Commit 5b3c25ab authored by Nguyen, Thien Minh's avatar Nguyen, Thien Minh
Browse files

Syntactic sugar for loop 



Rewrite Python for loops into C++ range-based for loops.

Hence, we can loop directly on python arrays, e.g. list of Pauli terms.

Add C++ range() and len() impl in QCOR utils.

Signed-off-by: default avatarThien Nguyen <nguyentm@ornl.gov>
parent e34245b1

handlers/token_collector/pyxasm/pyxasm_visitor.hpp

+10 −22
Original line number Diff line number Diff line
@@ -152,28 +152,16 @@ public: 


  antlrcpp::Any visitFor_stmt(pyxasmParser::For_stmtContext *context) override {

    auto counter_expr = context->exprlist()->expr()[0];



    if (context->testlist()->test()[0]->getText().find("range") !=

        std::string::npos) {

      auto range_str = context->testlist()->test()[0]->getText();

      auto found_paren = range_str.find_first_of("(");

      auto range_contents = range_str.substr(

          found_paren + 1, range_str.length() - found_paren - 2);



    auto iter_container = context->testlist()->test()[0]->getText();

    // Rewrite:

    // Python: "for <var> in <expr>:"

    // C++: for (auto& var: <expr>) {}

    // Note: we add range(int) as a C++ function to support this common pattern.

    std::stringstream ss;

      ss << "for (int " << counter_expr->getText() << " = 0; "

         << counter_expr->getText() << " < " << range_contents << "; ++"

         << counter_expr->getText() << " ) {\n";



    ss << "for (auto &" << counter_expr->getText() << " : " << iter_container

       << ") {\n";

    result.first = ss.str();

    in_for_loop = true;



    } else {

      xacc::error(

          "QCOR PyXasm can only handle 'for VAR in range(QREG.size())' at the "

          "moment.");

    }



    return 0;

  }

python/examples/qaoa_circuit.py

+3 −5
Original line number Diff line number Diff line
@@ -15,13 +15,11 @@ def qaoa_circ(q: qreg, cost_ham: PauliOperator, nbSteps: int, theta: List[float] 
    

    terms = cost_ham.getNonIdentitySubTerms()

    for step in range(nbSteps):

        # TODO: this looks weird (terms is a vector)

        # we need to support Pythonic len() method

        for i in range(terms.size()):

            exp_i_theta(q, theta[step], terms[i])

        for term in terms:

            exp_i_theta(q, theta[step], term)



        # Reference Hamiltonian: 

        for i in range(q.size()):

        for i in range(len(q)):

            ref_ham_term = X(i)

            exp_i_theta(q, beta[step], ref_ham_term)

runtime/utils/qcor_utils.hpp

+10 −0
Original line number Diff line number Diff line
@@ -57,6 +57,16 @@ template <typename T> std::vector<T> linspace(T a, T b, size_t N) { 
  return xs;

}



inline std::vector<int> range(int N) {

  std::vector<int> vec(N);

  std::iota(vec.begin(), vec.end(), 0);

  return vec;

}



// Get size() of any types that have size() implemented.

template <typename T> int len(const T &countable) { return countable.size(); }

template <typename T> int len(T &countable) { return countable.size(); }



// The TranslationFunctor maps vector<double> to a tuple of Args...

template <typename... Args>

using TranslationFunctor =