Debug a Lustre program with rdbg

This Tiny Tutorial shows a basic usage of rdbg to debug a Lustre program.

Consider this Lustre program, which computes a sinus and a cosinus wave in a discrete manner.

node sincos(omega : real) returns (sin, cos: real);
var pcos, psin: real;
let
  pcos = 1.0 fby cos;
  psin = 0.0 fby sin;
  sin = omega * integrator( pcos,0.1,0.0);
  cos = omega * integrator(-psin,0.1,1.0);
tel
node integrator(F,STEP,init: real) returns (Y: real);
let
  Y = init -> pre(Y) + ((F + pre(F))*STEP)/2.0;
tel

One can simulate this node:

lv6 sincos.lus -n sincos -exec

In order to avoid the need of providing an input to the sincos node, we will run a simpler node sincos_test, with no input.

node sincos_test() returns (sin, cos: real);
let
  sin,cos=sincos(0.2);
tel

Now to simulate this node during 1500 steps, and output the generated Data in a RIF file named sincos.rif, one can use lurette as follows:

lurette -sut "lv6  sincos.lus -n sincos_test"  -l 1500 -o sincos.rif

gnuplot-rif sincos.rif

In order to inpect the execution of this node (typically for debug), one just need to replace lurette by rdbg.

rdbg -sut "lv6  sincos.lus -n sincos_test" -l 1500 -o sincos.rif

Then at the rdbg prompt, you can type l to get the list of avalaible commands. For instance, try to type:

n
n
ni 20
b
b
bi 20
cg

The last command ougth to display the call graph computed from the current call. With cgf, you get a pdf where nodes are clickable. Then, if you type s (move forward of one step), the values on the callgraphs wires ougth to change.

More on rdbg: http://www-verimag.imag.fr/DIST-TOOLS/SYNCHRONE/rdbg/README.html