implement sub-interpreters

CMakeLists.txt

@@ -189,6 +189,7 @@ set(XEUS_CPP_SRC
     src/xparser.cpp
     src/xutils.cpp
     src/xmagics/os.cpp
+    src/xmagics/multi_interpreter.cpp
 )
 
 if(NOT EMSCRIPTEN)

notebooks/sub-interpreters.ipynb

@@ -0,0 +1,216 @@
+{
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "id": "fb74181a-b881-4ae9-9224-495425707762",
+   "metadata": {},
+   "source": [
+    "**Default Interpreter of the Kernel**"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 1,
+   "id": "e5375e1a-347b-461e-97ac-1a5bc708c896",
+   "metadata": {
+    "vscode": {
+     "languageId": "c++"
+    }
+   },
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "201703\n"
+     ]
+    }
+   ],
+   "source": [
+    "#include <iostream>\n",
+    "std::cout << __cplusplus << std::endl;"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "7ec1684f-ce9a-4614-8f7c-8391b68f7eb5",
+   "metadata": {},
+   "source": [
+    "**Creating New Sub-Interpreter with `-std=c++23`**\n",
+    "\n",
+    "_We give it a name `cpp23` to re-use later_"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 2,
+   "id": "756696a7-c8db-4302-8794-029664673952",
+   "metadata": {
+    "vscode": {
+     "languageId": "c++"
+    }
+   },
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Elapsed time (C++23): 5.97e-06 seconds\n"
+     ]
+    }
+   ],
+   "source": [
+    "%%subinterp -Wall -O3 --std=c++23 --name cpp23\n",
+    "\n",
+    "#include <iostream>\n",
+    "#include <vector>\n",
+    "#include <ranges>\n",
+    "#include <chrono>\n",
+    "\n",
+    "void version() { std::cout << __cplusplus << std::endl; }\n",
+    "\n",
+    "template <std::ranges::range R> constexpr auto to_vector(R&& r) { return std::vector<std::decay_t<std::ranges::range_value_t<R>>>{r.begin(), r.end()}; }\n",
+    "\n",
+    "void run() {\n",
+    "    std::vector<int> numbers(10'000);\n",
+    "    for (int i = 0; i < 10'000; i++) numbers.push_back(i);\n",
+    "    \n",
+    "    auto start = std::chrono::high_resolution_clock::now();\n",
+    "    std::vector<int> result = to_vector(\n",
+    "        numbers \n",
+    "            | std::views::filter([](int n) { return n % 2 != 0; })  // filter out even numbers\n",
+    "            | std::views::transform([](int n) { return n * 2; }));   // multiply remaining by 2\n",
+    "    auto end = std::chrono::high_resolution_clock::now();\n",
+    "    \n",
+    "    std::chrono::duration<double> elapsed = end - start;\n",
+    "    std::cout << \"Elapsed time (C++23): \" << elapsed.count() << \" seconds\\n\";\n",
+    "}\n",
+    "run();"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "1a31f103-b92a-44e9-bf42-61709340bdc4",
+   "metadata": {},
+   "source": [
+    "**Creating Another Sub-Interpreter with `-std=c++11`**"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 3,
+   "id": "4f3391f7-0a38-4cd9-af2b-33245a06db84",
+   "metadata": {
+    "vscode": {
+     "languageId": "c++"
+    }
+   },
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Elapsed time (C++11): 5.22e-06 seconds\n"
+     ]
+    }
+   ],
+   "source": [
+    "%%subinterp -O3 --std=c++11 --name cpp11\n",
+    "\n",
+    "#include <iostream>\n",
+    "#include <vector>\n",
+    "#include <algorithm>\n",
+    "#include <chrono>\n",
+    "\n",
+    "void version() { std::cout << __cplusplus << std::endl; }\n",
+    "\n",
+    "void run() {\n",
+    "    std::vector<int> numbers(10000);\n",
+    "    for (int i = 0; i < 10000; i++) numbers.push_back(i);\n",
+    "    std::vector<int> result;\n",
+    "\n",
+    "    auto start = std::chrono::high_resolution_clock::now();\n",
+    "    std::copy_if(numbers.begin(), numbers.end(), std::back_inserter(result),\n",
+    "        [](int n) { return n % 2 != 0; }); // filter out even numbers\n",
+    "    std::transform(result.begin(), result.end(), result.begin(),\n",
+    "        [](int n) { return n * 2; }); // multiply remaining by 2\n",
+    "    auto end = std::chrono::high_resolution_clock::now();\n",
+    "    \n",
+    "    std::chrono::duration<double> elapsed = end - start;\n",
+    "    std::cout << \"Elapsed time (C++11): \" << elapsed.count() << \" seconds\\n\";\n",
+    "}\n",
+    "run();"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "63cecedc-0e72-43fd-80e4-36a612a8042b",
+   "metadata": {},
+   "source": [
+    "**Re-Using the Interpreter Created Previously**"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 4,
+   "id": "600da197-f902-4cf4-a401-a848e08aa638",
+   "metadata": {
+    "vscode": {
+     "languageId": "c++"
+    }
+   },
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "202302\n"
+     ]
+    }
+   ],
+   "source": [
+    "%%subinterp --use cpp23\n",
+    "version();"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 5,
+   "id": "2c2fa915-a6de-4477-b4f8-6c342720c224",
+   "metadata": {
+    "vscode": {
+     "languageId": "c++"
+    }
+   },
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "201103\n"
+     ]
+    }
+   ],
+   "source": [
+    "%%subinterp --use cpp11\n",
+    "version();"
+   ]
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "C++17",
+   "language": "cpp",
+   "name": "xcpp17"
+  },
+  "language_info": {
+   "codemirror_mode": "text/x-c++src",
+   "file_extension": ".cpp",
+   "mimetype": "text/x-c++src",
+   "name": "C++",
+   "version": "17"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 5
+}

src/xinterpreter.cpp

@@ -25,6 +25,8 @@
 #include "xparser.hpp"
 #include "xsystem.hpp"
 
+#include "xmagics/multi_interpreter.hpp"
+
 using Args = std::vector<const char*>;
 
 void* createInterpreter(const Args &ExtraArgs = {}) {
@@ -371,6 +373,7 @@ __get_cxx_version ()
         // preamble_manager["magics"].get_cast<xmagics_manager>().register_magic("timeit",
         // timeit(&m_interpreter));
         // preamble_manager["magics"].get_cast<xmagics_manager>().register_magic("python", pythonexec());
+        preamble_manager["magics"].get_cast<xmagics_manager>().register_magic("subinterp", multi_interpreter());
         preamble_manager["magics"].get_cast<xmagics_manager>().register_magic("file", writefile());
 #ifndef EMSCRIPTEN
         preamble_manager["magics"].get_cast<xmagics_manager>().register_magic("xassist", xassist());

src/xmagics/multi_interpreter.cpp

@@ -0,0 +1,93 @@
+/************************************************************************************
+ * Copyright (c) 2025, xeus-cpp contributors                                        *
+ *                                                                                  *
+ * Distributed under the terms of the BSD 3-Clause License.                         *
+ *                                                                                  *
+ * The full license is in the file LICENSE, distributed with this software.         *
+ ************************************************************************************/
+
+#include "multi_interpreter.hpp"
+
+#include <iostream>
+#include <iterator>
+#include <sstream>
+#include <string>
+#include <vector>
+
+#include "CppInterOp/CppInterOp.h"
+
+static std::vector<std::string> split(const std::string& input)
+{
+    std::istringstream buffer(input);
+    std::vector<std::string> ret(
+        (std::istream_iterator<std::string>(buffer)),
+        std::istream_iterator<std::string>()
+    );
+    return ret;
+}
+
+static constexpr size_t len(std::string_view n)
+{
+    return n.size();
+}
+
+namespace xcpp
+{
+    void multi_interpreter::operator()(const std::string& line, const std::string& cell)
+    {
+        auto Args0 = split(line.substr(len("subinterp")));
+
+        Cpp::TInterp_t OldI = Cpp::GetInterpreter();  // we need to restore the old interpreter
+        Cpp::TInterp_t I = nullptr;
+        std::string name;
+        if (Args0[0] == "--use")
+        {
+            I = interpreters[Args0[1]];
+        }
+        else
+        {
+            auto named = std::find(Args0.begin(), Args0.end(), "--name");
+            if (named != Args0.end())
+            {
+                name = *(named + 1);
+            }
+        }
+
+        std::vector<const char*> Args(I ? 0 : Args0.size());
+        if (!I)
+        {
+            for (auto start = Args0.begin(), end = Args0.end(); start != end; start++)
+            {
+                if (*start == "--name")
+                {
+                    start++;
+                    continue;
+                }
+                Args.push_back((*start).c_str());
+            }
+        }
+
+        Cpp::BeginStdStreamCapture(Cpp::kStdErr);
+        Cpp::BeginStdStreamCapture(Cpp::kStdOut);
+        if (!I)
+        {
+            I = Cpp::CreateInterpreter(Args);  // TODO: error handling
+        }
+        if (I)
+        {
+            Cpp::Declare(cell.c_str(), false, I);
+        }
+        std::cout << Cpp::EndStdStreamCapture();
+        std::cerr << Cpp::EndStdStreamCapture();
+
+        if (!name.empty())
+        {
+            interpreters[name] = I;          // TODO: check if this is redefinition
+            Cpp::ActivateInterpreter(OldI);  // restoring old interpreter
+        }
+        else
+        {
+            Cpp::DeleteInterpreter(I);
+        }
+    }
+}  // namespace xcpp

src/xmagics/multi_interpreter.hpp

@@ -0,0 +1,33 @@
+/************************************************************************************
+ * Copyright (c) 2025, xeus-cpp contributors                                        *
+ *                                                                                  *
+ * Distributed under the terms of the BSD 3-Clause License.                         *
+ *                                                                                  *
+ * The full license is in the file LICENSE, distributed with this software.         *
+ ************************************************************************************/
+
+#ifndef XEUS_CPP_MULTI_INTERPRETER_MAGIC_HPP
+#define XEUS_CPP_MULTI_INTERPRETER_MAGIC_HPP
+
+#include <string>
+#include <unordered_map>
+
+#include "CppInterOp/CppInterOp.h"
+#include "xeus-cpp/xmagics.hpp"
+
+namespace xcpp
+{
+    class multi_interpreter : public xmagic_cell
+    {
+    public:
+
+        XEUS_CPP_API
+        void operator()(const std::string& line, const std::string& cell) override;
+
+    private:
+
+        std::unordered_map<std::string, Cpp::TInterp_t> interpreters;
+    };
+}  // namespace xcpp
+
+#endif  // XEUS_CPP_MULTI_INTERPRETER_MAGIC_HPP