source code
/* The Computer Language Benchmarks Game
http://benchmarksgame.alioth.debian.org/
contributed by Brad Chamberlain
derived from the Swift version by Ralph Ganszky
and the Chapel version by Nelson et al.
*/
use DynamicIters;
config const n = 200, // image size in pixels (n x n)
maxIter = 50, // max # of iterations per pixel
limit = 4.0, // per-pixel convergence limit
chunkSize = 1; // dynamic iterator's chunk size
param bitsPerElt = 8; // # of bits to store per array element
type eltType = uint(bitsPerElt); // element type used to store the image
proc main() {
const xsize = divceilpos(n, bitsPerElt), // the compacted x dimension
imgSpace = {0..#n, 0..#xsize}; // the compacted image size
var image : [imgSpace] eltType, // the compacted image
xval, yval: [0..#n] real; // pre-computed (x,y) values
// precompute (x, y) values from the complex plane
const inv = 2.0 / n;
forall i in 0..#n {
xval[i] = inv*i - 1.5;
yval[i] = inv*i - 1.0;
}
// compute the image
forall (y, xelt) in dynamic(imgSpace, chunkSize) {
const xbase = xelt*bitsPerElt,
cr = (xval[xbase+0], xval[xbase+1], xval[xbase+2], xval[xbase+3],
xval[xbase+4], xval[xbase+5], xval[xbase+6], xval[xbase+7]),
ci = yval[y];
var Zr, Zi, Tr, Ti: bitsPerElt*real;
for 1..maxIter { // for the max # of iterations
Zi = 2.0*Zr*Zi + ci; // update Z and T
Zr = Tr - Ti + cr;
Tr = Zr*Zr;
Ti = Zi*Zi;
if (Tr + Ti > limit) then // break out if we haven't converged
break;
}
// store 'bitsPerElt' pixels compactly into the final image
var pixval: eltType;
for param i in 1..bitsPerElt do
if (Tr(i) + Ti(i) <= limit) then // if 'C' is within the limit,
pixval |= 0x1 << (bitsPerElt-i); // turn the corresponding pixel on
image[y, xelt] = pixval;
}
// Get a lock-free writer channel on 'stdout'
var w = openfd(1).writer(iokind.native, locking=false);
// Write the file header and the image array.
w.writef("P4\n");
w.writef("%i %i\n", n, n);
w.write(image);
}
//
// Helper functions to add/compare an 8-tuple and a singleton
//
inline proc +(cr, ci) {
return (cr(1)+ci, cr(2)+ci, cr(3)+ci, cr(4)+ci,
cr(5)+ci, cr(6)+ci, cr(7)+ci, cr(8)+ci);
}
inline proc >(x, y) {
for param i in 1..bitsPerElt do
if x(i) <= y then
return false;
return true;
}