A Verilator/Icarus Benchmark

John Bryan

• A performance benchmark of testing unsigned multiplier Verilog of various size is carried out.



• The two testing tools are:
  1. Verilator using a C++ testbench.
  2. Icarus Verilog using a Verilog testbench.



• For increasing multiplier product bit lengths, the multiplier is tested for all possible input combinations.



• The test script is written in Perl. The Perl script, for increasing multiplicand/multiplier bit lengths, performs the following actions:
  1. Generate the unsigned Wallace multiplier Verilog.
  2. Generate the Verilog testbench.
  3. Time the testing of the multiplier for all input combinations using Icarus Verilog.
  4. Generate the C++ Verilator testbench.
  5. Time the testing of the multiplier for all input combinations using Verilator.
  The timed tests are done for increasing multiplier/multiplicand bit lengths and plotted. The times are the combined compilation and simulation times.



• Perl implementation.



• The Perl script takes three arguments.
  1. multiplicand size.
  2. multiplier size.
  3. The number of increasing input operand sizes to be tested. The sizes of the multiplier and multiplicand will increment by one bit in an alternate manner.
     • Example command: perl wallace_benchmark.pl 6 6 8



• Sample output:
  • Unsigned Wallace Verilog.
  • Corresponding Verilog testbench.
  • Corresponding C++ testbench.



• Results: