Lambert Simon wrote:
I use the C interface of the Parma Polyhedra Library but I have some
problems to build a linear expression. I want to build the linear expression
"x_1 + 5x_3 - 100 >= 0" for example but I do not arrive.
Dear Simon,
I guess you meant `I want to build the linear expression
"x_1 + 5x_3 - 100"'.
I do "ppl_new_Linear_Expression _with_dimension(&ple, (ppl_dimension_type)
4);" and after I want to add the values to the variables by using the
"ppl_Linear_Expression_add_to_coefficient(ple, coefficient_index[i],
ppl_coeff);" function but that doesn't go.
I don't understand how we can build a linear expression just using this 2
functions.
Why 2? You are overlooking several functions that allow building linear
expressions: you will find them all in the user's manual (pages 34 and 35
of ppl-user-0.8.pdf).
Can you help me by giving me the code to build this linear expression with
the C interface and to explain it ?
I attach under the signature some example code doing what you want.
Use it as follows:
$ gcc sample.c -lppl_c -lppl -lgmpxx -lgmp
$ ./a.out
x_1 + 5*x_3 - 100
If, after reading the manual, you need further advice or explanations,
please come back to us.
All the best,
Roberto
--
Prof. Roberto Bagnara
Computer Science Group
Department of Mathematics, University of Parma, Italy
http://www.cs.unipr.it/~bagnara/
mailto:bagnara@cs.unipr.it
#include <ppl_c.h>
#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
static mpz_t tmp_z;
static void
init_globals() {
mpz_init(tmp_z);
}
static void
deinit_globals() {
mpz_clear(tmp_z);
}
static int
assign_Coefficient_from_int(ppl_Coefficient_t dst, int src) {
mpz_set_si(tmp_z, src);
return ppl_assign_Coefficient_from_mpz_t(dst, tmp_z);
}
static const char*
my_variable_output_function(ppl_dimension_type d) {
static char buffer[20];
int r = sprintf(buffer, "x_%d", d+1);
if (r < 0)
return 0;
else if (r >= 19) {
errno = ERANGE;
return 0;
}
return buffer;
}
int
main() {
int x_1 = 0;
/* int x_2 = 1; */
int x_3 = 2;
/* int x_4 = 3; */
ppl_Coefficient_t coeff;
ppl_Linear_Expression_t le;
ppl_initialize();
init_globals();
ppl_new_Coefficient(&coeff);
ppl_new_Linear_Expression_with_dimension(&le, 4);
/* le += 1*x_1 */
assign_Coefficient_from_int(coeff, 1);
ppl_Linear_Expression_add_to_coefficient(le, x_1, coeff);
/* le += 5*x_3 */
assign_Coefficient_from_int(coeff, 5);
ppl_Linear_Expression_add_to_coefficient(le, x_3, coeff);
/* le += -100 */
assign_Coefficient_from_int(coeff, -100);
ppl_Linear_Expression_add_to_inhomogeneous(le, coeff);
if (ppl_io_set_variable_output_function(my_variable_output_function) < 0) {
fprintf(stderr, "cannot install the custom variable output function\n");
exit(1);
}
ppl_io_print_Linear_Expression(le);
ppl_delete_Linear_Expression(le);
ppl_delete_Coefficient(coeff);
deinit_globals();
ppl_finalize();
return 0;
}
