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

7 Jul 2010


      Thanks Alexei

i complicated myself with the archive_node  because i didnt know i could do
this
ex_to<matrix>

best regards,
Cristobal


Cristobal <http://www.youtube.com/neoideo>


On Wed, Jul 7, 2010 at 1:41 AM, Alexei Sheplyakov <
alexei.sheplyakov@gmail.com> wrote:
...
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
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