Tests of the extended Starry 2MASS database

We added points with random coordinates to the 2MASS database so that the total number of the points has reached 1 billion.

After having expanded the database this way, its density gradients changed insignificantly. Density of stars in some regions of Milky Way is, as before, 1000 times higher than density of stars in the most rarefied regions of the Starry Sky.

After that we have conducted a test similar to the Test of the real 2MASS database.

Testable objects:
XY-coordinates of random points and Stars of the open database 2MASS, including added points.

1. Number of Stars (all Starry Sky with added points)

All sky

A density of Stars in some regions of the Milky Way can be 1000 times higher than a density of Stars in the most rarefied region of Starry Sky.
2. Size of the table of coordinates of Stars on hard disk

7.5 GB
3. Size of the index of coordinates of Stars

5.7 MB
4. The size of index related to the size of indexed coordinates of Stars (index was compressed to a half of its initial size) 0.07 %
5. Time of indexing coordinates of Stars 37 minutes
6. The size of RAM used by the shell program

4.6 MB
7. The size of RAM buffers allocated to organize range queries 0.1 MB
8. The size of the total RAM allocated during queries is insignificant: the size of the shell program (4.6 MB) + the size of the unpacked index (10.5 MB) + the size of buffer (0.1 MB).

The entire database remains on the hard disk, RAM is free.

4.6 + 10.5 + 0.1 = 15.2 MB
9. A speed of performance of range queries is very high. See video A tour to the extended 2MASS database. The video contains counters. real time

10. For comparison (on test computer):
Time of copying a 1.0 GB file to the same directory
1 min
11. For comparison (on test computer):
Time of compression a 1.0 GB file to format *.rar format
5 min 15 sec
12. For comparison (on test computer):
Time of compression a 1.0 GB file to format *.zip format
4 min 31 sec

Computer used in tests is a standard home desktop computer bought for $ 1000: Intel(R) Pentium(R) Dual CPU E2200 @ 2.20 GHz, 2.99 GB RAM.

Prior to generating the data, indexing and testing, there has been no preparation of the computer done nor has there been any disk defragmentation software used, i.e. the station was used in the current status "as is".

During test queries a disk space of the station was used up by 95 % (full size of disk space is 390 GB).

Platform: Microsoft Windows XP Professional, version 2002, Service Pack 2.

During the tests the computer was connected to the Internet, anti-virus system was active.

When saving the source base on a portable hard disk Seagate FreeAgent, the system works via USB-channel at approximately the same speed. Search time is the same as in case when the database is located on the hard disk.

Search Technology developed with support from FASIE
foundation formed by the Government of Russian Federation
Novosib-BIT LLC 2004 - 2017