+XBT_PRIVATE boost::intrusive_ptr<simgrid::kernel::activity::ExecImpl>
+SIMIX_execution_start(smx_actor_t issuer, const char* name, double flops_amount, double priority, double bound);
+XBT_PRIVATE boost::intrusive_ptr<simgrid::kernel::activity::ExecImpl>
+SIMIX_execution_parallel_start(const char* name, int host_nb, sg_host_t* host_list, double* flops_amount,
+ double* bytes_amount, double amount, double rate, double timeout);
+