Difference between revisions of "Selection"
From Adaptive Population based Simplex
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== Basic selection (s0) == | == Basic selection (s0) == | ||
# Select a simplex S (i.e. D+1 individuals) at random. Be sure that the current one is in this list. If not, replace the last of the list by the current one. | # Select a simplex S (i.e. D+1 individuals) at random. Be sure that the current one is in this list. If not, replace the last of the list by the current one. | ||
| − | |||
# Select the three first ones. | # Select the three first ones. | ||
# Sort them, by increasing order of value (fitness). They are xbest, xworst2, and wworst. | # Sort them, by increasing order of value (fitness). They are xbest, xworst2, and wworst. | ||
If xbest is better than the best ever found (i.e. Best), set Best=xbest. | If xbest is better than the best ever found (i.e. Best), set Best=xbest. | ||
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| + | === Adaptive probability === | ||
| + | Compute the volume V(1) of the simplex. If the previous volume is zero (in practice, too small) the probability p is set to 0.5. If not, the formula is | ||
| + | $$ | ||
| + | p=\frac{1}{1+e^{-\frac{V(1)-V(0)}{V(0)}}} | ||
| + | $$ | ||
| + | |||
| + | The rationale is the following:<br /> | ||
| + | the more the simplex volume increases, the less the algorithm is successful, and the more one needs randomness to increase the diversity. | ||
Revision as of 18:12, 28 June 2013
Basic selection (s0)
- Select a simplex S (i.e. D+1 individuals) at random. Be sure that the current one is in this list. If not, replace the last of the list by the current one.
- Select the three first ones.
- Sort them, by increasing order of value (fitness). They are xbest, xworst2, and wworst.
If xbest is better than the best ever found (i.e. Best), set Best=xbest.
Adaptive probability
Compute the volume V(1) of the simplex. If the previous volume is zero (in practice, too small) the probability p is set to 0.5. If not, the formula is p=11+e−V(1)−V(0)V(0)
The rationale is the following:
the more the simplex volume increases, the less the algorithm is successful, and the more one needs randomness to increase the diversity.
