Forward error
= Forward error
{title2=$\widehat{x}-x_*$}
The <forward error> is the difference between a computed result $\widehat{x}$ and the exact result $x_*$ for the original data. Its size can be measured by a <norm>, or relative to $\|x_*\|$ when $x_*\ne0$. A <linear-system residual> measures the equation imbalance instead; the <condition number> relates that imbalance to the <forward error>.