C++ 用LAPACK计算无限带状矩阵的特征值
你知道我哪里会出错吗C++ 用LAPACK计算无限带状矩阵的特征值,c++,lapack,eigenvalue,C++,Lapack,Eigenvalue,你知道我哪里会出错吗 #include <iostream> #include <algorithm> #include <string> #include <math.h> using namespace std; //SUBROUTINE DSBTRD( VECT, UPLO, N, KD, AB, LDAB, D, E, Q, LDQ, WORK, INFO ) extern "C" { void dsbtrd_(const char
#include <iostream>
#include <algorithm>
#include <string>
#include <math.h>
using namespace std;
//SUBROUTINE DSBTRD( VECT, UPLO, N, KD, AB, LDAB, D, E, Q, LDQ, WORK, INFO )
extern "C" {
void dsbtrd_(const char *vect, const char *uplo, int *n, int *kd, double *ab, int *ldab, double d[], double e[], double *q, int *ldq, double work[], int *info);
}
#define MAX 14
int main(){
// Values needed for dsbtrd
const char *vect = "V";
const char *uplo = "U";
int n;
int ldab = MAX;
int ldq = MAX;
int info;
double ab[MAX][ldab];
double d[MAX];
double e[MAX];
double q[MAX][ldq];
double work[MAX];
//other values needed
int i,j,delta;
double eps;
double a[MAX][MAX];
double g[MAX][MAX];
//Read in value of eps and n
cout <<"Enter epsilon: \n";
cin >> eps;
cout << "Epsilon = " << eps << "\n";
cout <<"Enter n: \n";
cin >> n;
cout << "n = " << n << "\n";
if(n >= MAX){
cerr << "n is great than max \n";
}
//Build matrix g
for(j = 0; j < n; j++){
for(i = 0; i < n; i++){
int m = min(i,j);
if(i == j){
g[i][j] = 1.5*(pow(m,2) + m +.5);
}else if( i == j + 2 || i == j - 2){
g[i][j] = (m + 1.5)*sqrt((m+1)*(m+2));
}else if(i == j + 4 || i == j -4){
g[i][j] = .25*sqrt((m+1)*(m+2)*(m+3)*(m+4));
}else{
g[i][j] = 0;
}
}
}
//Build the starting matrix a
//row i, column j
for(j = 0; j < n; j++){
for(i = 0; i < n; i++){
if(i == j){
delta = 1;
}else{
delta = 0;
}
a[i][j] = (i + .5)*delta + eps*g[i][j];
}
}
//Build the matrix ab
// ab(kd+1+i-j,j) = a(i,j) for max(1,j-kd)<=i<=j
int kd = n - 1;
for(j = 1; j <= n; j++){
for(i = max(1,j-kd); i <= j; i++){
ab[j-1][kd+i-j] = a[j-1][i-1];
}
}
//Solve for eigenvalues
dsbtrd_(vect, uplo, &n, &kd, &ab[0][0], &ldab, d, e, &q[0][0], &ldq, work, &info);
//Check for success
if(info == 0)
{
//Write answer
for(i = 0; i < n; i++){
cout << "Eigenvalue " << i << ": " << d[i] << "\n";
}
}
else
{
//Write error
cerr << "dsbtrd returned error " << info << "\n";
}
return info;
}
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使用名称空间std;
//子例程DSBTRD(VECT、UPLO、N、KD、AB、LDAB、D、E、Q、LDQ、WORK、INFO)
外部“C”{
无效dsbtrd_389;(常量字符*向量,常量字符*上传,int*n,int*kd,double*ab,int*ldab,double d[],double e[],double*q,int*ldq,double work[],int*info);
}
#定义最大值14
int main(){
//dsbtrd所需的值
常量字符*vect=“V”;
常量字符*uplo=“U”;
int n;
int ldab=最大值;
int ldq=最大值;
国际信息;
双ab[MAX][ldab];
双d[MAX];
双e[MAX];
双q[MAX][ldq];
双功[最大值];
//所需的其他值
inti,j,delta;
双每股收益;
双a[MAX][MAX];
双g[MAX][MAX];
//读取eps和n的值
cout-eps;
coutDSBTRD不计算特征值。它将矩阵简化为三对角形式;您将结果三对角矩阵的主对角线拉出,并假装这些是特征值,但它们不是
您需要在生成的三对角形式上调用DSTERF(或其他一些例程之一)以获得特征值
有关更多详细信息,请参阅。我认为您的矩阵内存布局与LAPACK使用的不匹配。如果内存可用,您需要一个一维数组。您正在使用的函数的文档会告诉您如何索引到该数组中。我最后使用了DSYEV
,这对我所做的工作起到了作用。感谢您的回答!