#include <stdlib.h>#include <stdio.h>#include <string.h>/* LAPACK */extern int dpotf2_(char *, int *, double *, int *, int *);double dcholfact(int n, double *A, double *L){	/* if A is p.d. , A = L*L'	   if A is p.s.d. , A + lambda*I = L*L'; */  	int indef, i;	static double lambda = 1e-3/512/512;	memcpy(L, A, sizeof(double)*n*n);	dpotf2_("L", &n, L, &n, &indef);	if (indef != 0)	{		memcpy(L, A, sizeof(double)*n*n);		for (i=0;i<n;i++)			L[i*n+i] += lambda; 		dpotf2_("L", &n, L, &n, &indef);		if (indef != 0)		{			printf("A is not positive semi-definite\n");			lambda *= 2;		}		return lambda;	}	return 0;}double dprecond(int n, double *A, double *C){	/* Given a dense symmetric positive semidefinite matrix A, this	subroutine computes the precondictioner C. Use full Cholesky	factorization instead of incomplete Cholesky factorization that	orginal TRON uses. It is the major difference between the two. */	return dcholfact(n, A, C);}