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'use strict';
export const mutation_type = Object.freeze({
none: 'none',
source: 'source',
sink: 'sink',
weight: 'weight',
});
// clamp a number in the range [0, infinity)
function nonneg(x) {
if (x < 0) {
return 0;
} else {
return x;
}
}
// mutate a gene
export function mutate(gene, type, value) {
const [ source, sink, weight ] = gene;
switch(type) {
case mutation_type.none:
return [...gene];
case mutation_type.source:
if (value <= 0.5) {
return [ nonneg(source-1), sink, weight ];
} else {
return [ source+1, sink, weight ];
}
case mutation_type.sink:
if (value <= 0.5) {
return [ source, nonneg(sink-1), weight ];
} else {
return [ source, sink+1, weight ];
}
case mutation_type.weight:
const w = (8*value) - 4;
return [ source, sink, 0.5*(w + weight) ];
default:
throw new Error(`unknown mutation type: '${type}'`);
};
}
// check if a given genome is valid and compute its size
export function get_size(num_input, num_output, genome) {
const [ max_index, max_weight ] = genome.reduce(
([max_index, max_weight ], [ source, sink, weight]) => [
Math.max(max_index, source, sink),
Math.max(max_weight, Math.abs(weight)),
],
[ 0, 0 ]
);
if (max_index < num_input + num_output - 1) {
return -1;
}
else if (max_weight > 4.0) {
return -1;
}
else {
return max_index + 1;
}
}
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