Here we go!

n-way-merge.c

On my old home computer it merges at around 3GB/min, 100GB in half an hour.

As it is just a prove of concept, it can only handle records formed by integers of type int64_t.

The meaning of the constants are as follows: 

N = maximum number of files that can be sorted
CHUNKSIZE = the per-file memory buffer
KEYSIZE = the number of int64_t numbers per record

[download]
The source files are passed as arguments on the command line, the sorted output is sent to STDOUT. Only tested on Ubuntu 64bits.

Update: It is difficult to count the number of instructions inside the loop on the hot path. It is certainly below 100, don't know if I have been able to reach the 50 I have predicted... I blame gcc -O3 for that for unrolling small loops as the key comparison.

In reply to Re^9: Can you improve upon my algorithm. by salva
in thread Can you improve upon my algorithm. by BrowserUk

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