	kmr_create_raw_kvs (KMR mr, const KMR_KVS _similar)
	Makes a new key-value stream (type KMR_KVS). More...

int	kmr_fin (void)
	Clears the environment. More...

struct kmr_kvs_entry *	kmr_find_kvs_last_entry (KMR_KVS *kvs)
	Finds the last entry of a key-value stream. More...

int	kmr_free_context (KMR *mr)
	Releases a context created with kmr_create_context(). More...

int	kmr_free_kvs (KMR_KVS *kvs)
	Releases a key-value stream (type KMR_KVS). More...

static int	kmr_free_kvs_oncore (KMR_KVS *kvs)

KMR *	kmr_get_context_of_kvs (KMR_KVS const *kvs)

static signed long	kmr_hash_key (const KMR_KVS *kvs, const struct kmr_kv_box kv)

static unsigned long	kmr_hash_key_opaque (const unsigned char *p, int n)

static int	kmr_icmp (const void a0, const void a1)
	Compares the key field of keyed-records for qsort/bsearch. More...

int	kmr_init_2 (int ignore)

void	kmr_init_kvs_oncore (KMR_KVS kvs, KMR mr)

static void	kmr_kvs_adjust_adding_point (KMR_KVS *kvs)

int	kmr_legal_minimum_field_size (KMR *mr, enum kmr_kv_field f)
	Returns a minimum byte size of the field: 8 for INTEGER and FLOAT8, 0 for others. More...

int	kmr_map9 (_Bool stop_when_some_added, KMR_KVS kvi, KMR_KVS kvo, void arg, struct kmr_option opt, kmr_mapfn_t m, const char file, const int line, const char *func)
	Maps simply. More...

int	kmr_map_on_rank_zero (KMR_KVS kvo, void arg, struct kmr_option opt, kmr_mapfn_t m)
	Maps on rank0 only. More...

int	kmr_map_once (KMR_KVS kvo, void arg, struct kmr_option opt, _Bool rank_zero_only, kmr_mapfn_t m)
	Maps once. More...

static int	kmr_map_parked (struct kmr_kv_box ev, long evcnt, long mapcount, _Bool k_reclaim, _Bool v_reclaim, KMR_KVS kvi, KMR_KVS kvo, kmr_mapfn_t m, void arg, struct kmr_option opt)

int	kmr_map_rank_by_rank (KMR_KVS kvi, KMR_KVS kvo, void *arg, struct kmr_option opt, kmr_mapfn_t m)
	Maps sequentially with rank by rank for debugging. More...

int	kmr_map_skipping (long from, long stride, long limit, _Bool stop_when_some_added, KMR_KVS kvi, KMR_KVS kvo, void *arg, struct kmr_option opt, kmr_mapfn_t m)
	Maps by skipping the number of entries. More...

int	kmr_move_kvs (KMR_KVS kvi, KMR_KVS kvo, struct kmr_option opt)
	Moves the contents of the input KVI to the output KVO. More...

int	kmr_pitch_rank (const struct kmr_kv_box kv, KMR_KVS *kvs)

int	kmr_reduce9 (_Bool stop_when_some_added, KMR_KVS kvi, KMR_KVS kvo, void arg, struct kmr_option opt, kmr_redfn_t r, const char file, const int line, const char *func)
	Reduces key-value pairs. More...

int	kmr_reduce_as_one (KMR_KVS kvi, KMR_KVS kvo, void *arg, struct kmr_option opt, kmr_redfn_t r)
	Calls a reduce-function once as if all key-value pairs had the same key. More...

static int	kmr_reduce_nothreading (KMR_KVS kvi, KMR_KVS kvo, void *arg, struct kmr_option opt, kmr_redfn_t r)

static int	kmr_reduce_threading (_Bool stop_when_some_added, KMR_KVS kvi, KMR_KVS kvo, void *arg, struct kmr_option opt, kmr_redfn_t r)

int	kmr_replicate (KMR_KVS kvi, KMR_KVS kvo, struct kmr_option opt)
	Replicates key-value pairs to be visible on all ranks, that is, it has the effect of bcast or all-gather. More...

int	kmr_restore_kvs (KMR_KVS kvo, void data, size_t sz_, struct kmr_option opt)
	Unpacks locally the contents of a key-value stream from a byte array. More...

int	kmr_retrieve_keyed_records (KMR_KVS kvs, struct kmr_keyed_record ev, long n, _Bool shuffling, _Bool ranking)
	Fills keyed records in an array for sorting. More...

int	kmr_retrieve_kvs_entries (KMR_KVS kvs, struct kmr_kvs_entry *ev, long n)
	Fills local key-value entries in an array for inspection. More...

int	kmr_save_kvs (KMR_KVS kvs, void dataq, size_t szq, struct kmr_option opt)
	Packs locally the contents of a key-value stream to a byte array. More...

int	kmr_scan_locally (KMR_KVS kvi, KMR_KVS carryin, KMR_KVS kvo, KMR_KVS carryout, kmr_redfn_t r)
	Scans every key-value with a reduce-function locally (independently on each rank). More...

int	kmr_shuffle (KMR_KVS kvi, KMR_KVS kvo, struct kmr_option opt)
	Shuffles key-value pairs to the appropriate destination ranks. More...

int	kmr_sort_locally (KMR_KVS kvi, KMR_KVS kvo, _Bool shuffling, struct kmr_option opt)
	Reorders key-value pairs in a single rank. More...

static int	kmr_sort_locally_lo (KMR_KVS kvi, KMR_KVS kvo, _Bool shuffling, _Bool ranking, struct kmr_option opt)

signed long	kmr_stable_key (const struct kmr_kv_box kv, const KMR_KVS *kvs)

static long	kmr_stable_key_opaque (const struct kmr_kv_box kv)

int	kmr_take_one (KMR_KVS kvi, struct kmr_kv_box kv)
	Extracts a single key-value pair locally in the key-value stream KVI. More...

static void	kmr_unlink_kvs (KMR_KVS *kvs)

Variables
int	KMR_API_ID = 0

const int	kmr_version = KMR_H

Detailed Description

KMR Base Implementation (on-memory operations).

KMR aims at fast shuffling and scalability, and provides modest utilities for programming with map-reduce. This part implements on-memory operations.

Definition in file kmrbase.c.

Macro Definition Documentation

#define KEY ( V )

Value:

(k = (V), k *= 0x87c37b91114253d5UL, \

k = ROT(k, 31), k *= 0x4cf5ad432745937fUL)

#define FIN ( )

Value:

(h ^= (h >> 33), h *= 0xff51afd7ed558ccdUL, h ^= (h >> 33), \

h *= 0xc4ceb9fe1a85ec53UL, h ^= (h >> 33))

Function Documentation

int kmr_fin ( void )

Clears the environment.

Definition at line 124 of file kmrbase.c.

KMR* kmr_create_context	(	const MPI_Comm	comm,
		const MPI_Info	conf,
		const char *	identifying_name
	)

Makes a new KMR context (a context has type KMR).

A KMR context is a record of common information to all key-value streams. COMM is a communicator for use inside. It dups the given communicator inside, to avoid conflicts with other calls to MPI functions. MPI should be initialized with a thread support level of either MPI_THREAD_SERIALIZED or MPI_THREAD_MULTIPLE. CONF specifies configuration options. It should be freed after a call. The options can differ on each rank, (in this version). The configuration options are first taken from a file with a name specified by the environment variable "KMROPTION" on rank0, and they are merged with the explicitly given ones. The KMROPTION file has the file format of Java properties (but only in Latin characters). Refer to JDK documents on "java.util.Properties" (on "load" method) for the file format. The explicitly given ones have precedence. IDENTIFYING_NAME is just recorded in the context, and has no specific use. It may be null.

Definition at line 147 of file kmrbase.c.

int kmr_free_context ( KMR * mr )

Releases a context created with kmr_create_context().

Definition at line 326 of file kmrbase.c.

static KMR_KVS* kmr_create_raw_kvs	(	KMR *	mr,
		const KMR_KVS *	_similar
	)

static

Makes a new key-value stream (type KMR_KVS).

It allocates by the size of the union, which may be larger than the necessary.

Definition at line 418 of file kmrbase.c.

KMR_KVS* kmr_create_kvs7	(	KMR *	mr,
		enum kmr_kv_field	kf,
		enum kmr_kv_field	vf,
		struct kmr_option	opt,
		const char *	file,
		const int	line,
		const char *	func
	)

Makes a new key-value stream with the specified field data-types.

Definition at line 510 of file kmrbase.c.

int kmr_move_kvs	(	KMR_KVS *	kvi,
		KMR_KVS *	kvo,
		struct kmr_option	opt
	)

Moves the contents of the input KVI to the output KVO.

It consumes the input KVI. Calling kmr_map() with a null map-function has the same effect. Effective-options: TAKE_CKPT. See struct kmr_option.

Definition at line 534 of file kmrbase.c.

int kmr_free_kvs ( KMR_KVS * kvs )

Releases a key-value stream (type KMR_KVS).

Normally, mapper/shuffler/reducer consumes and frees the input key-value stream, and explicit calls are unnecessary. Here, mapper/shuffler/reducer includes kmr_map(), kmr_map_on_rank_zero(), kmr_map_ms(), kmr_shuffle(), kmr_replicate(), kmr_reduce(), and kmr_reduce_as_one().

Definition at line 621 of file kmrbase.c.

int kmr_add_kv	(	KMR_KVS *	kvs,
		const struct kmr_kv_box	kv
	)

Adds a key-value pair.

(It is with serialization when a map-function is threaded).

Definition at line 751 of file kmrbase.c.

int kmr_add_kv1	(	KMR_KVS *	kvs,
		void *	k,
		int	klen,
		void *	v,
		int	vlen
	)

Adds a key-value pair as given directly by a pointer.

An integer or a double be passed by a pointer (thus like &v).

Definition at line 779 of file kmrbase.c.

int kmr_add_kv_space	(	KMR_KVS *	kvs,
		const struct kmr_kv_box	kv,
		void **	keyp,
		void **	valuep
	)

Adds a key-value pair, but only allocates a space and returns the pointers to the key and the value parts.

It may enable to create a large key/value data directly in the space. It does not return a proper value if a key/value field is not a pointer. (It cannot be used with a "push-off" key-value stream, because its buffer will be sent out and late fill-in the buffer causes a race).

Definition at line 843 of file kmrbase.c.

int kmr_add_kv_done ( KMR_KVS * kvs )

Marks finished adding key-value pairs.

Further addition will be prohibited. Normally, mapper/shuffler/reducer finishes the output key-value stream by itself, and explicit calls are unnecessary. Here, mapper/shuffler/reducer includes kmr_map(), kmr_map_on_rank_zero(), kmr_map_ms(), kmr_shuffle(), kmr_replicate(), and kmr_reduce().

Definition at line 881 of file kmrbase.c.

int kmr_add_string	(	KMR_KVS *	kvs,
		const char *	k,
		const char *	v
	)

Adds a key-value pair of strings.

The key and value fields should be of opaque data.

Definition at line 913 of file kmrbase.c.

int kmr_add_identity_fn	(	const struct kmr_kv_box	kv,
		const KMR_KVS *	kvi,
		KMR_KVS *	kvo,
		void *	arg,
		const long	i
	)

Adds a given key-value pair unmodified.

It is a map-function.

Definition at line 937 of file kmrbase.c.

int kmr_save_kvs	(	KMR_KVS *	kvs,
		void **	dataq,
		size_t *	szq,
		struct kmr_option	opt
	)

Packs locally the contents of a key-value stream to a byte array.

It is used to save or to send a key-value stream. It returns the allocated memory with its size, and it should be freed by the user. It may fail on allocating a buffer, and then it returns MPI_ERR_BUFFER. Its reverse is performed by kmr_restore_kvs().

Definition at line 968 of file kmrbase.c.

int kmr_restore_kvs	(	KMR_KVS *	kvo,
		void *	data,
		size_t	sz_,
		struct kmr_option	opt
	)

Unpacks locally the contents of a key-value stream from a byte array.

It is a reverse of kmr_save_kvs().

Definition at line 1034 of file kmrbase.c.

int kmr_map_skipping	(	long	from,
		long	stride,
		long	limit,
		_Bool	stop_when_some_added,
		KMR_KVS *	kvi,
		KMR_KVS *	kvo,
		void *	arg,
		struct kmr_option	opt,
		kmr_mapfn_t	m
	)

Maps by skipping the number of entries.

It calls a map-function on entries from FROM, skipping by STRIDE, up to LIMIT non-inclusive. See kmr_map().

Definition at line 1134 of file kmrbase.c.

int kmr_map9	(	_Bool	stop_when_some_added,
		KMR_KVS *	kvi,
		KMR_KVS *	kvo,
		void *	arg,
		struct kmr_option	opt,
		kmr_mapfn_t	m,
		const char *	file,
		const int	line,
		const char *	func
	)

Maps simply.

It consumes the input key-value stream KVI unless INSPECT option is marked. The output key-value stream KVO can be null, but in that case, a map-function cannot add key-value pairs. The pointer ARG is just passed to a map-function as a general argument, where accesses to it should be race-free, since a map-function is called by threads by default. M is the map-function. See the description on the type kmr_mapfn_t. It copeis the contents of the input KVI to the output KVO, when a map-function is null. During processing, it first makes an array pointing to the key-value entries in each data block, and works on it for ease threading/parallelization. Effective-options: NOTHREADING, INSPECT, KEEP_OPEN, COLLAPSE, TAKE_CKPT. See struct kmr_option.

Definition at line 1289 of file kmrbase.c.

int kmr_map_rank_by_rank	(	KMR_KVS *	kvi,
		KMR_KVS *	kvo,
		void *	arg,
		struct kmr_option	opt,
		kmr_mapfn_t	m
	)

Maps sequentially with rank by rank for debugging.

See kmr_map.

Definition at line 1339 of file kmrbase.c.

int kmr_take_one	(	KMR_KVS *	kvi,
		struct kmr_kv_box *	kv
	)

Extracts a single key-value pair locally in the key-value stream KVI.

It is an error when zero or more than one entries are in the KVI. It does not consume the input KVS (INSPECT IMPLIED). The returned key-value entry must be used before freeing the input KVS, when it points to an opaque data.

Definition at line 1369 of file kmrbase.c.

int kmr_map_once	(	KMR_KVS *	kvo,
		void *	arg,
		struct kmr_option	opt,
		_Bool	rank_zero_only,
		kmr_mapfn_t	m
	)

Maps once.

It calls a map-function once with a dummy key-value stream and a dummy key-value pair. See kmr_map(). Effective-options: KEEP_OPEN, TAKE_CKPT. See struct kmr_option.

Definition at line 1402 of file kmrbase.c.

int kmr_map_on_rank_zero	(	KMR_KVS *	kvo,
		void *	arg,
		struct kmr_option	opt,
		kmr_mapfn_t	m
	)

Maps on rank0 only.

It calls a map-function once with a dummy key-value stream and a dummy key-value pair. It is used to avoid low-level conditionals like (myrank==0). See kmr_map(). Effective-options: KEEP_OPEN, TAKE_CKPT. See struct kmr_option.

Definition at line 1456 of file kmrbase.c.

static int kmr_icmp	(	const void *	a0,
		const void *	a1
	)

static

Compares the key field of keyed-records for qsort/bsearch.

Definition at line 1815 of file kmrbase.c.

int kmr_sort_locally	(	KMR_KVS *	kvi,
		KMR_KVS *	kvo,
		_Bool	shuffling,
		struct kmr_option	opt
	)

Reorders key-value pairs in a single rank.

It sorts pairs when SHUFFLING is false, or gathers pairs with the same hashed keys adjacent when SHUFFLING is true. It only respects for not ordering but just equality when shuffling. The sort-keys for shuffling are destination ranks for shuffling (taking a modulo of the hashed key with nprocs). As a sorting, it is NOT-STABLE due to quick-sort used inside. It converts pointer keys and values to opaque ones for sending.
Sorting on a key-value stream is by memcmp(), unless the keys are integer or floating-point numbers (ordering on integers and memcmp() are different). Sorting on non-numbers is performed in two steps: the first step sorts by the integer rankings, and the second by the specified comparator. And thus, the comparator is required to have a corresponding generator of integer rankings. It consumes the input key-value stream. Effective-options: NOTHREADING, INSPECT, KEY_AS_RANK.

Definition at line 1993 of file kmrbase.c.

int kmr_shuffle	(	KMR_KVS *	kvi,
		KMR_KVS *	kvo,
		struct kmr_option	opt
	)

Shuffles key-value pairs to the appropriate destination ranks.

It first sorts pairs by the destination ranks of the keys, and then exchanges pairs with all-to-all communication. It converts pointer keys and values to opaque ones for sending during the sorting stage. Note that the key-value pairs are sorted by the hash-values prior to exchange. Effective-options: INSPECT, KEY_AS_RANK, TAKE_CKPT. See struct kmr_option.

Definition at line 2036 of file kmrbase.c.

int kmr_replicate	(	KMR_KVS *	kvi,
		KMR_KVS *	kvo,
		struct kmr_option	opt
	)

Replicates key-value pairs to be visible on all ranks, that is, it has the effect of bcast or all-gather.

It gathers pairs on rank0 only by the option RANK_ZERO. It moves stably, keeping the ordering of ranks and the ordering of local key-value pairs. Effective-options: INSPECT, RANK_ZERO, TAKE_CKPT. See struct kmr_option.

Definition at line 2182 of file kmrbase.c.

int kmr_reduce9	(	_Bool	stop_when_some_added,
		KMR_KVS *	kvi,
		KMR_KVS *	kvo,
		void *	arg,
		struct kmr_option	opt,
		kmr_redfn_t	r,
		const char *	file,
		const int	line,
		const char *	func
	)

Reduces key-value pairs.

It does not include shuffling, and thus, it requires being preceded by shuffling. Or, it works on local data (as a local combiner), if it is not preceded by shuffling. It always consumes the input key-value stream KVI. An output key-value stream KVO can be null. It passes an array of key-value pairs to a reduce-function whose keys are all equal (equality is by bits). The pointer ARG is just passed to a reduce-function as a general argument, where accesses to it should be race-free, since a reduce-function is called by threads by default. R is a reduce-function. See the description on the type kmr_redfn_t. A reduce-function may see a different input key-value stream (internally created one) instead of the one given. During reduction, it first scans adjacent equal keys, then calls a given reduce-function. Effective-options: NOTHREADING, INSPECT, TAKE_CKPT. See struct kmr_option.

Definition at line 2549 of file kmrbase.c.

int kmr_reduce_as_one	(	KMR_KVS *	kvi,
		KMR_KVS *	kvo,
		void *	arg,
		struct kmr_option	opt,
		kmr_redfn_t	r
	)

Calls a reduce-function once as if all key-value pairs had the same key.

See kmr_reduce(). Effective-options: INSPECT, TAKE_CKPT. See struct kmr_option.

Definition at line 2625 of file kmrbase.c.

int kmr_concatenate_kvs	(	KMR_KVS *	kvs[],
		int	nkvs,
		KMR_KVS *	kvo,
		struct kmr_option	opt
	)

Concatenates a number of KVSes to one.

Inputs are consumed. (It is fast because the key-value data is stored internally as a list of data blocks, and this routine just links them). Note that concatenating KVS can in effect be performed by consecutive calls to kmr_map() with the KEEP_OPEN option using the same output KVS. Effective-options: none.

Definition at line 2696 of file kmrbase.c.

struct kmr_kvs_entry* kmr_find_kvs_last_entry ( KMR_KVS * kvs )

Finds the last entry of a key-value stream.

It returns null when a key-value stream is empty. It sequentially scans all the entries and slow.

Definition at line 2759 of file kmrbase.c.

int kmr_retrieve_kvs_entries	(	KMR_KVS *	kvs,
		struct kmr_kvs_entry **	ev,
		long	n
	)

Fills local key-value entries in an array for inspection.

The returned pointers point to the inside of the KVS. The array EV should be as large as N. It implies inspect.

Definition at line 2801 of file kmrbase.c.

int kmr_retrieve_keyed_records	(	KMR_KVS *	kvs,
		struct kmr_keyed_record *	ev,
		long	n,
		_Bool	shuffling,
		_Bool	ranking
	)

Fills keyed records in an array for sorting.

The array EV should be as large as N. It implies inspect.

Definition at line 2820 of file kmrbase.c.

int kmr_legal_minimum_field_size	(	KMR *	mr,
		enum kmr_kv_field	f
	)

Returns a minimum byte size of the field: 8 for INTEGER and FLOAT8, 0 for others.

Definition at line 2847 of file kmrbase.c.

int kmr_scan_locally	(	KMR_KVS *	kvi,
		KMR_KVS *	carryin,
		KMR_KVS *	kvo,
		KMR_KVS *	carryout,
		kmr_redfn_t	r
	)

Scans every key-value with a reduce-function locally (independently on each rank).

It works in the order in the KVS. It ignores differences of the keys. It gets the start value from CARRYIN and puts the final value to CARRYOUT. The output has the same number of entries as the input. The carry-in and carry-out have one entry. The carry-out can be null. The reduce-function is called on each key-value pair as the right operand with the previous value as the left operand, and it should output a single value. The key part of the output is ignored and a pair is stored under the original key.

Definition at line 2880 of file kmrbase.c.

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