mathjs/lib/type/matrix/utils/algorithm05.js

Math.js is an extensive math library for JavaScript and Node.js. It features a flexible expression parser with support for symbolic computation, comes with a large set of built-in functions and constants, and offers an integrated solution to work with dif

'use strict';

var DimensionError = require('../../../error/DimensionError');

function factory(type, config, load, typed) {
  var equalScalar = load(require('../../../function/relational/equalScalar'));
  var SparseMatrix = type.SparseMatrix;
  /**
   * Iterates over SparseMatrix A and SparseMatrix B nonzero items and invokes the callback function f(Aij, Bij).
   * Callback function invoked MAX(NNZA, NNZB) times
   *
   *
   *          ┌  f(Aij, Bij)  ; A(i,j) !== 0 || B(i,j) !== 0
   * C(i,j) = ┤
   *          └  0            ; otherwise
   *
   *
   * @param {Matrix}   a                 The SparseMatrix instance (A)
   * @param {Matrix}   b                 The SparseMatrix instance (B)
   * @param {Function} callback          The f(Aij,Bij) operation to invoke
   *
   * @return {Matrix}                    SparseMatrix (C)
   *
   * see https://github.com/josdejong/mathjs/pull/346#issuecomment-97620294
   */

  var algorithm05 = function algorithm05(a, b, callback) {
    // sparse matrix arrays
    var avalues = a._values;
    var aindex = a._index;
    var aptr = a._ptr;
    var asize = a._size;
    var adt = a._datatype; // sparse matrix arrays

    var bvalues = b._values;
    var bindex = b._index;
    var bptr = b._ptr;
    var bsize = b._size;
    var bdt = b._datatype; // validate dimensions

    if (asize.length !== bsize.length) {
      throw new DimensionError(asize.length, bsize.length);
    } // check rows & columns


    if (asize[0] !== bsize[0] || asize[1] !== bsize[1]) {
      throw new RangeError('Dimension mismatch. Matrix A (' + asize + ') must match Matrix B (' + bsize + ')');
    } // rows & columns


    var rows = asize[0];
    var columns = asize[1]; // datatype

    var dt; // equal signature to use

    var eq = equalScalar; // zero value

    var zero = 0; // callback signature to use

    var cf = callback; // process data types

    if (typeof adt === 'string' && adt === bdt) {
      // datatype
      dt = adt; // find signature that matches (dt, dt)

      eq = typed.find(equalScalar, [dt, dt]); // convert 0 to the same datatype

      zero = typed.convert(0, dt); // callback

      cf = typed.find(callback, [dt, dt]);
    } // result arrays


    var cvalues = avalues && bvalues ? [] : undefined;
    var cindex = [];
    var cptr = []; // matrix

    var c = new SparseMatrix({
      values: cvalues,
      index: cindex,
      ptr: cptr,
      size: [rows, columns],
      datatype: dt
    }); // workspaces

    var xa = cvalues ? [] : undefined;
    var xb = cvalues ? [] : undefined; // marks indicating we have a value in x for a given column

    var wa = [];
    var wb = []; // vars

    var i, j, k, k1; // loop columns

    for (j = 0; j < columns; j++) {
      // update cptr
      cptr[j] = cindex.length; // columns mark

      var mark = j + 1; // loop values A(:,j)

      for (k = aptr[j], k1 = aptr[j + 1]; k < k1; k++) {
        // row
        i = aindex[k]; // push index

        cindex.push(i); // update workspace

        wa[i] = mark; // check we need to process values

        if (xa) {
          xa[i] = avalues[k];
        }
      } // loop values B(:,j)


      for (k = bptr[j], k1 = bptr[j + 1]; k < k1; k++) {
        // row
        i = bindex[k]; // check row existed in A

        if (wa[i] !== mark) {
          // push index
          cindex.push(i);
        } // update workspace


        wb[i] = mark; // check we need to process values

        if (xb) {
          xb[i] = bvalues[k];
        }
      } // check we need to process values (non pattern matrix)


      if (cvalues) {
        // initialize first index in j
        k = cptr[j]; // loop index in j

        while (k < cindex.length) {
          // row
          i = cindex[k]; // marks

          var wai = wa[i];
          var wbi = wb[i]; // check Aij or Bij are nonzero

          if (wai === mark || wbi === mark) {
            // matrix values @ i,j
            var va = wai === mark ? xa[i] : zero;
            var vb = wbi === mark ? xb[i] : zero; // Cij

            var vc = cf(va, vb); // check for zero

            if (!eq(vc, zero)) {
              // push value
              cvalues.push(vc); // increment pointer

              k++;
            } else {
              // remove value @ i, do not increment pointer
              cindex.splice(k, 1);
            }
          }
        }
      }
    } // update cptr


    cptr[columns] = cindex.length; // return sparse matrix

    return c;
  };

  return algorithm05;
}

exports.name = 'algorithm05';
exports.factory = factory;