GLPK/IAJAAR.H project

This page describes a C++ class that wraps the C-style GLPK vectors ia, ja, and ar. The class can be used directly with C++ or via language bindings for Java and R created with SWIG. IAJAAR.H project IAJAAR.H is a small project that provides the specialized triple container class IAJAAR. The purpose of this C++ class is to offer more convenient problem build calls than those available using straight C code. The author is Nigel Galloway. C++ class IAJAAR definition The C++ IAJAAR class definition is: // File: 'iajaar.h' // Provides: C++ class 'IAJAAR' class IAJAAR { private: int * xia; int * xja; double * xar; int entry; int maxSize; public: ~IAJAAR(); // destructor, deallocate memory IAJAAR(int s); // constructor, s is maximum array length const int * ia(); // return C-style int array const int * ja(); // return C-style int array const double * ar(); // return C-style double array void Add(int row, int col, double value); int ne(); // return number of entries }; The member function IAJAAR::Add adds 3-tuples (triples) in the form (row, col, value). The respective arrays can be later retrieved using the member functions IAJAAR::ia, IAJAAR::ja, and IAJAAR::ar. The member function IAJAAR::ne returns the current number of entries. IAJAAR is designed to work with the following GLPK routine: void glp_load_matrix(glp_prob *lp, int ne, const int ia[], const int ja[], const double ar[]); It would be possible to reformulate class IAJAAR using std::vectors internally. That would omit the need to pre-specify the maximum size s in advance, although an optional hint could be given. C++ usage Usage with C++ is straightforward — no special language bindings are required. A description of the underlying problem is can be found on the project website. // File: 'igst10yo.cpp' // An example of using IAJAAR.H with GLPK in C++. // Usage: 'igst10yo.cpp 6.5 7' will calculate 6.5 divided by 7. // Nigel Galloway / July 2009 #include <iostream> #include <stdlib.h> #include "iajaar.h" // see above on wikipage #include "glpk.h" int main(int argc, char * argv[]) { double Q = atof(argv[1]); int N = atoi(argv[2]); IAJAAR * igst10yo = new IAJAAR(5*N); glp_prob * lp = glp_create_prob(); // col 1 is M // cols 2 .. N+1 is a sample of N numbers which sum to Q // cols N+2 .. 2*N+1 are v[1..N] glp_add_rows(lp,N+2); glp_add_cols(lp,2*N+1); for(int i=1; i<=2*N+1; i++) glp_set_col_bnds(lp,i,GLP_FR,0,0); glp_set_row_bnds(lp,N+1,GLP_FX,Q,Q); glp_set_row_bnds(lp,N+2,GLP_FX,0,0); try { for(int i=1; i<=N; i++) { glp_set_row_bnds(lp,i,GLP_FX,0,0); igst10yo->Add(i,i+1,-1); igst10yo->Add(i,1,1); igst10yo->Add(i,i+N+1,1); igst10yo->Add(N+1,i+1,1); igst10yo->Add(N+2,i+N+1,1); } } catch (char * error) { std::cout << error << std::endl; } glp_load_matrix(lp,igst10yo->ne(),igst10yo->ia(),igst10yo->ja(),igst10yo->ar()); glp_simplex(lp,NULL); double Result = glp_get_col_prim(lp,1); std::cout << "The arithmetic mean of a sample of " << N << " numbers whose sum is " << Q << " is " << Result << std::endl; delete igst10yo; glp_delete_prob(lp); return 0; } Python usage IAJAAR can be used with Python. This February 2011 posting explains more. Java usage Java usage requires dedicated language bindings. Unlike the C++ example, Q and N are hardcoded. /* File: 'gmst10yo.java' Usage: 'java -classpath IAJAAR_JAVA.jar;GLPK_JAVA.jar;. gmst10yo' will calculate 22 divided by 7. Modify Q and N below to try alternatives. Nigel Galloway / July 2009 */ import org.gnu.glpk.*; public class gmst10yo { static { System.loadLibrary("IAJAAR_JAVA"); } public static void main(String argv[]) { double Q = 22; int N = 7; IAJAAR t = new IAJAAR(3*N); glp_prob lp = GLPK.glp_create_prob(); GLPK.glp_add_rows(lp,N+1); /* col 1 is M cols 2 .. N+1 are S[n] */ GLPK.glp_add_cols(lp,N+1); for(int i=1; i<=N+1; i++) GLPK.glp_set_col_bnds(lp,i,GLPK.GLP_FR,0,0); t.Add(1,1,1); t.Add(1,2,1); t.Add(N+1,2,1); GLPK.glp_set_row_bnds(lp,N+1,GLPK.GLP_FX,0,0); GLPK.glp_set_row_bnds(lp,1,GLPK.GLP_FX,Q,Q); for(int i=2; i<=N; i++){ GLPK.glp_set_row_bnds(lp,i,GLPK.GLP_FX,0,0); t.Add(i,1,1); t.Add(i,i+1,1); t.Add(N+1,i+1,1); } GLPK.glp_load_matrix(lp,t.ne(),t.ia(),t.ja(),t.ar()); GLPK.glp_simplex(lp,null); double Result = GLPK.glp_get_col_prim(lp,1); GLPK.glp_delete_prob(lp); System.out.println("The arithmetic mean of a sample of " + N + " numbers which sum to " + Q + " is " + Result); } } R usage R usage requires dedicated language bindings. Unlike the C++ example, Q and N are hard-coded. # File: 'gist10yo.R' # Nigel Galloway / July 2009 dyn.load(paste("GLPK_R", .Platform$dynlib.ext, sep="")) source("GLPKconstants.R") source("GLPK_R.R") cacheMetaData(1) Q <- 22 N <- 7 t <- IAJAAR(6) lp <- glp_create_prob() glp_add_rows(lp,3) # col 1 is M # col 2 is v1 # col 3 is v2 glp_add_cols(lp,3) glp_set_col_bnds(lp,1,GLP_FR,0,0) glp_set_col_bnds(lp,2,GLP_FR,0,0) glp_set_col_bnds(lp,3,GLP_FR,0,0) IAJAAR_Add(t,1,1,1) IAJAAR_Add(t,1,2,1) IAJAAR_Add(t,2,1,1) IAJAAR_Add(t,2,3,1) IAJAAR_Add(t,3,2,1) IAJAAR_Add(t,3,3,N-1) glp_set_row_bnds(lp,1,GLP_FX,Q,Q) glp_set_row_bnds(lp,2,GLP_FX,0,0) glp_set_row_bnds(lp,3,GLP_FX,0,0) loadMatrix(t,lp); delete(t) if (glp_simplex(lp,t)==0) { R <- glp_get_col_prim(lp,1) print(sprintf("The arithmetic mean of a sample of %f numbers which sum to %f is %f",N,Q,R)) } else { print("No solution") } Further information is available from the project website. In particular, the source code for iajaar.cpp is worth reviewing.