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/*
* http://local.wasp.uwa.edu.au/~pbourke/miscellaneous/dft/
Modification of Paul Bourkes FFT code by Peter Cusack
to utilise the Microsoft complex type.
This computes an in-place complex-to-complex FFT
x and y are the real and imaginary arrays of 2^m points.
dir = 1 gives forward transform
dir = -1 gives reverse transform
*/
import Math.{sqrt, pow}
/** Test that specialization handles tuples. Perform FFT transformation
* using pairs to represent complex numbers.
*/
object Test {
type Complex = (Double, Double)
def swap(x: Array[Complex], i: Int, j: Int) {
val tmp = x(i)
x(i) = x(j)
x(j) = tmp
}
def times(x: Complex, y: Complex): Complex =
(x._1 * y._1 - x._2 * y._2, x._1 * y._2 + x._2 * y._1)
def div(x: Complex, y: Complex): Complex = {
val num = pow(y._1, 2) + pow(y._2, 2)
((x._1 * y._1 + x._2 * y._2)/num,
(x._2 * y._1 - x._1 * y._2)/num)
}
def div(x: Complex, y: Long) =
(x._1 / y, x._2 / y)
def add(x: Complex, y: Complex) =
(x._1 + y._1, x._2 + y._2)
def minus(x: Complex, y: Complex) =
(x._1 - y._1, x._2 - y._2)
def FFT(dir: Int, m: Long, x: Array[(Double, Double)]) {
var i, i1, i2,j, k, l, l1, l2, n = 0l
// complex <double> tx, t1, u, c;
var tx, t1, u, c = (0.0, 0.0)
/*Calculate the number of points */
n = 1
for (i <- 0l until m)
n <<= 1
/* Do the bit reversal */
i2 = n >> 1
j = 0
for (i <- 0l until (n - 1)) {
if (i < j)
swap(x, i.toInt, j.toInt);
k = i2;
while (k <= j) {
j -= k;
k >>= 1;
}
j += k;
}
/* Compute the FFT */
// c.real(-1.0);
// c.imag(0.0);
c = (-1.0, 0.0)
l2 = 1
for (l <- 0l until m) {
l1 = l2
l2 <<= 1;
// u.real(1.0);
// u.imag(0.0);
u = (1.0, 0.0)
for (j <- 0l until l1) {
for (i <- j.until(n, l2)) {
i1 = i + l1;
t1 = times(u, x(i1.toInt))
x(i1.toInt) = minus(x(i.toInt), t1)
x(i.toInt) = add(x(i.toInt), t1)
}
u = times(u, c)
}
// c.imag(sqrt((1.0 - c.real()) / 2.0));
c = (c._1, sqrt( (1.0 - c._1) / 2.0 ))
// if (dir == 1)
// c.imag(-c.imag());
if (dir == 1)
c = (c._1, -c._2)
// c.real(sqrt((1.0 + c.real()) / 2.0));
c = (sqrt( (1.0 + c._1) / 2.0), c._2)
}
/* Scaling for forward transform */
if (dir == 1) {
for (i <- 0l until n)
x(i.toInt) = div(x(i.toInt), n)
}
}
def run() {
FFT(1, 16, data)
}
var data: Array[Complex] = null
def inputFileName = {
val cwd = System.getProperty("partest.cwd")
if (cwd ne null) cwd + java.io.File.separator + "input2.txt"
else "input2.txt"
}
def setUp {
// print("Loading from %s.. ".format(inputFileName))
val f = io.Source.fromFile(inputFileName)
val lines = f.getLines
val n = lines.next.toInt
data = new Array[Complex](n)
var i = 0
for (line <- lines if line != "") {
val pair = line.trim.split(" ")
data(i) = (pair(0).trim.toDouble, pair(1).trim.toDouble)
i += 1
}
// println("[loaded]")
println("Processing " + n + " items")
}
def main(args: Array[String]) {
setUp
run()
println("Boxed doubles: " + runtime.BoxesRunTime.doubleBoxCount)
println("Boxed ints: " + runtime.BoxesRunTime.integerBoxCount)
println("Boxed longs: " + runtime.BoxesRunTime.longBoxCount)
}
}
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