[MATH-1530] Spline interpolation : Avoid recomputing indexes when possible

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Done
• Fix Version/s: 4.0
• Assignee: Unassigned
• Reporter: Yassine Damerdji
• Created: 06/Apr/20 03:06
• Updated: 07/Apr/20 17:29
• Resolved: 07/Apr/20 17:29

Description

In org.apache.commons.math4.analysis.interpolation.SplineInterpolator and in org.apache.commons.math4.analysis.interpolation.AkimaSplineInterpolator, many indices are recomputed many times.

Example :

for (int i = 1; i < n; i++) {
    g = 2d * (x[i+1] - x[i - 1]) - h[i - 1] * mu[i -1];
    mu[i] = h[i] / g;
}

can be replaced by :

while (i < n) {
    g[i] = 2d * (x[iPlusOne] - x[iMinusOne]) - h[iMinusOne] * mu[iMinusOne];
    mu[i] = h[i] / g[i];
    iMinusOne = i;
    i = iPlusOne;
    iPlusOne = iPlusOne + 1;
}

In my tests, I saved almost 2% of processing time with this optimization.