Question

I have 2 database files and among those one I had to search for which I used 4 methods namely: in-memory sequential, in-memory binary, disk sequential and disk binary. The file which needed to be searched was 20Kb in size. The expected running time for these 4 programs should have been

disk sequential > disk binary > in-memory sequential > in-memory binary but its coming out to be
disk binary > disk sequential > in-memory sequential > in-memory binary.

Disk binary is taking around 1.5 sec more than the disk sequential. Why so?
I have calculated the time as printing the time before opening the file and then after opening the file and doing the search.

Thanks!

Answer 1

It can depends on the small size of your file; disk is not like main memory, it’s divided in blocks and your file won’t be probably bigger than 20 blocks.
So log_2(20) is about 5 and then binary search won’t be better unless what you’re searching for is after the fifth block.