Re: Bad expression parsing/evaluation

[Domingo Alvarez Duarte]

Definitely the way GMPL/GLPK calculates the modulo of a negative number 
is wrong:

====

param a := 4;
param b := 3;
param c := a mod b;
param d := a - c;


param a2 := -4;
param b2 := 3;
param c2 := a2 mod b2;
param d2 := a2 - c2;

display a, b, c, d, a2, b2, c2, d2;

====

AMPL output:

====

ampl test4.ampl
a = 4
b = 3
c = 1
d = 3
a2 = -4
b2 = 3
c2 = -1
d2 = -3

====

GMPL/GLPK/GLPSOL output:

====

glpsol -m test4.ampl
GLPSOL: GLPK LP/MIP Solver, v4.65-ex, glp_double size 8
Parameter(s) specified in the command line:
 -m test4.ampl
Reading model section from test4.ampl...
test4.ampl:12: warning: unexpected end of file; missing end statement 
inserted
12 lines were read
Display statement at line 12
a = 4
b = 3
c = 1
d = 3
a2 = -4
b2 = 3
c2 = 2
d2 = -6

...

====

Cheers !

On 15/8/21 16:50, Heinrich Schuchardt wrote:
> On 8/15/21 4:06 PM, Domingo Alvarez Duarte wrote:
> > Comparing how AMPL and GMPL calculate random expressions I found some of
> > then where they differ or GMPL can't manage see bellow, also one of then
> > that references itself makes glpsol segfault but ampl gives an error
>
> I can't see a segfault with GLPK 5.0.
>
> Please, use gdb to identify in which line of code it occurs:
>
>     gdb --args glpk -m test.od
>
> > message explaining the problem:
> >
> > ====
> >
> > param a0 := (((((((788)*(8.46))))+8342*1.803-1))*4186.4*(15));
> > printf "%f\n", a0;
> >
> > param a1 := (((22 mod 284/((7530/((2)*(((((25))-421))))))*597 mod
> > 2663)+7283.8-9.60+167 mod ((3))))+(8871);
> > printf "%f\n", a1;
> >
> > #param a2 := a1 * a2; #glpsol segfault
> > param a2 := a0 * a1;
> > printf "%f\n", a2;
> >
> > param a = (((((((788)*(8.46))))+8342*1.803-1))*4186.4*(15))*(((22 mod
>
> Your syntax is wrong. This should be:
>
> param a :=
>
> With correct syntax:
>
> glpsol -m /tmp/test.mod
> GLPSOL: GLPK LP/MIP Solver, v4.65
> Parameter(s) specified in the command line:
>  -m /tmp/test.mod
> Reading model section from /tmp/test.mod...
> 28 lines were read
> 1363056632.376000
> 17428.775299
> 23756407765226.851562
> 11664732388290.359375
> 11665910614443.386719
> 8259816920615.111328
> 8259816920615.111328
> Model has been successfully generated
>
> Best regards
>
> Heinrich
>
> > 284/((7530/((2)*(((((25))-421))))))*597 mod 2663)+7283.8-9.60+167 mod
> > ((3))))+(8871);
> > #param a := 3+2;
> > printf "%f\n", a;
> >
> > param b = (((((((788)*(8.46))))+8342*1.803-1))*4186.4*(15))*(((22 mod
> > 284/((7530/((2)*(((((25))-421))))))*597 mod 2663)+7283.8-9.60+167.8644
> > mod ((3))))+(8871);
> > #param a := 3+2;
> > printf "%f\n", b;
> >
> > param c =
> > (((((((788)*(8.46))))+8342*1.803-1))*4186.4*(15))*(((22/((7530/((2)*(((((25))-421))))))*597)+7283.8-9.60+167))+(8871); 
> >
> >
> > #param a := 3+2;
> > printf "%f\n", c;
> >
> > param d =
> > (((((((788.0)*(8.46))))+8342.0*1.803-1.0))*4186.4*(15.0))*(((22.0/((7530.0/((2.0)*(((((25.0))-421))))))*597.0)+7283.8-9.60+167.0))+(8871.0); 
> >
> >
> > #param a := 3+2;
> > printf "%f\n", d;
> >
> > ====
> >
> > AMPL output:
> >
> > ====
> >
> > ampl test.ampl
> > 1363056632.376000
> > 14765.775299
> > 20126587953209.562500
> > 8034912576273.071289
> > 8036090802426.097656
> > 8259816920615.111328
> > 8259816920615.111328
> >
> > ====
> >
> > GLPSOL output:
> >
> > ====
> >
> > glpsol -m test.ampl
> > GLPSOL: GLPK LP/MIP Solver, v4.65
> > Parameter(s) specified in the command line:
> >   -m test.ampl
> > Reading model section from test.ampl...
> > test.ampl:25: warning: unexpected end of file; missing end statement
> > inserted
> > 25 lines were read
> > 1363056632.376000
> > 17428.775299
> > 23756407765226.851562
> > test.ampl:13: no value for a
> > MathProg model processing error
> >
> > ====
> >
> > With a incorrect expression:
> >
> > ====
> >
> > param a2 := a1 * a2; #glpsol segfault
> > #param a2 := a0 * a1;
> >
> > ====
> >
> > AMPL output:
> >
> > ====
> >
> > ampl test.ampl
> > 1363056632.376000
> > 14765.775299
> >
> > test.ampl, line 7 (offset 228):
> >      a2 is not defined
> > context:  param a2 := a1 *  >>> a2; <<< #glpsol segfault
> >
> > ====
> >
> > GLPSOL output:
> >
> > ====
> >
> > glpsol -m test.ampl
> > GLPSOL: GLPK LP/MIP Solver, v4.65
> > Parameter(s) specified in the command line:
> >   -m test.ampl
> > Reading model section from test.ampl...
> > test.ampl:25: warning: unexpected end of file; missing end statement
> > inserted
> > 25 lines were read
> > 1363056632.376000
> > 17428.775299
> > Segmentation fault (core dumped)
> >
> > ====
> >
> > Cheers !