Using Microsoft Solver Foundation, I have only solved linear problem so far. I'm now trying to solve a very simple non-linear problem but for some reasons, Microsoft solver cannot solve it.
The problem is maximising a0*a1 , with a0<10 and a1<20 .
Here is the code I'm using:
using System;
using Microsoft.SolverFoundation.Services;
namespace SolverFoundationDemo
{
class Program
{
static void Main(string[] args)
{
Console.WriteLine("\nBegin Solver demo\n");
var solver = SolverContext.GetContext();
var model = solver.CreateModel();
var decision1 = new Decision(Domain.RealNonnegative, "a0"); model.AddDecision(decision1);
var decision2 = new Decision(Domain.RealNonnegative, "a1"); model.AddDecision(decision2);
model.AddConstraint("Constraint0", "a0 <=10");
model.AddConstraint("Constraint1", "a1 <=20");
model.AddGoal("Goal", GoalKind.Maximize, " a0*a1 ");
var solution = solver.Solve();
Console.WriteLine("\nEnd Solver demo\n");
Console.ReadLine();
}
}
}
The error I get is " The model is not convex" , which is true but I was expecting Microsoft solver to be smart enough to find a solution anyway.
Thanks a lot for your feedback.
Regards,
Actually, Microsoft Solver choose NLP by default. For some reasons, if I add a useless constraint like a0*a1 < 1000000, it works. If I don't add this constraint, it does not work..
I'm really not satisfied with this Solver. Erwin, could you please tell me which solver should I use If I want to switch from Microsoft solver?
My program is written is C#. I have all my decisions and constraints inside Datable, and I pass it to the solver like shown below. In order to avoid to re-write the whole stuff, I would like a solver that I can feed using the same method..
string Comment = Convert.ToString(Table_Constraints.Rows[i]["Comment"]);
string Constraints = Convert.ToString(Table_Constraints.Rows[i]["Constraint"]);
model.AddConstraint(Comment, Constraints);
Related
When making the file, I am thinking of selecting a console application. But which target framework do I choose? Is this incorrect? Also, I am having trouble figuring out how to make a method in the class Program that is able to be called in the Main method. Can someone give me some advice?
one thing you can do is using interface to keep your code clean; for example :
you create an interface like this:
public interface IQuestionSolving
{
public void Solution();
}
you create some question class :
public class Question1 : IQuestionSolving
{
public void Solution()
{
}
}
and you use it like this :
static void Main(string[] args)
{
IQuestionSolving solve = new Question1();
solve.Solution();
Console.ReadKey();
}
now each time you solve a question you need to change
IQuestionSolving solve = new Question1();
to
IQuestionSolving solve = new Question2(); // 2 3 4 .. etc
you can extract your project as template so you dont have to do this each time .
or you can just use one solution and many classes .
This will get you started with Visual Studio:
Create a new console project - use the latest version of C#, which is probably what VS will "suggest" to you. Currently that's .NET 6 or .NET 7
A modern (net 6 or later) console app lets you start writing code immediately. You could create a method and then call the method right in this little Program.cs file that you start out with. However, I would probably do the following instead:
a) Create a new class for your "problem"
b) In that class create a method that solves the problem.
c) In your Program.cs add a using statement to use the namespace that your new class uses
d) In your program.cs instantiate that class and call its method/test its method
Here is an example:
Program.cs
using LeetCodeProject;
var solver = new Problem001_CalculateSquareRoot();
var solution = solver.calculate_square_root(8);
Console.WriteLine(solution);
Console.WriteLine("Press any key...");
Console.ReadKey();
Problem001_CalculateSquareRoot.cs (solves one leetcode problem)
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace LeetCodeProject
{
public class Problem001_CalculateSquareRoot
{
public double calculate_square_root(int number)
{
double root = 1;
int i = 0;
while (true)
{
i = i + 1;
root = (number / root + root) / 2;
if (i == number + 1)
{
break;
}
}
return root;
}
}
}
Now you can just add new classes for each problem, and as you work on them just edit Program.cs to create the class you are currently working with and calls its solution methods.
I can (and would - and actually have, in similar cases) implement an interface for this, but the goal here is not to get into OO design principles, but just to get you started so you can get to work on the leetcode problems...once you have a few done you can start thinking about better organization of the code.
I am trying to interface C# to R using RDotNet.
The following code is wants R to calculate the sum of two numbers and C# to get the result back and display it in the command window.
using System;
using RDotNet;
namespace rcon
{
class Program
{
static void Main(string[] args)
{
string dllPath = #"C:\Program Files\R\R-3.1.0\bin\i386";
REngine.SetDllDirectory(dllPath);
REngine.CreateInstance("RDotNet");
//REngine engine = REngine.GetInstanceFromID("RDotNet");
using (REngine engine = REngine.GetInstanceFromID("RDotNet"))
{
var x = engine.Evaluate("x <- 1 + 2");
Console.WriteLine(x);
}
}
}
}
but when I try to send the command to R and get back the calue in x I got an error:
"InvalidOperationException was unhandled"
"Operation is not valid due to the current state of the object."
If I explore the object "engine" I see that IsRunning=false.
Can this be the problem? And how can I fix this in order to be able to interface to R?
It looks like you have outdated version of R.NET.
From R.NET project documentation
R.NET 1.5.10 and subsequent versions include significant changes
notably to alleviate two stumbling blocks often dealt with by users:
paths to the R shared library, and preventing multiple engine
initializations.
You can update your R.NET using NuGet manager from Visual Studio. See the same documentation page for detals.
Here is code sample from the same documentatin page - note that initialization of REngine is significantly simpler now (as now Rengine looks at the Registry settings set up by the R installer):
REngine.SetEnvironmentVariables(); // <-- May be omitted; the next line would call it.
REngine engine = REngine.GetInstance();
// A somewhat contrived but customary Hello World:
CharacterVector charVec = engine.CreateCharacterVector(new[] { "Hello, R world!, .NET speaking" });
engine.SetSymbol("greetings", charVec);
engine.Evaluate("str(greetings)"); // print out in the console
string[] a = engine.Evaluate("'Hi there .NET, from the R engine'").AsCharacter().ToArray();
Console.WriteLine("R answered: '{0}'", a[0]);
Console.WriteLine("Press any key to exit the program");
Console.ReadKey();
engine.Dispose();
I'm trying to write some code to find all method invocations of any given method as I am looking to create an open source UML Sequence Diagramming tool. I'm having trouble, however, getting past the first few lines of code :/
The API appears to have changed drastically and I can't seem to infer proper usage by looking at the code.
When I do:
var workspace = new CustomWorkspace();
string solutionPath = #"C:\Workspace\RoslynTest\RoslynTest.sln";
var solution = workspace.CurrentSolution;
I find that workspace.CurrentSolution has 0 Projects. I figured this would be the equivalent to what was previously Workspace.LoadSolution( string solutionFile ) which would then supposedly contain any Projects in the Solution, but I am not finding any success with this path.
I am terribly confused 0.o
If someone could offer some additional guidance as to how I can use the FindReferences API to identify all invocations of a particular method, it would be very much appreciated!
Alternatively, would I be better off taking a static-analysis approach? I would like to support things like lambdas, iterator methods and async.
====================================================================
Edit -
Here is a full example based on the accepted answer:
using System.Linq;
using Microsoft.CodeAnalysis.CSharp;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.MSBuild;
using Microsoft.CodeAnalysis.FindSymbols;
using System.Diagnostics;
namespace RoslynTest
{
class Program
{
static void Main(string[] args)
{
string solutionPath = #"C:\Workspace\RoslynTest\RoslynTest.sln";
var workspace = MSBuildWorkspace.Create();
var solution = workspace.OpenSolutionAsync(solutionPath).Result;
var project = solution.Projects.Where(p => p.Name == "RoslynTest").First();
var compilation = project.GetCompilationAsync().Result;
var programClass = compilation.GetTypeByMetadataName("RoslynTest.Program");
var barMethod = programClass.GetMembers("Bar").First();
var fooMethod = programClass.GetMembers("Foo").First();
var barResult = SymbolFinder.FindReferencesAsync(barMethod, solution).Result.ToList();
var fooResult = SymbolFinder.FindReferencesAsync(fooMethod, solution).Result.ToList();
Debug.Assert(barResult.First().Locations.Count() == 1);
Debug.Assert(fooResult.First().Locations.Count() == 0);
}
public bool Foo()
{
return "Bar" == Bar();
}
public string Bar()
{
return "Bar";
}
}
}
CustomWorkspace is
A workspace that allows manual addition of projects and documents.
Since you're trying to load a solution, you should use the MSBuildWorkspace, which is
A workspace that can be populated by opening MSBuild solution and project files.
You can create a new MSBuildWorkspace and call OpenSolutionAsync with your solutionPath. For the reference finding part, take a look at the SymbolFinder.
Solutions are an MSBuild concept.
You need to create an MSBuildWorkspace and call OpenSolutionAsync().
string solutionPath = #"C:\Workspace\RoslynTest\RoslynTest.sln";
creates a local variable. It has no influence on your CustomWorkspace object.
I would like to do the equivalent of:
object result = Eval("1 + 3");
string now = Eval("System.DateTime.Now().ToString()") as string
Following Biri s link, I got this snippet (modified to remove obsolete method ICodeCompiler.CreateCompiler():
private object Eval(string sExpression)
{
CSharpCodeProvider c = new CSharpCodeProvider();
CompilerParameters cp = new CompilerParameters();
cp.ReferencedAssemblies.Add("system.dll");
cp.CompilerOptions = "/t:library";
cp.GenerateInMemory = true;
StringBuilder sb = new StringBuilder("");
sb.Append("using System;\n");
sb.Append("namespace CSCodeEvaler{ \n");
sb.Append("public class CSCodeEvaler{ \n");
sb.Append("public object EvalCode(){\n");
sb.Append("return " + sExpression + "; \n");
sb.Append("} \n");
sb.Append("} \n");
sb.Append("}\n");
CompilerResults cr = c.CompileAssemblyFromSource(cp, sb.ToString());
if (cr.Errors.Count > 0)
{
throw new InvalidExpressionException(
string.Format("Error ({0}) evaluating: {1}",
cr.Errors[0].ErrorText, sExpression));
}
System.Reflection.Assembly a = cr.CompiledAssembly;
object o = a.CreateInstance("CSCodeEvaler.CSCodeEvaler");
Type t = o.GetType();
MethodInfo mi = t.GetMethod("EvalCode");
object s = mi.Invoke(o, null);
return s;
}
Old topic, but considering this is one of the first threads showing up when googling, here is an updated solution.
You can use Roslyn's new Scripting API to evaluate expressions.
If you are using NuGet, just add a dependency to Microsoft.CodeAnalysis.CSharp.Scripting.
To evaluate the examples you provided, it is as simple as:
var result = CSharpScript.EvaluateAsync("1 + 3").Result;
This obviously does not make use of the scripting engine's async capabilities.
You can also specify the evaluated result type as you intended:
var now = CSharpScript.EvaluateAsync<string>("System.DateTime.Now.ToString()").Result;
To evaluate more advanced code snippets, pass parameters, provide references, namespaces and whatnot, check the wiki linked above.
I have written an open source project, Dynamic Expresso, that can convert text expression written using a C# syntax into delegates (or expression tree). Text expressions are parsed and transformed into Expression Trees without using compilation or reflection.
You can write something like:
var interpreter = new Interpreter();
var result = interpreter.Eval("8 / 2 + 2");
or
var interpreter = new Interpreter()
.SetVariable("service", new ServiceExample());
string expression = "x > 4 ? service.aMethod() : service.AnotherMethod()";
Lambda parsedExpression = interpreter.Parse(expression,
new Parameter("x", typeof(int)));
parsedExpression.Invoke(5);
My work is based on Scott Gu article http://weblogs.asp.net/scottgu/archive/2008/01/07/dynamic-linq-part-1-using-the-linq-dynamic-query-library.aspx .
If you specifically want to call into code and assemblies in your own project I would advocate using the C# CodeDom CodeProvider.
Here is a list of the most popular approaches that I am aware of for evaluating string expressions dynamically in C#.
Microsoft Solutions
C# CodeDom CodeProvider:
See How LINQ used to work and this CodeProject article
Roslyn:
See this article on Rosly Emit API and this StackOverflow answer
DataTable.Compute:
See this answer on StackOverflow
Webbrowser.Document.InvokeScript
See this StackOverflow question
DataBinder.Eval
ScriptControl
See this answer on StackOverflow and this question
Executing PowerShell:
See this CodeProject article
Non-Microsoft solutions (not that there is anything wrong with that)
Expression evaluation libraries:
Flee
DynamicExpresso
NCalc
CodingSeb.ExpressionEvaluator
Eval-Expression.NET
Javascript interpreter
Jint
To execute real C#
CS-Script
Roll your own a language building toolkit like:
Irony
Jigsaw
using System;
using Microsoft.JScript;
using Microsoft.JScript.Vsa;
using Convert = Microsoft.JScript.Convert;
namespace System
{
public class MathEvaluator : INeedEngine
{
private VsaEngine vsaEngine;
public virtual String Evaluate(string expr)
{
var engine = (INeedEngine)this;
var result = Eval.JScriptEvaluate(expr, engine.GetEngine());
return Convert.ToString(result, true);
}
VsaEngine INeedEngine.GetEngine()
{
vsaEngine = vsaEngine ?? VsaEngine.CreateEngineWithType(this.GetType().TypeHandle);
return vsaEngine;
}
void INeedEngine.SetEngine(VsaEngine engine)
{
vsaEngine = engine;
}
}
}
What are the performance implications of doing this?
We use a system based on something like the above mentioned, where each C# script is compiled to an in-memory assembly and executed in a separate AppDomain. There's no caching system yet, so the scripts are recompiled every time they run. I've done some simple testing and a very simple "Hello World" script compiles in about 0.7 seconds on my machine, including loading the script from disk. 0.7 seconds is fine for a scripting system, but might be too slow for responding to user input, in that case a dedicated parser/compiler like Flee might be better.
using System;
public class Test
{
static public void DoStuff( Scripting.IJob Job)
{
Console.WriteLine( "Heps" );
}
}
I have just written a similar library (Matheval) in pure C#.
It allows evaluating string and number expression like excel fomular.
using System;
using org.matheval;
public class Program
{
public static void Main()
{
Expression expression = new Expression("IF(time>8, (HOUR_SALARY*8) + (HOUR_SALARY*1.25*(time-8)), HOUR_SALARY*time)");
//bind variable
expression.Bind("HOUR_SALARY", 10);
expression.Bind("time", 9);
//eval
Decimal salary = expression.Eval<Decimal>();
Console.WriteLine(salary);
}
}
Looks like there is also a way of doing it using RegEx and XPathNavigator to evaluate the expression. I did not have the chance to test it yet but I kind of liked it because it did not require to compile code at runtime or use libraries that could not be available.
http://www.webtips.co.in/c/evaluate-function-in-c-net-as-eval-function-in-javascript.aspx
I'll try it and tell later if it worked. I also intend to try it in Silverlight, but it is too late and I'm almost asleep to do it now.
While C# doesn't have any support for an Eval method natively, I have a C# eval program that does allow for evaluating C# code. It provides for evaluating C# code at runtime and supports many C# statements. In fact, this code is usable within any .NET project, however, it is limited to using C# syntax. Have a look at my website, http://csharp-eval.com, for additional details.
There is a nice piece of code here
https://www.c-sharpcorner.com/article/codedom-calculator-evaluating-c-sharp-math-expressions-dynamica/
Download this and make it a class library which may be referenced in your project. This seems to be pretty fast and simple
Perhaps this could help !
I would like to do the equivalent of:
object result = Eval("1 + 3");
string now = Eval("System.DateTime.Now().ToString()") as string
Following Biri s link, I got this snippet (modified to remove obsolete method ICodeCompiler.CreateCompiler():
private object Eval(string sExpression)
{
CSharpCodeProvider c = new CSharpCodeProvider();
CompilerParameters cp = new CompilerParameters();
cp.ReferencedAssemblies.Add("system.dll");
cp.CompilerOptions = "/t:library";
cp.GenerateInMemory = true;
StringBuilder sb = new StringBuilder("");
sb.Append("using System;\n");
sb.Append("namespace CSCodeEvaler{ \n");
sb.Append("public class CSCodeEvaler{ \n");
sb.Append("public object EvalCode(){\n");
sb.Append("return " + sExpression + "; \n");
sb.Append("} \n");
sb.Append("} \n");
sb.Append("}\n");
CompilerResults cr = c.CompileAssemblyFromSource(cp, sb.ToString());
if (cr.Errors.Count > 0)
{
throw new InvalidExpressionException(
string.Format("Error ({0}) evaluating: {1}",
cr.Errors[0].ErrorText, sExpression));
}
System.Reflection.Assembly a = cr.CompiledAssembly;
object o = a.CreateInstance("CSCodeEvaler.CSCodeEvaler");
Type t = o.GetType();
MethodInfo mi = t.GetMethod("EvalCode");
object s = mi.Invoke(o, null);
return s;
}
Old topic, but considering this is one of the first threads showing up when googling, here is an updated solution.
You can use Roslyn's new Scripting API to evaluate expressions.
If you are using NuGet, just add a dependency to Microsoft.CodeAnalysis.CSharp.Scripting.
To evaluate the examples you provided, it is as simple as:
var result = CSharpScript.EvaluateAsync("1 + 3").Result;
This obviously does not make use of the scripting engine's async capabilities.
You can also specify the evaluated result type as you intended:
var now = CSharpScript.EvaluateAsync<string>("System.DateTime.Now.ToString()").Result;
To evaluate more advanced code snippets, pass parameters, provide references, namespaces and whatnot, check the wiki linked above.
I have written an open source project, Dynamic Expresso, that can convert text expression written using a C# syntax into delegates (or expression tree). Text expressions are parsed and transformed into Expression Trees without using compilation or reflection.
You can write something like:
var interpreter = new Interpreter();
var result = interpreter.Eval("8 / 2 + 2");
or
var interpreter = new Interpreter()
.SetVariable("service", new ServiceExample());
string expression = "x > 4 ? service.aMethod() : service.AnotherMethod()";
Lambda parsedExpression = interpreter.Parse(expression,
new Parameter("x", typeof(int)));
parsedExpression.Invoke(5);
My work is based on Scott Gu article http://weblogs.asp.net/scottgu/archive/2008/01/07/dynamic-linq-part-1-using-the-linq-dynamic-query-library.aspx .
If you specifically want to call into code and assemblies in your own project I would advocate using the C# CodeDom CodeProvider.
Here is a list of the most popular approaches that I am aware of for evaluating string expressions dynamically in C#.
Microsoft Solutions
C# CodeDom CodeProvider:
See How LINQ used to work and this CodeProject article
Roslyn:
See this article on Rosly Emit API and this StackOverflow answer
DataTable.Compute:
See this answer on StackOverflow
Webbrowser.Document.InvokeScript
See this StackOverflow question
DataBinder.Eval
ScriptControl
See this answer on StackOverflow and this question
Executing PowerShell:
See this CodeProject article
Non-Microsoft solutions (not that there is anything wrong with that)
Expression evaluation libraries:
Flee
DynamicExpresso
NCalc
CodingSeb.ExpressionEvaluator
Eval-Expression.NET
Javascript interpreter
Jint
To execute real C#
CS-Script
Roll your own a language building toolkit like:
Irony
Jigsaw
using System;
using Microsoft.JScript;
using Microsoft.JScript.Vsa;
using Convert = Microsoft.JScript.Convert;
namespace System
{
public class MathEvaluator : INeedEngine
{
private VsaEngine vsaEngine;
public virtual String Evaluate(string expr)
{
var engine = (INeedEngine)this;
var result = Eval.JScriptEvaluate(expr, engine.GetEngine());
return Convert.ToString(result, true);
}
VsaEngine INeedEngine.GetEngine()
{
vsaEngine = vsaEngine ?? VsaEngine.CreateEngineWithType(this.GetType().TypeHandle);
return vsaEngine;
}
void INeedEngine.SetEngine(VsaEngine engine)
{
vsaEngine = engine;
}
}
}
What are the performance implications of doing this?
We use a system based on something like the above mentioned, where each C# script is compiled to an in-memory assembly and executed in a separate AppDomain. There's no caching system yet, so the scripts are recompiled every time they run. I've done some simple testing and a very simple "Hello World" script compiles in about 0.7 seconds on my machine, including loading the script from disk. 0.7 seconds is fine for a scripting system, but might be too slow for responding to user input, in that case a dedicated parser/compiler like Flee might be better.
using System;
public class Test
{
static public void DoStuff( Scripting.IJob Job)
{
Console.WriteLine( "Heps" );
}
}
I have just written a similar library (Matheval) in pure C#.
It allows evaluating string and number expression like excel fomular.
using System;
using org.matheval;
public class Program
{
public static void Main()
{
Expression expression = new Expression("IF(time>8, (HOUR_SALARY*8) + (HOUR_SALARY*1.25*(time-8)), HOUR_SALARY*time)");
//bind variable
expression.Bind("HOUR_SALARY", 10);
expression.Bind("time", 9);
//eval
Decimal salary = expression.Eval<Decimal>();
Console.WriteLine(salary);
}
}
Looks like there is also a way of doing it using RegEx and XPathNavigator to evaluate the expression. I did not have the chance to test it yet but I kind of liked it because it did not require to compile code at runtime or use libraries that could not be available.
http://www.webtips.co.in/c/evaluate-function-in-c-net-as-eval-function-in-javascript.aspx
I'll try it and tell later if it worked. I also intend to try it in Silverlight, but it is too late and I'm almost asleep to do it now.
While C# doesn't have any support for an Eval method natively, I have a C# eval program that does allow for evaluating C# code. It provides for evaluating C# code at runtime and supports many C# statements. In fact, this code is usable within any .NET project, however, it is limited to using C# syntax. Have a look at my website, http://csharp-eval.com, for additional details.
There is a nice piece of code here
https://www.c-sharpcorner.com/article/codedom-calculator-evaluating-c-sharp-math-expressions-dynamica/
Download this and make it a class library which may be referenced in your project. This seems to be pretty fast and simple
Perhaps this could help !