org.jtransforms.dht.DoubleDHT_1D Maven / Gradle / Ivy
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* Copyright (c) 2007 onward, Piotr Wendykier
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package org.jtransforms.dht;
import java.util.concurrent.Future;
import org.jtransforms.fft.DoubleFFT_1D;
import org.jtransforms.utils.CommonUtils;
import org.jtransforms.utils.ConcurrencyUtils;
import pl.edu.icm.jlargearrays.DoubleLargeArray;
import pl.edu.icm.jlargearrays.Utilities;
/**
* Computes 1D Discrete Hartley Transform (DHT) of real, double precision data.
* The size of the data can be an arbitrary number. It uses FFT algorithm. This
* is a parallel implementation optimized for SMP systems.
*
* @author Piotr Wendykier ([email protected])
*/
public class DoubleDHT_1D {
private final int n;
private final long nl;
private final DoubleFFT_1D fft;
private final boolean useLargeArrays;
/**
* Creates new instance of DoubleDHT_1D.
*
* @param n size of data
*/
public DoubleDHT_1D(long n) {
this.n = (int) n;
this.nl = n;
this.useLargeArrays = n >= ConcurrencyUtils.getLargeArraysBeginN();
fft = new DoubleFFT_1D(n);
}
/**
* Computes 1D real, forward DHT leaving the result in a.
*
* @param a data to transform
*/
public void forward(double[] a) {
forward(a, 0);
}
/**
* Computes 1D real, forward DHT leaving the result in a.
*
* @param a data to transform
*/
public void forward(DoubleLargeArray a) {
forward(a, 0);
}
/**
* Computes 1D real, forward DHT leaving the result in a.
*
* @param a data to transform
* @param offa index of the first element in array a
*/
public void forward(final double[] a, final int offa) {
if (n == 1) {
return;
}
if (useLargeArrays) {
forward(new DoubleLargeArray(a), offa);
} else {
fft.realForward(a, offa);
final double[] b = new double[n];
System.arraycopy(a, offa, b, 0, n);
int nd2 = n / 2;
int nthreads = ConcurrencyUtils.getNumberOfThreads();
if ((nthreads > 1) && (nd2 > ConcurrencyUtils.getThreadsBeginN_1D_FFT_2Threads())) {
nthreads = 2;
final int k1 = nd2 / nthreads;
Future[] futures = new Future[nthreads];
for (int i = 0; i < nthreads; i++) {
final int firstIdx = 1 + i * k1;
final int lastIdx = (i == (nthreads - 1)) ? nd2 : firstIdx + k1;
futures[i] = ConcurrencyUtils.submit(new Runnable() {
public void run() {
int idx1, idx2;
for (int i = firstIdx; i < lastIdx; i++) {
idx1 = 2 * i;
idx2 = idx1 + 1;
a[offa + i] = b[idx1] - b[idx2];
a[offa + n - i] = b[idx1] + b[idx2];
}
}
});
}
ConcurrencyUtils.waitForCompletion(futures);
} else {
int idx1, idx2;
for (int i = 1; i < nd2; i++) {
idx1 = 2 * i;
idx2 = idx1 + 1;
a[offa + i] = b[idx1] - b[idx2];
a[offa + n - i] = b[idx1] + b[idx2];
}
}
if ((n % 2) == 0) {
a[offa + nd2] = b[1];
} else {
a[offa + nd2] = b[n - 1] - b[1];
a[offa + nd2 + 1] = b[n - 1] + b[1];
}
}
}
/**
* Computes 1D real, forward DHT leaving the result in a.
*
* @param a data to transform
* @param offa index of the first element in array a
*/
public void forward(final DoubleLargeArray a, final long offa) {
if (nl == 1) {
return;
}
if (!useLargeArrays) {
if (a.getData() != null && offa < Integer.MAX_VALUE) {
forward(a.getData(), (int) offa);
} else {
throw new IllegalArgumentException("The data array is too big.");
}
} else {
fft.realForward(a, offa);
final DoubleLargeArray b = new DoubleLargeArray(nl, false);
Utilities.arraycopy(a, offa, b, 0, nl);
long nd2 = nl / 2;
int nthreads = ConcurrencyUtils.getNumberOfThreads();
if ((nthreads > 1) && (nd2 > ConcurrencyUtils.getThreadsBeginN_1D_FFT_2Threads())) {
nthreads = 2;
final long k1 = nd2 / nthreads;
Future[] futures = new Future[nthreads];
for (int i = 0; i < nthreads; i++) {
final long firstIdx = 1 + i * k1;
final long lastIdx = (i == (nthreads - 1)) ? nd2 : firstIdx + k1;
futures[i] = ConcurrencyUtils.submit(new Runnable() {
public void run() {
long idx1, idx2;
for (long i = firstIdx; i < lastIdx; i++) {
idx1 = 2 * i;
idx2 = idx1 + 1;
a.setDouble(offa + i, b.getDouble(idx1) - b.getDouble(idx2));
a.setDouble(offa + nl - i, b.getDouble(idx1) + b.getDouble(idx2));
}
}
});
}
ConcurrencyUtils.waitForCompletion(futures);
} else {
long idx1, idx2;
for (long i = 1; i < nd2; i++) {
idx1 = 2 * i;
idx2 = idx1 + 1;
a.setDouble(offa + i, b.getDouble(idx1) - b.getDouble(idx2));
a.setDouble(offa + nl - i, b.getDouble(idx1) + b.getDouble(idx2));
}
}
if ((nl % 2) == 0) {
a.setDouble(offa + nd2, b.getDouble(1));
} else {
a.setDouble(offa + nd2, b.getDouble(nl - 1) - b.getDouble(1));
a.setDouble(offa + nd2 + 1, b.getDouble(nl - 1) + b.getDouble(1));
}
}
}
/**
* Computes 1D real, inverse DHT leaving the result in a.
*
* @param a data to transform
* @param scale if true then scaling is performed
*/
public void inverse(double[] a, boolean scale) {
inverse(a, 0, scale);
}
/**
* Computes 1D real, inverse DHT leaving the result in a.
*
* @param a data to transform
* @param scale if true then scaling is performed
*/
public void inverse(DoubleLargeArray a, boolean scale) {
inverse(a, 0, scale);
}
/**
* Computes 1D real, inverse DHT leaving the result in a.
*
* @param a data to transform
* @param offa index of the first element in array a
* @param scale if true then scaling is performed
*/
public void inverse(final double[] a, final int offa, boolean scale) {
if (n == 1) {
return;
}
if (useLargeArrays) {
inverse(new DoubleLargeArray(a), offa, scale);
} else {
forward(a, offa);
if (scale) {
CommonUtils.scale(n, 1.0 / n, a, offa, false);
}
}
}
/**
* Computes 1D real, inverse DHT leaving the result in a.
*
* @param a data to transform
* @param offa index of the first element in array a
* @param scale if true then scaling is performed
*/
public void inverse(final DoubleLargeArray a, final long offa, boolean scale) {
if (n == 1) {
return;
}
if (!useLargeArrays) {
if (a.getData() != null && offa < Integer.MAX_VALUE) {
inverse(a.getData(), (int) offa, scale);
} else {
throw new IllegalArgumentException("The data array is too big.");
}
} else {
forward(a, offa);
if (scale) {
CommonUtils.scale(n, 1.0 / n, a, offa, false);
}
}
}
}
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