从“How to exit GNU Octave, after running an m file, without closing plot windows?”出来的问题是，是否可以将向量从C程序传递到GNU Octave函数 . 我有这个C程序：
#include <iostream>
#include <vector>
#include <string>
#include <fstream>
#include <cmath>
#include <utility>
#include <unistd.h>
#include <octave/oct.h>
#include <octave/octave.h>
#include <octave/parse.h>
#include <octave/toplev.h>
using namespace std;
double N = 1000.0;
double t0 = 0.0;
double t1 = 10.0;
double x0 = 0.0;
double dx0 = 0.0;
double h = (t1 - t0) / double(N);
double dx2(double t, double x, double dx)
{
return {-9.8*cos(x + dx)};
}
std::pair<double, double> RK4(double t, double x, double dx, double h)
{
// k values are diffs in dy/dx.
// l values are diffs in x.
double k1, k2, k3, k4, l1, l2, l3, l4, diff1, diff2;
k1 = h*dx2(t,x,dx);
l1 = h*dx;
k2 = h*dx2(t+h/2,x+l1/2,dx+k1/2);
l2 = h*(dx+k1/2);
k3 = h*dx2(t+h/2,x+l2/2,dx+k2/2);
l3 = h*(dx+k2/2);
k4 = h*dx2(t+h,x+l3,dx+k3);
l4 = h*(dx+k3);
diff1 = (l1+2*l2+2*l3+l4)/float(6); // diff in x.
diff2 = (k1+2*k2+2*k3+k4)/float(6); // diff in y.
return {diff1, diff2};
}
int main()
{
std::vector<double> t;
t.push_back(t0);
std::vector<double> x;
x.push_back(x0);
std::vector<double> dx;
dx.push_back(dx0);
ofstream myfile;
ofstream myfiledx;
myfile.open("simppenadj.txt");
myfiledx.open("simppenadjdx.txt");
for(int i = 1; i<=N; i++) {
auto diff = RK4(t[i-1],x[i-1],dx[i-1],h);
t.push_back( t[i-1] + h);
x.push_back( x[i-1] + diff.first );
dx.push_back(dx[i-1] + diff.second );
myfile << t[i-1];
myfile << " " << x[i-1] << "\n";
myfiledx << x[i-1];
myfiledx << " " << dx[i-1] << "\n";
usleep(1000);
}
myfile << t[N];
myfile << " " << x[N];
myfile.close();
myfiledx << x[N];
myfiledx << " " << dx[N];
myfiledx.close();
pid_t pid = fork();
if(pid != 0) // parent
{
std::cout << "parent, exiting\n";
}
else
{
// arguments for octave
string_vector argv (2);
argv(0) = "embedded";
argv(1) = "-q"; // quiet
// start octave, run embedded (third parameter == true)
octave_main (2, argv.c_str_vec (), true);
// read the script file
source_file("simppenadj.m");
// call the function with an argument
octave_value_list in;
in(0) = t;
in(1) = x;
in(2) = dx;
feval("simppenadj",in,1);
std::cout << "octave (child process) done\n";
clean_up_and_exit(0); // quit octave. This also quits the program,
// so use this together with atexit, if you
// need to do something else after octave exits
}
}
in(0) ， in(1) 和 in(2) 定义行是此代码中存在问题的位置 . 每当编译该程序并运行错误时：
/usr/bin/g++ -Wall -fPIC -L/usr/lib/octave/4.0.3 -I/usr/include/octave-4.0.3 -loctave -loctinterp -o "simppenadj.o" "simppenadj.cpp" && chmod +x simppenadj.o && ./simppenadj.o
simppenadj.cpp: In function ‘int main()’:
simppenadj.cpp:97:14: error: no match for ‘operator=’ (operand types are ‘octave_value’ and ‘std::vector<double>’)
in(0) = t;
^
In file included from /usr/include/octave-4.0.3/octave/oct-obj.h:33:0,
from /usr/include/octave-4.0.3/octave/ov-fcn.h:31,
from /usr/include/octave-4.0.3/octave/ov-builtin.h:28,
from /usr/include/octave-4.0.3/octave/defun-int.h:28,
from /usr/include/octave-4.0.3/octave/defun-dld.h:30,
from /usr/include/octave-4.0.3/octave/oct.h:36,
from simppenadj.cpp:8:
/usr/include/octave-4.0.3/octave/ov.h:356:17: note: candidate: octave_value& octave_value::operator=(const octave_value&)
octave_value& operator = (const octave_value& a)
^~~~~~~~
/usr/include/octave-4.0.3/octave/ov.h:356:17: note: no known conversion for argument 1 from ‘std::vector<double>’ to ‘const octave_value&’
simppenadj.cpp:98:12: error: no match for ‘operator=’ (operand types are ‘octave_value’ and ‘std::vector<double>’)
in(1) = x;
^
In file included from /usr/include/octave-4.0.3/octave/oct-obj.h:33:0,
from /usr/include/octave-4.0.3/octave/ov-fcn.h:31,
from /usr/include/octave-4.0.3/octave/ov-builtin.h:28,
from /usr/include/octave-4.0.3/octave/defun-int.h:28,
from /usr/include/octave-4.0.3/octave/defun-dld.h:30,
from /usr/include/octave-4.0.3/octave/oct.h:36,
from simppenadj.cpp:8:
/usr/include/octave-4.0.3/octave/ov.h:356:17: note: candidate: octave_value& octave_value::operator=(const octave_value&)
octave_value& operator = (const octave_value& a)
^~~~~~~~
/usr/include/octave-4.0.3/octave/ov.h:356:17: note: no known conversion for argument 1 from ‘std::vector<double>’ to ‘const octave_value&’
simppenadj.cpp:99:12: error: no match for ‘operator=’ (operand types are ‘octave_value’ and ‘std::vector<double>’)
in(2) = dx;
^~
In file included from /usr/include/octave-4.0.3/octave/oct-obj.h:33:0,
from /usr/include/octave-4.0.3/octave/ov-fcn.h:31,
from /usr/include/octave-4.0.3/octave/ov-builtin.h:28,
from /usr/include/octave-4.0.3/octave/defun-int.h:28,
from /usr/include/octave-4.0.3/octave/defun-dld.h:30,
from /usr/include/octave-4.0.3/octave/oct.h:36,
from simppenadj.cpp:8:
/usr/include/octave-4.0.3/octave/ov.h:356:17: note: candidate: octave_value& octave_value::operator=(const octave_value&)
octave_value& operator = (const octave_value& a)
^~~~~~~~
/usr/include/octave-4.0.3/octave/ov.h:356:17: note: no known conversion for argument 1 from ‘std::vector<double>’ to ‘const octave_value&’
make: *** [Makefile:3: all] Error 1
退回 . 显然， std::vector<double> 输入存在一些输入问题 . 所以问题是，"How does one pass vectors from C++ programs to GNU Octave functions called in said programs?"
1 回答
我通过一个小循环这样做：
如果你想从skript中获取数据，你必须在
outMatrix_y.length()上进行iterize .