C interface

Lambert Simon

9 Feb 2006 9 Feb '06

10:43 p.m.

Hello,

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.

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.

Can you help me by giving me the code to build this linear expression with the C interface and to explain it ?

Thank you in advance.

Simon

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Roberto Bagnara

10 Feb 10 Feb

8:26 a.m.

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; }

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Lambert Simon
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