benchmarks/navier-stokes.js - v8/v8.git - Git at Google

 /**
  * Copyright 2012 the V8 project authors. All rights reserved.
  * Copyright 2009 Oliver Hunt <http://nerget.com>
  *
  * Permission is hereby granted, free of charge, to any person
  * obtaining a copy of this software and associated documentation
  * files (the "Software"), to deal in the Software without
  * restriction, including without limitation the rights to use,
  * copy, modify, merge, publish, distribute, sublicense, and/or sell
  * copies of the Software, and to permit persons to whom the
  * Software is furnished to do so, subject to the following
  * conditions:
  *
  * The above copyright notice and this permission notice shall be
  * included in all copies or substantial portions of the Software.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
  * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
  * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
  * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
  * OTHER DEALINGS IN THE SOFTWARE.
  */

 var NavierStokes = new BenchmarkSuite('NavierStokes', 1484000,
                                       [new Benchmark('NavierStokes',
                                                      runNavierStokes,
                                                      setupNavierStokes,
                                                      tearDownNavierStokes)]);

 var solver = null;

 function runNavierStokes()
 {
     solver.update();
 }

 function setupNavierStokes()
 {
     solver = new FluidField(null);
     solver.setResolution(128, 128);
     solver.setIterations(20);
     solver.setDisplayFunction(function(){});
     solver.setUICallback(prepareFrame);
     solver.reset();
 }

 function tearDownNavierStokes()
 {
     solver = null;
 }

 function addPoints(field) {
     var n = 64;
     for (var i = 1; i <= n; i++) {
         field.setVelocity(i, i, n, n);
         field.setDensity(i, i, 5);
         field.setVelocity(i, n - i, -n, -n);
         field.setDensity(i, n - i, 20);
         field.setVelocity(128 - i, n + i, -n, -n);
         field.setDensity(128 - i, n + i, 30);
     }
 }

 var framesTillAddingPoints = 0;
 var framesBetweenAddingPoints = 5;

 function prepareFrame(field)
 {
     if (framesTillAddingPoints == 0) {
         addPoints(field);
         framesTillAddingPoints = framesBetweenAddingPoints;
         framesBetweenAddingPoints++;
     } else {
         framesTillAddingPoints--;
     }
 }

 // Code from Oliver Hunt (http://nerget.com/fluidSim/pressure.js) starts here.
 function FluidField(canvas) {
     function addFields(x, s, dt)
     {
         for (var i=0; i<size ; i++ ) x[i] += dt*s[i];
     }

     function set_bnd(b, x)
     {
         if (b===1) {
             for (var i = 1; i <= width; i++) {
                 x[i] =  x[i + rowSize];
                 x[i + (height+1) *rowSize] = x[i + height * rowSize];
             }

             for (var j = 1; i <= height; i++) {
                 x[j * rowSize] = -x[1 + j * rowSize];
                 x[(width + 1) + j * rowSize] = -x[width + j * rowSize];
             }
         } else if (b === 2) {
             for (var i = 1; i <= width; i++) {
                 x[i] = -x[i + rowSize];
                 x[i + (height + 1) * rowSize] = -x[i + height * rowSize];
             }

             for (var j = 1; j <= height; j++) {
                 x[j * rowSize] =  x[1 + j * rowSize];
                 x[(width + 1) + j * rowSize] =  x[width + j * rowSize];
             }
         } else {
             for (var i = 1; i <= width; i++) {
                 x[i] =  x[i + rowSize];
                 x[i + (height + 1) * rowSize] = x[i + height * rowSize];
             }

             for (var j = 1; j <= height; j++) {
                 x[j * rowSize] =  x[1 + j * rowSize];
                 x[(width + 1) + j * rowSize] =  x[width + j * rowSize];
             }
         }
         var maxEdge = (height + 1) * rowSize;
         x[0]                 = 0.5 * (x[1] + x[rowSize]);
         x[maxEdge]           = 0.5 * (x[1 + maxEdge] + x[height * rowSize]);
         x[(width+1)]         = 0.5 * (x[width] + x[(width + 1) + rowSize]);
         x[(width+1)+maxEdge] = 0.5 * (x[width + maxEdge] + x[(width + 1) + height * rowSize]);
     }

     function lin_solve(b, x, x0, a, c)
     {
         if (a === 0 && c === 1) {
             for (var j=1 ; j<=height; j++) {
                 var currentRow = j * rowSize;
                 ++currentRow;
                 for (var i = 0; i < width; i++) {
                     x[currentRow] = x0[currentRow];
                     ++currentRow;
                 }
             }
             set_bnd(b, x);
         } else {
             var invC = 1 / c;
             for (var k=0 ; k<iterations; k++) {
                 for (var j=1 ; j<=height; j++) {
                     var lastRow = (j - 1) * rowSize;
                     var currentRow = j * rowSize;
                     var nextRow = (j + 1) * rowSize;
                     var lastX = x[currentRow];
                     ++currentRow;
                     for (var i=1; i<=width; i++)
                         lastX = x[currentRow] = (x0[currentRow] + a*(lastX+x[++currentRow]+x[++lastRow]+x[++nextRow])) * invC;
                 }
                 set_bnd(b, x);
             }
         }
     }

     function diffuse(b, x, x0, dt)
     {
         var a = 0;
         lin_solve(b, x, x0, a, 1 + 4*a);
     }

     function lin_solve2(x, x0, y, y0, a, c)
     {
         if (a === 0 && c === 1) {
             for (var j=1 ; j <= height; j++) {
                 var currentRow = j * rowSize;
                 ++currentRow;
                 for (var i = 0; i < width; i++) {
                     x[currentRow] = x0[currentRow];
                     y[currentRow] = y0[currentRow];
                     ++currentRow;
                 }
             }
             set_bnd(1, x);
             set_bnd(2, y);
         } else {
             var invC = 1/c;
             for (var k=0 ; k<iterations; k++) {
                 for (var j=1 ; j <= height; j++) {
                     var lastRow = (j - 1) * rowSize;
                     var currentRow = j * rowSize;
                     var nextRow = (j + 1) * rowSize;
                     var lastX = x[currentRow];
                     var lastY = y[currentRow];
                     ++currentRow;
                     for (var i = 1; i <= width; i++) {
                         lastX = x[currentRow] = (x0[currentRow] + a * (lastX + x[currentRow] + x[lastRow] + x[nextRow])) * invC;
                         lastY = y[currentRow] = (y0[currentRow] + a * (lastY + y[++currentRow] + y[++lastRow] + y[++nextRow])) * invC;
                     }
                 }
                 set_bnd(1, x);
                 set_bnd(2, y);
             }
         }
     }

     function diffuse2(x, x0, y, y0, dt)
     {
         var a = 0;
         lin_solve2(x, x0, y, y0, a, 1 + 4 * a);
     }

     function advect(b, d, d0, u, v, dt)
     {
         var Wdt0 = dt * width;
         var Hdt0 = dt * height;
         var Wp5 = width + 0.5;
         var Hp5 = height + 0.5;
         for (var j = 1; j<= height; j++) {
             var pos = j * rowSize;
             for (var i = 1; i <= width; i++) {
                 var x = i - Wdt0 * u[++pos];
                 var y = j - Hdt0 * v[pos];
                 if (x < 0.5)
                     x = 0.5;
                 else if (x > Wp5)
                     x = Wp5;
                 var i0 = x | 0;
                 var i1 = i0 + 1;
                 if (y < 0.5)
                     y = 0.5;
                 else if (y > Hp5)
                     y = Hp5;
                 var j0 = y | 0;
                 var j1 = j0 + 1;
                 var s1 = x - i0;
                 var s0 = 1 - s1;
                 var t1 = y - j0;
                 var t0 = 1 - t1;
                 var row1 = j0 * rowSize;
                 var row2 = j1 * rowSize;
                 d[pos] = s0 * (t0 * d0[i0 + row1] + t1 * d0[i0 + row2]) + s1 * (t0 * d0[i1 + row1] + t1 * d0[i1 + row2]);
             }
         }
         set_bnd(b, d);
     }

     function project(u, v, p, div)
     {
         var h = -0.5 / Math.sqrt(width * height);
         for (var j = 1 ; j <= height; j++ ) {
             var row = j * rowSize;
             var previousRow = (j - 1) * rowSize;
             var prevValue = row - 1;
             var currentRow = row;
             var nextValue = row + 1;
             var nextRow = (j + 1) * rowSize;
             for (var i = 1; i <= width; i++ ) {
                 div[++currentRow] = h * (u[++nextValue] - u[++prevValue] + v[++nextRow] - v[++previousRow]);
                 p[currentRow] = 0;
             }
         }
         set_bnd(0, div);
         set_bnd(0, p);

         lin_solve(0, p, div, 1, 4 );
         var wScale = 0.5 * width;
         var hScale = 0.5 * height;
         for (var j = 1; j<= height; j++ ) {
             var prevPos = j * rowSize - 1;
             var currentPos = j * rowSize;
             var nextPos = j * rowSize + 1;
             var prevRow = (j - 1) * rowSize;
             var currentRow = j * rowSize;
             var nextRow = (j + 1) * rowSize;

             for (var i = 1; i<= width; i++) {
                 u[++currentPos] -= wScale * (p[++nextPos] - p[++prevPos]);
                 v[currentPos]   -= hScale * (p[++nextRow] - p[++prevRow]);
             }
         }
         set_bnd(1, u);
         set_bnd(2, v);
     }

     function dens_step(x, x0, u, v, dt)
     {
         addFields(x, x0, dt);
         diffuse(0, x0, x, dt );
         advect(0, x, x0, u, v, dt );
     }

     function vel_step(u, v, u0, v0, dt)
     {
         addFields(u, u0, dt );
         addFields(v, v0, dt );
         var temp = u0; u0 = u; u = temp;
         var temp = v0; v0 = v; v = temp;
         diffuse2(u,u0,v,v0, dt);
         project(u, v, u0, v0);
         var temp = u0; u0 = u; u = temp;
         var temp = v0; v0 = v; v = temp;
         advect(1, u, u0, u0, v0, dt);
         advect(2, v, v0, u0, v0, dt);
         project(u, v, u0, v0 );
     }
     var uiCallback = function(d,u,v) {};

     function Field(dens, u, v) {
         // Just exposing the fields here rather than using accessors is a measurable win during display (maybe 5%)
         // but makes the code ugly.
         this.setDensity = function(x, y, d) {
              dens[(x + 1) + (y + 1) * rowSize] = d;
         }
         this.getDensity = function(x, y) {
              return dens[(x + 1) + (y + 1) * rowSize];
         }
         this.setVelocity = function(x, y, xv, yv) {
              u[(x + 1) + (y + 1) * rowSize] = xv;
              v[(x + 1) + (y + 1) * rowSize] = yv;
         }
         this.getXVelocity = function(x, y) {
              return u[(x + 1) + (y + 1) * rowSize];
         }
         this.getYVelocity = function(x, y) {
              return v[(x + 1) + (y + 1) * rowSize];
         }
         this.width = function() { return width; }
         this.height = function() { return height; }
     }
     function queryUI(d, u, v)
     {
         for (var i = 0; i < size; i++)
             u[i] = v[i] = d[i] = 0.0;
         uiCallback(new Field(d, u, v));
     }

     this.update = function () {
         queryUI(dens_prev, u_prev, v_prev);
         vel_step(u, v, u_prev, v_prev, dt);
         dens_step(dens, dens_prev, u, v, dt);
         displayFunc(new Field(dens, u, v));
     }
     this.setDisplayFunction = function(func) {
         displayFunc = func;
     }

     this.iterations = function() { return iterations; }
     this.setIterations = function(iters) {
         if (iters > 0 && iters <= 100)
            iterations = iters;
     }
     this.setUICallback = function(callback) {
         uiCallback = callback;
     }
     var iterations = 10;
     var visc = 0.5;
     var dt = 0.1;
     var dens;
     var dens_prev;
     var u;
     var u_prev;
     var v;
     var v_prev;
     var width;
     var height;
     var rowSize;
     var size;
     var displayFunc;
     function reset()
     {
         rowSize = width + 2;
         size = (width+2)*(height+2);
         dens = new Array(size);
         dens_prev = new Array(size);
         u = new Array(size);
         u_prev = new Array(size);
         v = new Array(size);
         v_prev = new Array(size);
         for (var i = 0; i < size; i++)
             dens_prev[i] = u_prev[i] = v_prev[i] = dens[i] = u[i] = v[i] = 0;
     }
     this.reset = reset;
     this.setResolution = function (hRes, wRes)
     {
         var res = wRes * hRes;
         if (res > 0 && res < 1000000 && (wRes != width || hRes != height)) {
             width = wRes;
             height = hRes;
             reset();
             return true;
         }
         return false;
     }
     this.setResolution(64, 64);
 }
	/**
	* Copyright 2012 the V8 project authors. All rights reserved.
	* Copyright 2009 Oliver Hunt <http://nerget.com>
	*
	* Permission is hereby granted, free of charge, to any person
	* obtaining a copy of this software and associated documentation
	* files (the "Software"), to deal in the Software without
	* restriction, including without limitation the rights to use,
	* copy, modify, merge, publish, distribute, sublicense, and/or sell
	* copies of the Software, and to permit persons to whom the
	* Software is furnished to do so, subject to the following
	* conditions:
	*
	* The above copyright notice and this permission notice shall be
	* included in all copies or substantial portions of the Software.
	*
	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
	* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
	* OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
	* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
	* HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
	* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
	* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
	* OTHER DEALINGS IN THE SOFTWARE.
	*/

	var NavierStokes = new BenchmarkSuite('NavierStokes', 1484000,
	[new Benchmark('NavierStokes',
	runNavierStokes,
	setupNavierStokes,
	tearDownNavierStokes)]);

	var solver = null;

	function runNavierStokes()
	{
	solver.update();
	}

	function setupNavierStokes()
	{
	solver = new FluidField(null);
	solver.setResolution(128, 128);
	solver.setIterations(20);
	solver.setDisplayFunction(function(){});
	solver.setUICallback(prepareFrame);
	solver.reset();
	}

	function tearDownNavierStokes()
	{
	solver = null;
	}

	function addPoints(field) {
	var n = 64;
	for (var i = 1; i <= n; i++) {
	field.setVelocity(i, i, n, n);
	field.setDensity(i, i, 5);
	field.setVelocity(i, n - i, -n, -n);
	field.setDensity(i, n - i, 20);
	field.setVelocity(128 - i, n + i, -n, -n);
	field.setDensity(128 - i, n + i, 30);
	}
	}

	var framesTillAddingPoints = 0;
	var framesBetweenAddingPoints = 5;

	function prepareFrame(field)
	{
	if (framesTillAddingPoints == 0) {
	addPoints(field);
	framesTillAddingPoints = framesBetweenAddingPoints;
	framesBetweenAddingPoints++;
	} else {
	framesTillAddingPoints--;
	}
	}

	// Code from Oliver Hunt (http://nerget.com/fluidSim/pressure.js) starts here.
	function FluidField(canvas) {
	function addFields(x, s, dt)
	{
	for (var i=0; i<size ; i++ ) x[i] += dt*s[i];
	}

	function set_bnd(b, x)
	{
	if (b===1) {
	for (var i = 1; i <= width; i++) {
	x[i] = x[i + rowSize];
	x[i + (height+1) rowSize] = x[i + height rowSize];
	}

	for (var j = 1; i <= height; i++) {
	x[j * rowSize] = -x[1 + j * rowSize];
	x[(width + 1) + j * rowSize] = -x[width + j * rowSize];
	}
	} else if (b === 2) {
	for (var i = 1; i <= width; i++) {
	x[i] = -x[i + rowSize];
	x[i + (height + 1) * rowSize] = -x[i + height * rowSize];
	}

	for (var j = 1; j <= height; j++) {
	x[j * rowSize] = x[1 + j * rowSize];
	x[(width + 1) + j * rowSize] = x[width + j * rowSize];
	}
	} else {
	for (var i = 1; i <= width; i++) {
	x[i] = x[i + rowSize];
	x[i + (height + 1) * rowSize] = x[i + height * rowSize];
	}

	for (var j = 1; j <= height; j++) {
	x[j * rowSize] = x[1 + j * rowSize];
	x[(width + 1) + j * rowSize] = x[width + j * rowSize];
	}
	}
	var maxEdge = (height + 1) * rowSize;
	x[0] = 0.5 * (x[1] + x[rowSize]);
	x[maxEdge] = 0.5 * (x[1 + maxEdge] + x[height * rowSize]);
	x[(width+1)] = 0.5 * (x[width] + x[(width + 1) + rowSize]);
	x[(width+1)+maxEdge] = 0.5 * (x[width + maxEdge] + x[(width + 1) + height * rowSize]);
	}

	function lin_solve(b, x, x0, a, c)
	{
	if (a === 0 && c === 1) {
	for (var j=1 ; j<=height; j++) {
	var currentRow = j * rowSize;
	++currentRow;
	for (var i = 0; i < width; i++) {
	x[currentRow] = x0[currentRow];
	++currentRow;
	}
	}
	set_bnd(b, x);
	} else {
	var invC = 1 / c;
	for (var k=0 ; k<iterations; k++) {
	for (var j=1 ; j<=height; j++) {
	var lastRow = (j - 1) * rowSize;
	var currentRow = j * rowSize;
	var nextRow = (j + 1) * rowSize;
	var lastX = x[currentRow];
	++currentRow;
	for (var i=1; i<=width; i++)
	lastX = x[currentRow] = (x0[currentRow] + a(lastX+x[++currentRow]+x[++lastRow]+x[++nextRow])) invC;
	}
	set_bnd(b, x);
	}
	}
	}

	function diffuse(b, x, x0, dt)
	{
	var a = 0;
	lin_solve(b, x, x0, a, 1 + 4*a);
	}

	function lin_solve2(x, x0, y, y0, a, c)
	{
	if (a === 0 && c === 1) {
	for (var j=1 ; j <= height; j++) {
	var currentRow = j * rowSize;
	++currentRow;
	for (var i = 0; i < width; i++) {
	x[currentRow] = x0[currentRow];
	y[currentRow] = y0[currentRow];
	++currentRow;
	}
	}
	set_bnd(1, x);
	set_bnd(2, y);
	} else {
	var invC = 1/c;
	for (var k=0 ; k<iterations; k++) {
	for (var j=1 ; j <= height; j++) {
	var lastRow = (j - 1) * rowSize;
	var currentRow = j * rowSize;
	var nextRow = (j + 1) * rowSize;
	var lastX = x[currentRow];
	var lastY = y[currentRow];
	++currentRow;
	for (var i = 1; i <= width; i++) {
	lastX = x[currentRow] = (x0[currentRow] + a * (lastX + x[currentRow] + x[lastRow] + x[nextRow])) * invC;
	lastY = y[currentRow] = (y0[currentRow] + a * (lastY + y[++currentRow] + y[++lastRow] + y[++nextRow])) * invC;
	}
	}
	set_bnd(1, x);
	set_bnd(2, y);
	}
	}
	}

	function diffuse2(x, x0, y, y0, dt)
	{
	var a = 0;
	lin_solve2(x, x0, y, y0, a, 1 + 4 * a);
	}

	function advect(b, d, d0, u, v, dt)
	{
	var Wdt0 = dt * width;
	var Hdt0 = dt * height;
	var Wp5 = width + 0.5;
	var Hp5 = height + 0.5;
	for (var j = 1; j<= height; j++) {
	var pos = j * rowSize;
	for (var i = 1; i <= width; i++) {
	var x = i - Wdt0 * u[++pos];
	var y = j - Hdt0 * v[pos];
	if (x < 0.5)
	x = 0.5;
	else if (x > Wp5)
	x = Wp5;
	var i0 = x \| 0;
	var i1 = i0 + 1;
	if (y < 0.5)
	y = 0.5;
	else if (y > Hp5)
	y = Hp5;
	var j0 = y \| 0;
	var j1 = j0 + 1;
	var s1 = x - i0;
	var s0 = 1 - s1;
	var t1 = y - j0;
	var t0 = 1 - t1;
	var row1 = j0 * rowSize;
	var row2 = j1 * rowSize;
	d[pos] = s0 * (t0 * d0[i0 + row1] + t1 * d0[i0 + row2]) + s1 * (t0 * d0[i1 + row1] + t1 * d0[i1 + row2]);
	}
	}
	set_bnd(b, d);
	}

	function project(u, v, p, div)
	{
	var h = -0.5 / Math.sqrt(width * height);
	for (var j = 1 ; j <= height; j++ ) {
	var row = j * rowSize;
	var previousRow = (j - 1) * rowSize;
	var prevValue = row - 1;
	var currentRow = row;
	var nextValue = row + 1;
	var nextRow = (j + 1) * rowSize;
	for (var i = 1; i <= width; i++ ) {
	div[++currentRow] = h * (u[++nextValue] - u[++prevValue] + v[++nextRow] - v[++previousRow]);
	p[currentRow] = 0;
	}
	}
	set_bnd(0, div);
	set_bnd(0, p);

	lin_solve(0, p, div, 1, 4 );
	var wScale = 0.5 * width;
	var hScale = 0.5 * height;
	for (var j = 1; j<= height; j++ ) {
	var prevPos = j * rowSize - 1;
	var currentPos = j * rowSize;
	var nextPos = j * rowSize + 1;
	var prevRow = (j - 1) * rowSize;
	var currentRow = j * rowSize;
	var nextRow = (j + 1) * rowSize;

	for (var i = 1; i<= width; i++) {
	u[++currentPos] -= wScale * (p[++nextPos] - p[++prevPos]);
	v[currentPos] -= hScale * (p[++nextRow] - p[++prevRow]);
	}
	}
	set_bnd(1, u);
	set_bnd(2, v);
	}

	function dens_step(x, x0, u, v, dt)
	{
	addFields(x, x0, dt);
	diffuse(0, x0, x, dt );
	advect(0, x, x0, u, v, dt );
	}

	function vel_step(u, v, u0, v0, dt)
	{
	addFields(u, u0, dt );
	addFields(v, v0, dt );
	var temp = u0; u0 = u; u = temp;
	var temp = v0; v0 = v; v = temp;
	diffuse2(u,u0,v,v0, dt);
	project(u, v, u0, v0);
	var temp = u0; u0 = u; u = temp;
	var temp = v0; v0 = v; v = temp;
	advect(1, u, u0, u0, v0, dt);
	advect(2, v, v0, u0, v0, dt);
	project(u, v, u0, v0 );
	}
	var uiCallback = function(d,u,v) {};

	function Field(dens, u, v) {
	// Just exposing the fields here rather than using accessors is a measurable win during display (maybe 5%)
	// but makes the code ugly.
	this.setDensity = function(x, y, d) {
	dens[(x + 1) + (y + 1) * rowSize] = d;
	}
	this.getDensity = function(x, y) {
	return dens[(x + 1) + (y + 1) * rowSize];
	}
	this.setVelocity = function(x, y, xv, yv) {
	u[(x + 1) + (y + 1) * rowSize] = xv;
	v[(x + 1) + (y + 1) * rowSize] = yv;
	}
	this.getXVelocity = function(x, y) {
	return u[(x + 1) + (y + 1) * rowSize];
	}
	this.getYVelocity = function(x, y) {
	return v[(x + 1) + (y + 1) * rowSize];
	}
	this.width = function() { return width; }
	this.height = function() { return height; }
	}
	function queryUI(d, u, v)
	{
	for (var i = 0; i < size; i++)
	u[i] = v[i] = d[i] = 0.0;
	uiCallback(new Field(d, u, v));
	}

	this.update = function () {
	queryUI(dens_prev, u_prev, v_prev);
	vel_step(u, v, u_prev, v_prev, dt);
	dens_step(dens, dens_prev, u, v, dt);
	displayFunc(new Field(dens, u, v));
	}
	this.setDisplayFunction = function(func) {
	displayFunc = func;
	}

	this.iterations = function() { return iterations; }
	this.setIterations = function(iters) {
	if (iters > 0 && iters <= 100)
	iterations = iters;
	}
	this.setUICallback = function(callback) {
	uiCallback = callback;
	}
	var iterations = 10;
	var visc = 0.5;
	var dt = 0.1;
	var dens;
	var dens_prev;
	var u;
	var u_prev;
	var v;
	var v_prev;
	var width;
	var height;
	var rowSize;
	var size;
	var displayFunc;
	function reset()
	{
	rowSize = width + 2;
	size = (width+2)*(height+2);
	dens = new Array(size);
	dens_prev = new Array(size);
	u = new Array(size);
	u_prev = new Array(size);
	v = new Array(size);
	v_prev = new Array(size);
	for (var i = 0; i < size; i++)
	dens_prev[i] = u_prev[i] = v_prev[i] = dens[i] = u[i] = v[i] = 0;
	}
	this.reset = reset;
	this.setResolution = function (hRes, wRes)
	{
	var res = wRes * hRes;
	if (res > 0 && res < 1000000 && (wRes != width \|\| hRes != height)) {
	width = wRes;
	height = hRes;
	reset();
	return true;
	}
	return false;
	}
	this.setResolution(64, 64);
	}