Re: strange problem of sorting

"osmium" <>
Fri, 6 Jul 2007 07:56:00 -0700
"abracadabra" writes:

I am reading an old book - Programming Pearls 2nd edition recently. It
says, "Even though the general C++ program uses 50 times the memory
and CPU time of the specialized C program, it requires just half the
code and is much easier to extend to other problems." in a sorting
problem of the very first chapter.

I modified the codes in the answer part, ran it and found it is almost
the contrary case. The qsortints.c is the C code that uses the qsort
function defined in stdlib.h. The sortints.cpp uses STL sort. The
bitsort.c uses the method of bitmap in the book. To my surprise, the
bitmap method is slowest! The qsort method slower, the sort fastest.
It is totally different from what is said in the book!

I repeated the experiment using Visual Studio 2005 on a Windows XP
machine, and mingw32(gcc 4.2.0), the result is the same:

Here goes the code.

/* qsortints.c -- Sort input set of integers using qsort */
#include <stdio.h>

massive snippage

printf("%d\n", i);*/

return 0;
/* Output is 1.45000 on SuSE */
/* End of bitsort.c */

Any suggestions?

My first question would be, how long did the three methods take in MKS
units? (clocks/sec in not an MKS unit). I think you may be trying to
extract too much information from a small sample. ISTM the author's point
was simply that STL sort was easier to use than qsort. Given a programmer
with sufficient background, I guess that is marginally true.

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