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Comment by stouset | Hacker News Reader

> For example, if you have a variable 'v' and want to update it to a new value 'f', you can do 'if (v == f)' to check if the variable would change.

Isn't it strictly faster to simply assign? No branching, no branch predictions, only one instruction in all cases.

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A typically pattern is:

  float freq = getParameter(FILTER_FREQUENCY);
  float coeff;
  if (freq != mFreq) {
    coeff = calculateCoeffFromFrequency(freq); // expensive
    mFreq = freq;
    mCoeff = coeff;
  } else {
    coeff = mCoeff; // use cached value
  }
  // use coeff

Could you do some threshold-based comparison? What if freq is changed only a little tiny bit?

I can certainly imagine cases where this would make sense.

Assuming that all you want to do is assign, then sure. If you want to log the change or do any additional conditional logic, then that wouldn't work.

It depends on whether you need a set operation or a test-and-set operation.

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