Bugging esmpy 7.1.0.dev35

ESMPy_writeweights_debug.ipynb

{
 "cells": [
  {
   "cell_type": "code",
   "execution_count": 1,
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   "source": [
    "# Switch to Python 3 syntax because we are using Python2.7\n",
    "# from https://hub.docker.com/r/continuumio/miniconda/\n",
    "from __future__ import (absolute_import, division,\n",
    "                        print_function, unicode_literals)\n",
    "\n",
    "import numpy as np\n",
    "import xarray as xr\n",
    "import ESMF"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "ESMPyManager:\n",
       "    local_pet = 0\n",
       "    pet_count = 1\n",
       ")"
      ]
     },
     "execution_count": 2,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "ESMF.Manager(debug=True)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Create source and destination grids"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "The source grid has 20x20 = 400 grid cells and the destination grid has 10x10 = 100 grid cells. They cover the same spatial domain."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "sourcegrid = ESMF.Grid(np.array([20,20]), \n",
    "                       staggerloc = ESMF.StaggerLoc.CENTER,\n",
    "                       coord_sys = ESMF.CoordSys.SPH_DEG)\n",
    "\n",
    "source_lon = sourcegrid.get_coords(0)\n",
    "source_lat = sourcegrid.get_coords(1)\n",
    "source_lon[...], source_lat[...] = np.meshgrid(np.linspace(-120, 120, 20), \n",
    "                                               np.linspace(-60, 60, 20))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "destgrid = ESMF.Grid(np.array([10,10]), \n",
    "                     staggerloc = ESMF.StaggerLoc.CENTER,\n",
    "                     coord_sys = ESMF.CoordSys.SPH_DEG)\n",
    "\n",
    "dest_lon = destgrid.get_coords(0)\n",
    "dest_lat = destgrid.get_coords(1)\n",
    "dest_lon[...], dest_lat[...] = np.meshgrid(np.linspace(-120, 120, 10),\n",
    "                                           np.linspace(-60, 60, 10))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "sourcefield = ESMF.Field(sourcegrid)\n",
    "destfield = ESMF.Field(destgrid)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Write offline regridding weights"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {
    "scrolled": true
   },
   "outputs": [],
   "source": [
    "regrid_offline = ESMF.Regrid(sourcefield, destfield, filename='weights.nc',\n",
    "                        regrid_method = ESMF.RegridMethod.BILINEAR,\n",
    "                        unmapped_action = ESMF.UnmappedAction.IGNORE)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Open the weight file"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "<xarray.Dataset>\n",
       "Dimensions:  (n_s: 400)\n",
       "Dimensions without coordinates: n_s\n",
       "Data variables:\n",
       "    S        (n_s) float64 1.0 0.0 0.0 0.0 0.8887 0.1113 -3.947e-16 ...\n",
       "    col      (n_s) int32 1 1 2 1 21 1 22 1 3 2 4 2 23 2 24 2 5 3 6 3 25 3 26 ...\n",
       "    row      (n_s) int32 1 2 1 21 1 22 1 3 2 4 2 23 2 24 2 5 3 6 3 25 3 26 3 ..."
      ]
     },
     "execution_count": 7,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "ds = xr.open_dataset('weights.nc')\n",
    "ds"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "According to ESMF documentation [12.7.3 Regrid Calculation Output](http://www.earthsystemmodeling.org/esmf_releases/last_built/ESMF_refdoc/node3.html#SECTION03027300000000000000), the variable meanings are\n",
    "\n",
    "    n_s: The number of entries in the regridding matrix.\n",
    "    col: The position in the source grid for each entry in the regridding matrix.\n",
    "    row: The position in the destination grid for each entry in the weight matrix.\n",
    "    S: The weight for each entry in the regridding matrix."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "The Fortran code for applying weights is\n",
    "\n",
    "     ! Apply weights\n",
    "     do i=1, n_s\n",
    "       dst_field(row(i))=dst_field(row(i))+S(i)*src_field(col(i))\n",
    "     enddo"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "This means, the variable `col` should take integers from 1 to the number of grid boxes in the source grid (400 here), and the variable `row` should take integers from 1 to the destination grid number (100 here). \n",
    "\n",
    "**However, the ranges of `col` and `row` are wrong:**"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "col = ds['col'].values\n",
    "row = ds['row'].values"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "(1, 200)"
      ]
     },
     "execution_count": 9,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "col.min(), col.max() # should have been 1~400"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "(1, 201)"
      ]
     },
     "execution_count": 10,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "row.min(), row.max() # should have been 1~100"
   ]
  }
 ],
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