Instead of manually starting sequences in your test (seq1.start(sqr) followed
by seq2.start(sqr)), you can bundle them into a Library.
The uvm_sequence_library class can then handle the selection logic for you.
UVM Sequence Libraries
A powerful mechanism to group related sequences and automatically select them for execution strategies like Random, Round-Robin, or User-Defined.
Why Use a Sequence Library?
Defining a Library
Simply extend uvm_sequence_library and register other sequences to it.
class my_seq_lib extends uvm_sequence_library #(my_transaction);
`uvm_object_utils(my_seq_lib)
`uvm_sequence_library_utils(my_seq_lib) // Helper macro
function new(string name="my_seq_lib");
super.new(name);
init_sequence_library();
endfunction
// Register sequences that belong to this library
virtual function void init_sequence_library();
add_typewide_sequence(seq_read::get_type());
add_typewide_sequence(seq_write::get_type());
add_typewide_sequence(seq_reset::get_type());
endfunction
endclassUsing the Library in a Test
In your test, you set the sequencer's default_sequence to be your library.
You can also configure Selection Mode and Count.
class my_test extends uvm_test;
// ...
function void build_phase(uvm_phase phase);
super.build_phase(phase);
// 1. Set the default sequence to run the library
uvm_config_db#(uvm_object_wrapper)::set(this, "env.agent.sqr.run_phase",
"default_sequence", my_seq_lib::get_type());
// 2. Configure the Library (Optional)
// Run 10 sequences from the library
uvm_config_db#(int)::set(this, "env.agent.sqr.run_phase", "count", 10);
// Pick randomly (UVM_SEQ_LIB_RAND) or Cyclic (UVM_SEQ_LIB_ITEM)
uvm_config_db#(uvm_sequence_lib_mode)::set(this, "env.agent.sqr.run_phase",
"selection_mode", UVM_SEQ_LIB_RANDC);
endfunction
endclass
Is this used often?
Honestly, many verification engineers prefer writing explicit Virtual Sequences instead of Sequence Libraries because Virtual Sequences give you precise control (e.g., "Do Reset, then 5 Reads, then 2 Writes"). Sequence Libraries are great for "stress testing" where the order doesn't matter as much as volume.
Honestly, many verification engineers prefer writing explicit Virtual Sequences instead of Sequence Libraries because Virtual Sequences give you precise control (e.g., "Do Reset, then 5 Reads, then 2 Writes"). Sequence Libraries are great for "stress testing" where the order doesn't matter as much as volume.