/**
* Convert data to probability co-occurrences (aka calculating the kernel)
*
* @param d the data to convert
* @param u the perplexity of the model
* @return the probabilities of co-occurrence
*/
public INDArray computeGaussianPerplexity(final INDArray d, double u) {
int n = d.rows();
final INDArray p = zeros(n, n);
final INDArray beta = ones(n, 1);
final double logU = Math.log(u);
log.info("Calculating probabilities of data similarities..");
for (int i = 0; i < n; i++) {
if (i % 500 == 0 && i > 0) log.info("Handled " + i + " records");
double betaMin = Double.NEGATIVE_INFINITY;
double betaMax = Double.POSITIVE_INFINITY;
int[] vals = Ints.concat(ArrayUtil.range(0, i), ArrayUtil.range(i + 1, d.columns()));
INDArrayIndex[] range = new INDArrayIndex[] {new NDArrayIndex(vals)};
INDArray row = d.slice(i).get(range);
Pair<INDArray, INDArray> pair = hBeta(row, beta.getDouble(i));
INDArray hDiff = pair.getFirst().sub(logU);
int tries = 0;
// while hdiff > tolerance
while (BooleanIndexing.and(abs(hDiff), Conditions.greaterThan(tolerance)) && tries < 50) {
// if hdiff > 0
if (BooleanIndexing.and(hDiff, Conditions.greaterThan(0))) {
if (Double.isInfinite(betaMax)) beta.putScalar(i, beta.getDouble(i) * 2.0);
else beta.putScalar(i, (beta.getDouble(i) + betaMax) / 2.0);
betaMin = beta.getDouble(i);
} else {
if (Double.isInfinite(betaMin)) beta.putScalar(i, beta.getDouble(i) / 2.0);
else beta.putScalar(i, (beta.getDouble(i) + betaMin) / 2.0);
betaMax = beta.getDouble(i);
}
pair = hBeta(row, beta.getDouble(i));
hDiff = pair.getFirst().subi(logU);
tries++;
}
p.slice(i).put(range, pair.getSecond());
}
// dont need data in memory after
log.info("Mean value of sigma " + sqrt(beta.rdiv(1)).mean(Integer.MAX_VALUE));
BooleanIndexing.applyWhere(p, Conditions.isNan(), new Value(realMin));
// set 0 along the diagonal
INDArray permute = p.transpose();
INDArray pOut = p.add(permute);
pOut.divi(pOut.sum(Integer.MAX_VALUE));
BooleanIndexing.applyWhere(
pOut, Conditions.lessThan(Nd4j.EPS_THRESHOLD), new Value(Nd4j.EPS_THRESHOLD));
// ensure no nans
return pOut;
}
/**
* @param X
* @param nDims
* @param perplexity
*/
public INDArray calculate(INDArray X, int nDims, double perplexity) {
if (usePca) X = PCA.pca(X, Math.min(50, X.columns()), normalize);
// normalization (don't normalize again after pca)
if (normalize) {
X.subi(X.min(Integer.MAX_VALUE));
X = X.divi(X.max(Integer.MAX_VALUE));
X = X.subiRowVector(X.mean(0));
}
if (nDims > X.columns()) nDims = X.columns();
INDArray sumX = pow(X, 2).sum(1);
INDArray D = X.mmul(X.transpose()).muli(-2).addRowVector(sumX).transpose().addRowVector(sumX);
// output
if (y == null) y = randn(X.rows(), nDims, Nd4j.getRandom()).muli(1e-3f);
INDArray p = computeGaussianPerplexity(D, perplexity);
// lie for better local minima
p.muli(4);
// init adagrad where needed
if (useAdaGrad) {
if (adaGrad == null) {
adaGrad = new AdaGrad(y.shape());
adaGrad.setMasterStepSize(learningRate);
}
}
for (int i = 0; i < maxIter; i++) {
step(p, i);
if (i == switchMomentumIteration) momentum = finalMomentum;
if (i == stopLyingIteration) p.divi(4);
if (iterationListener != null) iterationListener.iterationDone(null, i);
}
return y;
}
