I’ve changed the app to populate v with the query result and noted the free ram
before and after each resize. I’m hoping that addresses some of the concerns re
compiler optimisations even if it doesn’t supply any real answers? Results were
similar to before.
#include <vcl.h>
#include <windows.h>
#pragma hdrstop
#pragma argsused
#include <tchar.h>
#include <stdio.h>
#include <conio.h>
#include <iostream>
#include <vector>
#include "sqlite.h"
std::vector<int64_t> v;
const int Size[]={112000000,1000000000}; // 112 million, 1 billion
uint64_t FreeMBs()
{
MEMORYSTATUSEX status;
status.dwLength = sizeof(status);
GlobalMemoryStatusEx(&status);
return status.ullAvailPhys / (1024 * 1024);
}
int _tmain(int argc, _TCHAR* argv[])
{
sqlite3 *DB;
sqlite3_open("c:/SQLiteData/MyTemp.db",&DB);
sqlite3_stmt *stmt;
sqlite3_prepare_v2(DB,"select RowID from Big order by
RowID",-1,&stmt,NULL);
std::cout << FreeMBs() << " MB" << std::endl;
for (int i=0; i<2; i++)
{
v.resize(Size[i]);
v.shrink_to_fit();
int64_t Memi=FreeMBs();
clock_t Start=clock();
for (int i=0; i<Size[0] && sqlite3_step(stmt)==SQLITE_ROW; i++)
v[i]=sqlite3_column_int64(stmt,0);
std::cout << 1.0*(clock()-Start)/CLOCKS_PER_SEC << " secs -
Mem" << i << " = "
<< Memi << " MB" << std::endl;
sqlite3_reset(stmt);
}
sqlite3_finalize(stmt);
sqlite3_close(DB);
getch();
return 0;
}
OUTPUT (5 runs)
12891 MB
21.234 secs - Mem0 = 12042 MB
26.828 secs - Mem1 = 5290 MB
12951 MB
22.344 secs - Mem0 = 12092 MB
27.063 secs - Mem1 = 5332 MB
12658 MB
22.938 secs - Mem0 = 11803 MB
27.047 secs - Mem1 = 5071 MB
12820 MB
22.734 secs - Mem0 = 11970 MB
26.688 secs - Mem1 = 5211 MB
12803 MB
22.469 secs - Mem0 = 11954 MB
26.609 secs - Mem1 = 5209 MB
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