programming


C/C++: How to round up a number

#include 
intergerVariable = ceil (floatVariable);

To compile with math.h library you MUST include the -lm flag.

gcc -lm main.c


C/C++: Capture stdout from a system() command

	FILE *results;
	int queen;
	if (!(results = popen("./precosat -f nqueens.cnf | tail -n +2 | head -n -1 | tr -d v | tr ' ' '\n' | grep -v '^$' | grep ^[0-9]", "r"))) {
		cout << "Unable to Execute Precosat" << endl << "./precosat -f nqueens.cnf | tail -n +2 | head -n -1 | tr -d v | tr ' ' '\n' | grep -v '^$' | grep ^[0-9]" << endl;
		exit(1);
	}
	for (i = 0; i < queens; i++) {
		fscanf(results,"%d",&queen);
		cout << "Queen #" << i+1 << " goes to [" << ((queen%queens)?(queen%queens):queens) << "]" << endl;
	}
	pclose(results);

Above, you will find an example that was used to extract data from the PrecoSAT SAT Solver in order to solve the N-Queens problem. It returns all positive variables, one per line.

You can see that after the call to popen, it creates a pointer to a file stream that can be used as a regular file to read the data from the called process.


Ubuntu: How to compile PrecoSAT v.570 under ubuntu 11.10

By downloading PrecoSAT from http://fmv.jku.at/precosat/ and trying to install it on Ubuntu 11.10 32-bit (Oneiric Ocelot) by:

    • Decompressing the files
    • and calling ./configure && make

I got the following error at make:

g++ -O3 -m32 -static -Wall -Wextra -DNDEBUG -DNLOGPRECO -DNSTATSPRECO  -c precomain.cc
In file included from precomain.cc:23:0:
precosat.hh:164:31: error: ‘ptrdiff_t’ has not been declared
precosat.hh:270:13: error: ‘ptrdiff_t’ has not been declared
make: *** [precomain.o] Error 1

which can be resolved by adding

#include <cstddef>

at the includes in the file precosat.hh