Databases
StackOverflow2013
Postsdbo
POIs there a more efficient way of multiplying polynomials?
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POIs there a more efficient way of multiplying polynomials?
    primarykey
    data
    text
    <p>Here is my method for multiplying two polynomials of the form <code>an*x^n + an-1*x^n-1 + ... + a1*x + a0</code>. Each <code>Term</code> object has two fields: <code>double coefficient</code> and <code>int power</code>. <code>Polynomial</code> represents a polynomial by storing the terms in an <code>ArrayList&lt;Term&gt;</code>. This current implementation of multiply is O(n^2). Any ideas or hints on how to make it faster?</p> <pre><code>public Polynomial multiply(Polynomial P2) { PolynomialImp result = new PolynomialImp(); for (Term currentThisTerm : this.terms) { for (Term currentP2Term : ((PolynomialImp) P2).terms) { result.addTerm(new TermImp(currentThisTerm.getCoefficient()*currentP2Term.getCoefficient(), currentThisTerm.getExponent() + currentP2Term.getExponent())); } } //Sort polynomial in decreasing exponent order return result.sort(); } </code></pre> <p>Below is the addTerm method if needed:</p> <pre><code>private void addTerm(Term nextTerm) { for (int i = 0; i &lt; this.terms.size(); i++) { if (this.terms.get(i).getExponent() == nextTerm.getExponent()) { //Add the coefficients if the current term has the same exponent as a term that is already in the polynomial. //This preserves the sorting of the polynomial except during multiply. this.terms.set(i, new TermImp(this.terms.get(i).getCoefficient() + nextTerm.getCoefficient(), this.terms.get(i).getExponent())); return; } } //Avoid adding zeros to the polynomial. if (nextTerm.getCoefficient() != 0) this.terms.add(nextTerm); } </code></pre>
    singulars
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PTQuestion
    1. This table or related slice is empty.
    1. UScrzrcn
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    3. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POIs there a more efficient way of multiplying polynomials?
      1. This table or related slice is empty.
      1. VTUpMod
    1. COI would use arrays of `double[]` with the co-efficient for each power. This would still be O(n^2) to perform a multiplication. Are you sure you need it to be faster?
      singulars
      1. POIs there a more efficient way of multiplying polynomials?
      1. USPeter Lawrey
    2. COI don't need it to be faster, but I figured I might try for learns and giggles.
      singulars
      1. POIs there a more efficient way of multiplying polynomials?
      1. UScrzrcn
    3. COPolynomial Multiplication is O(n^2) unless you use FFT
      singulars
      1. POIs there a more efficient way of multiplying polynomials?
      1. USgtgaxiola
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload