#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <string.h>
#include <cilk/cilk.h>
#include <lapacke.h>
#include "matrixlib.h"
#include "tictoc.h"

#define N 2000
double vecnorm1(int n,double x[n]){
    double r=0;
    for(int i=0;i<n;i++){
        r+=fabs(x[i]);
    }
    return r;
}
double matnorm1(int n,double A[n][n]){
    double r=0;
    for(int j=0;j<n;j++){
        double s=0;
        for(int i=0;i<n;i++){
            s+=fabs(A[i][j]);
        }
        if(s>r) r=s;
    }
    return r;
}

double A[N][N];
double B[N],X[N],XX[N],*P[N];
int IP[N];
int main(){
    printf("N=%d\n",N);
//    printf("A=\n"); matprint(N,N,A);
    for(int i=0;i<N;i++){
        for(int j=0;j<N;j++){
            A[i][j]=2.0*random()/RAND_MAX-1.0;
        }
        X[i]=1;
    }
    printf("|A|_1=%g\n",matnorm1(N,A));
    multAx(N,N,A,X,B);  // B=AX
//    printf("B=\n"); vecprint(N,B);
    tic();
//  PLUfact(N,A,P);     // now A contains LU fact
//  PLUsolve(N,A,P,XX,B);
    memcpy(XX,B,sizeof(double)*N);
    LAPACKE_dgesv(LAPACK_ROW_MAJOR,N,1,&A[0][0],N,IP,XX,1);
    double t=toc();
    printf("The elapsed time was %g seconds.\n",t);
    double flops=2.0*(N/3.0+1)*N*N/t;
    printf("The speed is %g GFLOPS.\n",flops/1e9);
//    printf("XX=\n"); vecprint(N,XX);
    double r=0;
    for(int i=0;i<N;i++){
        double rd=XX[i]-1;
        r+=rd*rd;
    }
    r=sqrt(r);
    printf("The error is %g.\n",r);
    return 0;
}