modelsim crashs with large ram simulation model

[Hongtu]

I 'd like to simulate my design with a memory simulation model.
The vhdl for memory model is like this:

-------------------------------------------------------------------------------
constant weight_L : integer := 16;
constant mean_L : integer := 28;
constant variance_L : integer := 24;

type Gauss_parameters is record
weight : std_logic_vector(weight_L-1 downto 0);
mean1 : std_logic_vector(mean_L-1 downto 0);
mean2 : std_logic_vector(mean_L-1 downto 0);
mean3 : std_logic_vector(mean_L-1 downto 0);
variance : std_logic_vector(variance_L-1 downto 0);
end record;
type ram_data_type is array (0 to 352*288*9) of Gauss_parameters;
signal ram_data : ram_data_type;


-------------------------------------------------------------------------------

whenever I use modelsim to start simulation, the memory uesed by modelsim
will exceed 4G memory, and modelsim crashs. I am using Sun server with 16G
RAM. Can anyone tell me whether it is the problem of my design or the bug with
modelsim. Is there another way to write memory simulation model that uses much
less memory during simulation?

/hongtu

 

[Paul Uiterlinden]

Hongtu wrote:

I 'd like to simulate my design with a memory simulation model.
The vhdl for memory model is like this:

-------------------------------------------------------------------------------
constant weight_L : integer := 16;
constant mean_L : integer := 28;
constant variance_L : integer := 24;

type Gauss_parameters is record
weight : std_logic_vector(weight_L-1 downto 0);
mean1 : std_logic_vector(mean_L-1 downto 0);
mean2 : std_logic_vector(mean_L-1 downto 0);
mean3 : std_logic_vector(mean_L-1 downto 0);
variance : std_logic_vector(variance_L-1 downto 0);
end record;
type ram_data_type is array (0 to 352*288*9) of Gauss_parameters;
signal ram_data : ram_data_type;

Yikes, a signal!

Use a variable (in a process) instead. A signal takes much more memory
because it has to drag along a complete event queue and all its
attributes. A variable is much more light weight (up to a factor of ten,
if I'm not mistaken).

Still, the amount of memory will be quite large. Your array will take
113135616 (107M) std_logic bits. Using naturals for the record members
will improve this.

Paul.

 

[Hongtu]

Thank you guys! when I change the signal to variables, everything works smoothly.


/hongtu