[GiNaC-list] Store matrix, then read it?

[Alexei Sheplyakov]

Hello,

On Tue, Jul 06, 2010 at 09:05:06PM -0400, Cristobal Navarro wrote:
> 
> i am experiencing a little trouble when reading my stored matrix.
> when i write and read the same matrix i stored, it works.
> but if i only run the program to read the matrix file, i get this error.
> 
> terminate called after throwing an instance of 'std::runtime_error'
>   what():  unknown matrix dimensions in archive
> 

The example below works for me just fine.

#include <string>
#include <fstream>
#include <stdexcept>
#include <ginac/ginac.h>
using namespace std;
using namespace GiNaC;

static void read(const string& filename, matrix& qvCol, matrix& qvMat, const lst& symlst)
{
	archive ar;
	ifstream f(filename.c_str());
	if (!f.is_open())
		throw std::runtime_error(string("Failed to open input file: ") + filename);
	f >> ar;
	f.close();
	ex qvColEx = ar.unarchive_ex(symlst, "qvCol");
	ex qvMatEx = ar.unarchive_ex(symlst, "qvMat");
	if (!(is_a<matrix>(qvColEx) && is_a<matrix>(qvMatEx)))
		throw std::runtime_error("expected a matrix");
	qvCol = ex_to<matrix>(qvColEx);
	qvMat = ex_to<matrix>(qvMatEx);
}

static void write(const string& filename, const matrix& qvCol, const matrix& qvMat)
{
	archive ar;
	ar.archive_ex(qvCol, "qvCol");
	ar.archive_ex(qvMat, "qvMat");
	ofstream f(filename.c_str());
	if (!f.is_open())
		throw std::runtime_error(string("Failed to open output file: ") + filename);
	f << ar << flush;
	f.close();
}

int main(int argc, char** argv)
{
	const symbol q("q"), v("v");
	lst symlst;
	symlst = q, v;

	matrix qvMat(2, 2), qvCol(2, 1);
	qvCol = q*v, 2*q*v;
	qvMat = q*v,	2*q*v,
	        3*q*v,	4*q*v;
	cout << endl << "m1: " << endl << qvCol << endl;
	cout << "m2: " << endl << qvMat << endl << endl;
 
	write("example.gar", qvCol, qvMat);
	matrix rm1, rm2;
	read("example.gar", rm1, rm2, symlst);
	cout << endl << "rm1: " << endl << rm1 << endl;
	cout << "rm2: " << endl << rm2 << endl << endl;
	return 0;
}

> This is a one-file example source code i made for you guys so you can test,
> its based on the same problem i have on my bigger code.
> try running it as it is, then comment the "write" method and run it again so
> it only reads the matrices, youll get the error eventually. but you will
> never get it if you write and read, its weird.

[skipped the code]

> how can this be solved?

First of all, please (re)read the manual, in particular, the (sub)section
called `Archiving'. Secondly, stop abusing read_archive() and archive_node.

Hope this helps,
	Alexei