How to configure DSP block in "three 9x9 multipliers" mode?

Dear Mr. Pin

Thank you for your answer.

I've prepared a test project (archive was attached to this message). There are three ways to create a mult in this project. Please comment or uncomment "define" in line 2-5 and check them.

For ways 0 and 2 I have one DSP, but incorrect result, and correct result, but 3 DSPs for a way 1.

Please, give me an example where DSP block works in 3-mult mode. I've seen a lot of beautiful pictures, but I haven't seen any code examples.

Your answer is totally right!

I created this code

`timescale 1ns / 1ns
 
(* multstyle = "dsp" *)
module mux_9x9
#(
	parameter L = 25
)
(
	input logic [8:0] x_0[L],	
	input logic [8:0] x_1[L],
	input logic [8:0] x_2[L],
 
	input logic [8:0] y_0[L],	
	input logic [8:0] y_1[L],
	input logic [8:0] y_2[L],
	
	output logic [17:0] p_0[L],	
	output logic [17:0] p_1[L],
	output logic [17:0] p_2[L]	
);
 
genvar i;
generate
	for( i = 0; i < L; i++ )	
		begin:MULT			
			assign {p_0[i],p_1[i],p_2[i]} = {x_0[i]*y_0[i],x_1[i]*y_1[i],x_2[i]*y_2[i]};				
		end	
endgenerate
	
endmodule

Quartus places three multi to one DSP when it doesn't have enough DSP (just change parameter "L").