Dear all,

I tried to run the example in p. 401 of the NR book but it gives some errors. Here is my source code:

#include "C:\Program Files\Numerical Recipes\NR_C302\code\nr3.h"
#include "C:\Program Files\Numerical Recipes\NR_C302\code/mcintegrate.h"
#include "C:\Program Files\Numerical Recipes\NR_C302\code/ran.h"
//
// Driver for routine Mcintegration
// Extracted by Amir Vahid from sec. 7.7
//

int main()
{
VecDoub xlo(3), xhi(3);
xlo[0] = 1.; xhi[0] = 4.;
xlo[1] = -3.; xhi[1] = 4.;
xlo[2] = -1.; xhi[2] = 1.;
MCintegrate mymc(xlo,xhi,torusfuncs,torusregion,NULL,10201);
mymc.step(1000000);
mymc.calcanswers();
return 0;
}

VecDoub torusfuncs(const VecDoub &x) {
//Return the integrands in equation (7.7.5), with . rho=1.
Doub den = 1.;
VecDoub f(4);
f[0] = den;
for (Int i=1;i<4;i++) f[i] = x[i-1]*den;
return f;
}

Bool torusregion(const VecDoub &x) {
//Return the inequality (7.7.3).
return SQR(x[2])+SQR(sqrt(SQR(x[0])+SQR(x[1]))-3.) <= 1.;
}

Here are the listed errors.

1>------ Rebuild All started: Project: McIntegrate, Configuration: Debug Win32 ------
1>Deleting intermediate and output files for project 'McIntegrate', configuration 'Debug|Win32'
1>Compiling...
1>McIntegrate.cpp
1>c:\program files\numerical recipes\nr_c302\code\mcintegrate.h(10) : error C2146: syntax error : missing ';' before identifier 'ran'
1>c:\program files\numerical recipes\nr_c302\code\mcintegrate.h(10) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
1>c:\program files\numerical recipes\nr_c302\code\mcintegrate.h(10) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
1>c:\program files\numerical recipes\nr_c302\code\mcintegrate.h(24) : error C2614: 'MCintegrate' : illegal member initialization: 'ran' is not a base or member
1>c:\program files\numerical recipes\nr_c302\code\mcintegrate.h(39) : error C2065: 'ran' : undeclared identifier
1>c:\program files\numerical recipes\nr_c302\code\mcintegrate.h(39) : error C2228: left of '.doub' must have class/struct/union
1> type is ''unknown-type''
1>c:\my projects\mcintegrate\mcintegrate\mcintegrate.cpp(2 1) : error C2084: function 'VecDoub torusfuncs(const VecDoub &)' already has a body
1> c:\program files\numerical recipes\nr_c302\code\mcintegrate.h(59) : see previous definition of 'torusfuncs'
1>c:\my projects\mcintegrate\mcintegrate\mcintegrate.cpp(3 0) : error C2084: function 'Bool torusregion(const VecDoub &)' already has a body
1> c:\program files\numerical recipes\nr_c302\code\mcintegrate.h(67) : see previous definition of 'torusregion'
1>Build log was saved at "file://c:\My Projects\McIntegrate\McIntegrate\Debug\BuildLog.ht m"
1>McIntegrate - 8 error(s), 0 warning(s)
========== Rebuild All: 0 succeeded, 1 failed, 0 skipped ==========


I wonder if you could help me fix this problem. Thanks

Have you tried fixing the first bug?

1>c:\program files\numerical recipes\nr_c302\code\mcintegrate.h(10) : error C2146: syntax error : missing ';' before identifier 'ran'


Simply states that you are missing a semicolon.

Fix that simple bug and then try to compile.

Let us know if that works.

Thanks
Matt

...it gives some errors...

1. You must include ran.h before you include mcintegrate.h See the master dependencies list (http://www.nr.com/dependencies/masterdependency.txt)

2. Since the functions torusfuncs() and torusregion() are implemented in mcintegrate.h you should not put them in your main program file.

Regards,

Dave

Have you tried fixing the first bug?



Simply states that you are missing a semicolon.

Fix that simple bug and then try to compile.

Let us know if that works.

Thanks
Matt

Matt, thanks but I think this was not the issue.

Thanks Dave for your help. The code is running now. The above-mentioned function are actually implemented in the "mcintegrate.h" header file. I appreciate it! Here is the working code:

##include "C:\Program Files\Numerical Recipes\NR_C302\code\nr3.h"
#include "C:\Program Files\Numerical Recipes\NR_C302\code/ran.h"
#include "C:\Program Files\Numerical Recipes\NR_C302\code/mcintegrate.h"

//
// Driver for routine Mcintegration
// Extracted by Amir Vahid from Sec. 7.7.
//

int main()
{
VecDoub xlo(3), xhi(3);
xlo[0] = 1.; xhi[0] = 4.;
xlo[1] = -3.; xhi[1] = 4.;
xlo[2] = -1.; xhi[2] = 1.;
MCintegrate mymc(xlo,xhi,torusfuncs,torusregion,NULL,10201);
mymc.step(1000000);
mymc.calcanswers();
for (Int i=1;i<4;i++){
cout << mymc.ff[i] << endl;
}
return 0;
}


}

...include ran.h before you include mcintegrate.h

Ahh, yes. I overlooked that. I have done that before. :)

Glad it all works correctly for you now.

Thanks
Matt

Dear All,
The code that I have posted is for a volume in a cube which its equation (or constraints) is known. But suppose that we have a volume with an unknown equation. A general method for calculating of its volume is putting the volume in a cube and assigning meshes to it. This method is not efficient , however. Do you think that there is a way of doing that with Monte Carlo integration? Is it mentioned in Chapter 7? Thanks