Hello,
I recently realized that I should be using "-march=native" flag for optimal
performance of matrix-free codes. The application that I've been using
works fine with just SSE2, but with AVX enabled I'm getting a segfault.
Step-48 works fine, so I don't think it is an installation issue.
The function where it occurs is similar to the "local_apply" function in
step 48:
template <int dim>
void getRHS(const MatrixFree<dim,double> &data,
std::vector<dealii::parallel::distributed::Vector<double>*> &dst,
const std::vector<dealii::parallel::distributed::Vector<double>*> &
src,
const std::pair<unsigned int,unsigned int> &cell_range) const{
//initialize FEEvaulation objects
std::vector<typeScalar> scalar_vars;
for (unsigned int i=0; i<num_var; i++){
typeScalar var(data, i);
scalar_vars.push_back(var);
}
//loop over cells
for (unsigned int cell=cell_range.first; cell<cell_range.second; ++cell){
// Initialize, read DOFs, and set evaulation flags
scalar_vars[varInfoListRHS[i].index].reinit(cell);
scalar_vars[varInfoListRHS[i].index].read_dof_values_plain(*src[
varInfoListRHS[i].global_var_index]);
scalar_vars[varInfoListRHS[i].index].evaluate(need_value[i],
need_gradient[i], need_hessian[i]); // <--- segfault happens here!
}
unsigned int num_q_points;
num_q_points = scalar_vars[0].n_q_points;
//loop over quadrature points
for (unsigned int q=0; q<num_q_points; ++q){
(etc.)
The segfault happens during the "evaluate" call. GDB tells me that it
happens on line 5478 of /include/deal.II/matrix_free/fe_evaluation.h, in
EvaluatorTensorProduct::apply:
xp[i] = in[stride*i] - in[stride*(mm-1-i)];
Using the debugger to step through EvaluatorTensorProduct::apply, nothing
seems obviously wrong. As expected, all of the vectorized arrays are four
doubles long. The line above evaluates to xp[0]=in[0]-in[1].
Has anyone else had this issue? Does anyone have ideas what the problem
could be, or what I should be looking for?
Thanks!
Steve
System: Cluster running CentOS 7, with Intel Xeon E5-2670 processors, GCC
v5.4.0
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