code: def check_force_gemv_init():
      if check_force_gemv_init._force_init_beta is None:
          from theano.gof.cmodule import GCC_compiler
  
          """
          Test issue 1569.
          Namely when evaluating
  
              beta*y + alpha*dot(A, x)
  
          where we set y * beta = zeros of the correct dimensions we
          do not actually set y = zeros and instead let the BLAS
          perform beta*y with uninitialized memory for
          speed. Occasionally the memory contains values that are
          equivalent to NaN in which case the product beta*y contains
          NaN's for correctly implemented BLAS libraries. In this
          situation, since we are introducing the NaN's, we need to test
          whether the BLAS performs correctly. If it *does*, i.e. it
          actually performs the multiplication beta*y which will result
          in NaN's in the result, then we need intialize the memory to
          zeros.
          """
          test_code = """
  #include <math.h>
  extern "C" void dgemv_(char*, const int*, const int*, const double *, const double *, const int*, const double *, const int*, const double *, double *, const int *);
  int main() {
    double A[2][2] = {{1., 1.}, {1., 1.}};
    double x[2] = {1., 1.};
    double y[2] = {NAN, NAN};
    const int s = 2;
    const int inc = 1;
    const double alpha = 1.0;
    const double beta = 0.0;
  
    dgemv_("T", &s, &s, &alpha, A, &s, x, &inc, &beta, &y, &inc);
  
    return (isnan(y[0]) || isnan(y[1]) ? 1 : 0;
  }
  """
          res = GCC_compiler.try_compile_tmp(
              test_code,
              tmp_prefix="check_beta_",
              flags=ldflags(libs=True, flags=True, libs_dir=True),
              try_run=True,
          )
          if res:
              if res[0]:
                  check_force_gemv_init._force_init_beta = res[1]
              else:
                  check_force_gemv_init._force_init_beta = False
          else:
              check_force_gemv_init._force_init_beta = False
  
      return check_force_gemv_init._force_init_beta
  
imports: from __future__ import absolute_import, print_function, division
  from theano import config
  from theano.gof.params_type import ParamsType
  from theano.scalar import bool
  from theano.tensor.opt import in2out
  from theano.tensor.blas import ldflags, blas_header_text, blas_header_version
  from theano.tensor.blas import blas_optdb, optdb, local_optimizer
  from theano.tensor.blas import Ger, ger, ger_destructive
  from theano.tensor.blas import Gemv, gemv_inplace, gemv_no_inplace
  from theano.tensor import basic
label_desc: Use image node_id 5 for calling a global function with example usage: check_force_gemv_init() and returns: check_force_gemv_init