{
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  {
   "cell_type": "markdown",
   "id": "e041e38a",
   "metadata": {},
   "source": [
    "# tmva001_RTensor\n",
    "This tutorial illustrates the basic features of the RTensor class,\n",
    "RTensor is a std::vector-like container with additional shape information.\n",
    "The class serves as an interface in C++ between multi-dimensional data and\n",
    "the algorithm such as in machine learning workflows. The interface is similar\n",
    "to Numpy arrays and provides a subset of the functionality.\n",
    "\n",
    "\n",
    "\n",
    "\n",
    "**Author:** Stefan Wunsch  \n",
    "<i><small>This notebook tutorial was automatically generated with <a href= \"https://github.com/root-project/root/blob/master/documentation/doxygen/converttonotebook.py\">ROOTBOOK-izer</a> from the macro found in the ROOT repository  on Tuesday, May 19, 2026 at 08:22 PM.</small></i>"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "id": "1079e162",
   "metadata": {
    "collapsed": false,
    "execution": {
     "iopub.execute_input": "2026-05-19T20:22:29.772749Z",
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     "shell.execute_reply": "2026-05-19T20:22:30.090468Z"
    }
   },
   "outputs": [],
   "source": [
    "using namespace TMVA::Experimental;"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "c5e4acd3",
   "metadata": {},
   "source": [
    "Create RTensor from scratch"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "id": "61b92bfe",
   "metadata": {
    "collapsed": false,
    "execution": {
     "iopub.execute_input": "2026-05-19T20:22:30.092663Z",
     "iopub.status.busy": "2026-05-19T20:22:30.092521Z",
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     "shell.execute_reply": "2026-05-19T20:22:30.299676Z"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "{ { 0, 0 } { 0, 0 } }\n"
     ]
    }
   ],
   "source": [
    "RTensor<float> x({2, 2});\n",
    "cout << x << endl;"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "06f73d19",
   "metadata": {},
   "source": [
    "Assign some data"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "id": "f18fa620",
   "metadata": {
    "collapsed": false,
    "execution": {
     "iopub.execute_input": "2026-05-19T20:22:30.301725Z",
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     "shell.execute_reply": "2026-05-19T20:22:30.506655Z"
    }
   },
   "outputs": [],
   "source": [
    "x(0, 0) = 1;\n",
    "x(0, 1) = 2;\n",
    "x(1, 0) = 3;\n",
    "x(1, 1) = 4;"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "d2bdc1f9",
   "metadata": {},
   "source": [
    "Apply transformations"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "id": "c61b00ff",
   "metadata": {
    "collapsed": false,
    "execution": {
     "iopub.execute_input": "2026-05-19T20:22:30.508837Z",
     "iopub.status.busy": "2026-05-19T20:22:30.508718Z",
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     "shell.execute_reply": "2026-05-19T20:22:30.729363Z"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "{ 1, 2, 3, 4 }\n"
     ]
    }
   ],
   "source": [
    "auto x2 = x.Reshape({1, 4}).Squeeze();\n",
    "cout << x2 << endl;"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "c50a1a3b",
   "metadata": {},
   "source": [
    "Slice"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "id": "298d09de",
   "metadata": {
    "collapsed": false,
    "execution": {
     "iopub.execute_input": "2026-05-19T20:22:30.732931Z",
     "iopub.status.busy": "2026-05-19T20:22:30.732818Z",
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     "shell.execute_reply": "2026-05-19T20:22:30.937766Z"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "{ 1, 3 }\n"
     ]
    }
   ],
   "source": [
    "auto x3 = x.Reshape({2, 2}).Slice({{0, 2}, {0, 1}});\n",
    "cout << x3 << endl;"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "1ff4caa9",
   "metadata": {},
   "source": [
    "Create tensor as view on data without ownership"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "id": "55c07411",
   "metadata": {
    "collapsed": false,
    "execution": {
     "iopub.execute_input": "2026-05-19T20:22:30.939273Z",
     "iopub.status.busy": "2026-05-19T20:22:30.939164Z",
     "iopub.status.idle": "2026-05-19T20:22:31.144791Z",
     "shell.execute_reply": "2026-05-19T20:22:31.144392Z"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "{ { 5, 6 } { 7, 8 } }\n"
     ]
    },
    {
     "name": "stderr",
     "output_type": "stream",
     "text": [
      "input_line_57:2:2: warning: 'data' shadows a declaration with the same name in the 'std' namespace; use '::data' to reference this declaration\n",
      " float data[] = {5, 6, 7, 8};\n",
      " ^\n"
     ]
    }
   ],
   "source": [
    "float data[] = {5, 6, 7, 8};\n",
    "RTensor<float> y(data, {2, 2});\n",
    "cout << y << endl;"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "2e9549e9",
   "metadata": {},
   "source": [
    "Create tensor as view on data with ownership"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "id": "eb8fb8b2",
   "metadata": {
    "collapsed": false,
    "execution": {
     "iopub.execute_input": "2026-05-19T20:22:31.145888Z",
     "iopub.status.busy": "2026-05-19T20:22:31.145782Z",
     "iopub.status.idle": "2026-05-19T20:22:31.351186Z",
     "shell.execute_reply": "2026-05-19T20:22:31.350815Z"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "{ { 9, 10 } { 11, 12 } }\n"
     ]
    }
   ],
   "source": [
    "auto data2 = std::make_shared<std::vector<float>>(4);\n",
    "float c = 9;\n",
    "for (auto &v : *data2) {\n",
    "   v = c;\n",
    "   c++;\n",
    "}\n",
    "\n",
    "RTensor<float> z(data2, {2, 2});\n",
    "cout << z << endl;"
   ]
  }
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