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/*
call with
speed20 N
where N is the number of segments (N >= 1), default 1
compile with
gcc speed21.c -o speed21 -O2 -lwgdb -lpthread
creating a flat pointer list of 10 million records of 5 fields in
a 1 GB database:
store a pointer to the previous record to field 3 of each record,
thus first list elems are actually created last.
Store lstlen-i to field 1.
Additionally create a ctrl record with pointers to the middle of the list,
to be used for parallel multicore scanning of the list later.
Ctrl record fields:
0: type (unused)
1: ptr field (3 here)
2: start pointer
3: midpointer0
4: midpointer1
...
N: ptr to last record
N+1: NULL
Observe that we use standard C int 0 for the NULL pointer,
this is also what wg_encode_null(db,0) always gives.
*/
#include <whitedb/dbapi.h>
#include <stdlib.h>
#include <stdio.h>
#define DB_NAME "20"
int main(int argc, char **argv) {
void *db, *rec, *ctrlrec, *firstrec, *lastrec;
char *name=DB_NAME;
int i;
int lstlen=10000000; // total nr of elems in list
int ptrfld=3; // field where a pointer is stored
int segnr=1; // total number of segments
int midcount=0; // middle ptr count
int midlasti=0; // last i where midpoint stored
int midseglen; // mid segment length
wg_int tmp;
if (argc>=2) {
segnr=atoi(argv[1]);
}
printf("creating a list with %d segments \n",segnr);
midseglen=lstlen/segnr; // mid segment length
db = wg_attach_database(name, 1000000000);
if (!db) { printf("db creation failed \n"); exit(0); }
ctrlrec = wg_create_record(db, 1000); // this will contain info about the list
// build the list
firstrec=wg_create_raw_record(db, 5);
lastrec=firstrec;
// next ptr from the last record is an encoded NULL pointer
wg_set_new_field(db,firstrec,ptrfld,wg_encode_null(db,0));
wg_set_new_field(db,firstrec,1,wg_encode_int(db,lstlen));
for(i=1;i<lstlen;i++) {
rec = wg_create_raw_record(db, 5);
if (!rec) { printf("record creation failed \n"); exit(0); }
// store a pointer to the previously built record
wg_set_new_field(db,rec,ptrfld,wg_encode_record(db,lastrec));
wg_set_new_field(db,rec,1,wg_encode_int(db,lstlen-i));
lastrec=rec;
// check if the pointer should be stored as as a midptr
// observe the last segment may be slightly longer
// example: lstlen=11, midnr=1: midseglen=5, midpoint0=5, at i=10 11-10<5
// example: lstlen=10, midnr=2: midseglen=3, midpoint0=3, midpoint1=6 at i=9 10-9<3
if (i-midlasti==midseglen && lstlen-i>=midseglen) {
// this lst is built from end to beginning
wg_set_field(db,ctrlrec,2+(segnr-1)-midcount,wg_encode_record(db,rec));
printf("\nmidpoint %d at i %d to field %d val %d",midcount,i,2+(segnr-1)-midcount,
(int)(db,wg_get_field(db,ctrlrec,2+(segnr-1)-midcount)));
midlasti=i;
midcount++;
}
}
// set ctrlrec fields: type,ptr field,first pointer,midpointer1,midpointer2,...
wg_set_field(db,ctrlrec,0,wg_encode_int(db,1)); // type not used
wg_set_field(db,ctrlrec,1,wg_encode_int(db,ptrfld)); // ptrs at field 3
wg_set_field(db,ctrlrec,2,wg_encode_record(db,lastrec)); // lst starts here
wg_set_field(db,ctrlrec,2+segnr,wg_encode_record(db,firstrec)); // last record in a list
printf("\nfinal i %d\n", i);
printf("\nctrl rec ptr fld val %d \n",wg_decode_int(db,wg_get_field(db,ctrlrec,1)));
for(i=0;i<1000;i++) {
tmp=wg_get_field(db,ctrlrec,2+i);
if (!(int)tmp) break;
printf("ptr %d value %d content %d\n",i,(int)tmp,
wg_decode_int(db,wg_get_field(db,wg_decode_record(db,tmp),1)) );
}
wg_detach_database(db);
return 0;
}
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