how the sequence is run on sequencer

Nothing new in this post but just wanted to put together what i was going through yday about the sequences/sequencers and how they are started:

so we will have a sequence written something like

class random_seq extends uvm_sequence;
  `uvm_object_utils(random_seq)
::::
::::
endclass:random_seq

and in the test we will start the sequence by using uvm_config_db set method, something like:

configuration by type:
uvm_config_db#(uvm_object_wrapper)::set(this, "m_tb.m_agent.m_sequencer.main_phase", "default_sequence", random_seq::get_type());

or something like:

Configuration by instance:
random_seq m_rand_seq_inst;
m_rand_seq_inst = new("m_rand_seq_inst");
uvm_config_db#(uvm_sequence_base)::set(this, "m_tb.m_agent.m_sequencer.main_phase", "default_sequence", m_rand_seq_inst);

above setting will call the following task from the uvm_sequencer_base class and it is called in " protected virtual function void execute" function of uvm_task_phase class.

function void uvm_sequencer_base::start_phase_sequence(uvm_phase phase);
    uvm_object_wrapper wrapper;
  .......
   seq.start(this);

  ......

endfunction

protected virtual function void execute(uvm_component comp,

                                          uvm_phase phase);

...............

    if ($cast(seqr,comp))   // Only if the component is sequencer then the start_phase_sequence is called 

                                       // otherwise its ignored. 

          seqr.start_phase_sequence(phase);

...............

endfunction

the execute function is called inside
 function void m_traverse(uvm_component comp,
                           uvm_phase phase,
                           uvm_phase_state state);

 case (state)
 ....

   UVM_PHASE_EXECUTING: begin

....

   ph.execute(comp, phase);

....

 end

 ....

 endcase

endfunction

m_tranverse is called in traverse function of uvm_task_phase

  virtual function void traverse(uvm_component comp,

                                 uvm_phase phase,

                                 uvm_phase_state state);

    phase.m_num_procs_not_yet_returned = 0;

    m_traverse(comp, phase, state);

  endfunction

which is called in uvm_phase s task

task uvm_phase::execute_phase();

......

  m_state = UVM_PHASE_STARTED;

    m_imp.traverse(top,this,UVM_PHASE_STARTED);

    #0; // LET ANY WAITERS WAKE UP

.......

endtask

and the execute+phase is called as a part of m_run_phases task of uvm_phase

 task uvm_phase::m_run_phases();

  uvm_root top = uvm_root::get();

 .....

  fork

      begin

        phase.execute_phase();

      end

    join_none

.....

endtask

this m_run_phases task is called in run_test task of uvm_root from which all the tests are run and all the components are instantiated.

task uvm_root::run_test(string test_name="");

................

 // phase runner, isolated from calling process

  fork begin

    // spawn the phase runner task

    phase_runner_proc = process::self();

    uvm_phase::m_run_phases();

  end

  join_none

...............

endtask

and the run_test with which the testcase is run

the explanation for run_test:

  // Phases all components through all registered phases. If the optional

  // test_name argument is provided, or if a command-line plusarg,

  // +UVM_TESTNAME=TEST_NAME, is found, then the specified component is created

  // just prior to phasing. The test may contain new verification components or

  // the entire testbench, in which case the test and testbench can be chosen from

  // the command line without forcing recompilation. If the global (package)

  // variable, finish_on_completion, is set, then $finish is called after

  // phasing completes.

other notes:

uvm_object --> uvm_phase --> uvm_task_phase --> all the  uvm_runtime_phases (reset_phase,configure_phase ....)

uvm_phase has the prototype for all the tasks required while executing a phase and uvm_task_phase is derived from it which has some functionality required for executing the phases (things which are common across the phases) 

why its not good to use defines in uvm code in general -2

Continuing from the previous post

found the following paper written by Adam Erickson of Mentor Graphics

This papers gives an idea about what are the macros that can be used and what are the ones which should be avoided

http://verificationhorizons.verificationacademy.com/volume-7_issue-2/articles/stream/are-ovm-and-uvm-macros-evil-a-cost-benefit-analysis_vh-v7-i2.pdf