Use vector of doubles in Args

Question

Hello,

I have a spin chain with a random magnetic field and a very practical way to save my parameters in a file is to save them as Args and use the writetofile() function. I wanted to save the local random magnetic field vector<double> as well but an error occurs. Is it possible that Args takes more inputs than just Vals?

Thank you !

Answer 1

Hi jsf,
While that's a clever way to store and retrieve values, the Args system is really intended to pass named arguments to functions, not as a database to hold arbitrary types. If we made it possible to do so, it would cause an unacceptably high performance penalty to most of the functions using Args and go beyond the intended purpose of that system.

Instead, you can already read and write most types used in ITensor, including standard library types such as std::vector, to files using the read and write functions provided with ITensor. Here is some example code showing how.

Writing objects to a file "myfile.dat":

auto v = vector<int>(4);
v[0] = 1;
v[1] = 3;
v[2] = 5;
v[3] = 9;

auto i = Index("i",2);
auto T = randomTensor(i);

std::ofstream f("myfile.dat",std::ios::binary);
write(f,v);
write(f,i);
write(f,T);
f.close();

Reading the data back in from the file:

std::ifstream f("myfile.dat",std::ios::binary);
vector<int> v;
read(f,v);
Index i;
read(f,i);
ITensor T;
read(f,T);
f.close();

Print(v.size());
Print(v[0]);
Print(v[1]);
Print(v[2]);
Print(v[3]);
Print(T);

Comments

Thank you for your answer. My args are actually the arguments of my class but I'll do the way you recommend