Codebase list cppad / upstream/2015.00.00.7 doc / ode_taylor.cpp.xml
upstream/2015.00.00.7

Tree @upstream/2015.00.00.7 (Download .tar.gz)

ode_taylor.cpp.xml @upstream/2015.00.00.7 — raw · history · blame 

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
<?xml version='1.0'?>
<html xmlns='http://www.w3.org/1999/xhtml'
      xmlns:math='http://www.w3.org/1998/Math/MathML'
>
<head>
<title>Taylor's Ode Solver: An Example and Test</title>
<meta http-equiv='Content-Type' content='text/html' charset='utf-8'/>
<meta name="description" id="description" content="Taylor's Ode Solver: An Example and Test"/>
<meta name="keywords" id="keywords" content=" taylor's ode solver: an example and test Ode Taylor purpose solution forward mode "/>
<style type='text/css'>
body { color : black }
body { background-color : white }
A:link { color : blue }
A:visited { color : purple }
A:active { color : purple }
</style>
<script type='text/javascript' language='JavaScript' src='_ode_taylor.cpp_xml.js'>
</script>
</head>
<body>
<table><tr>
<td>
<a href="http://www.coin-or.org/CppAD/" target="_top"><img border="0" src="_image.gif"/></a>
</td>
<td><a href="mul_level_adolc_ode.cpp.xml" target="_top">Prev</a>
</td><td><a href="stack_machine.cpp.xml" target="_top">Next</a>
</td><td>
<select onchange='choose_across0(this)'>
<option>Index-&gt;</option>
<option>contents</option>
<option>reference</option>
<option>index</option>
<option>search</option>
<option>external</option>
</select>
</td>
<td>
<select onchange='choose_up0(this)'>
<option>Up-&gt;</option>
<option>CppAD</option>
<option>Example</option>
<option>General</option>
<option>ode_taylor.cpp</option>
</select>
</td>
<td>
<select onchange='choose_down3(this)'>
<option>CppAD-&gt;</option>
<option>Install</option>
<option>Introduction</option>
<option>AD</option>
<option>ADFun</option>
<option>preprocessor</option>
<option>multi_thread</option>
<option>library</option>
<option>ipopt_solve</option>
<option>Example</option>
<option>speed</option>
<option>Appendix</option>
</select>
</td>
<td>
<select onchange='choose_down2(this)'>
<option>Example-&gt;</option>
<option>General</option>
<option>ExampleUtility</option>
<option>ListAllExamples</option>
<option>testvector</option>
</select>
</td>
<td>
<select onchange='choose_down1(this)'>
<option>General-&gt;</option>
<option>ad_fun.cpp</option>
<option>ad_in_c.cpp</option>
<option>conj_grad.cpp</option>
<option>cppad_eigen.hpp</option>
<option>hes_minor_det.cpp</option>
<option>hes_lu_det.cpp</option>
<option>interface2c.cpp</option>
<option>jac_minor_det.cpp</option>
<option>jac_lu_det.cpp</option>
<option>mul_level</option>
<option>ode_stiff.cpp</option>
<option>mul_level_ode.cpp</option>
<option>mul_level_adolc_ode.cpp</option>
<option>ode_taylor.cpp</option>
<option>stack_machine.cpp</option>
</select>
</td>
<td>ode_taylor.cpp</td>
<td>
<select onchange='choose_current0(this)'>
<option>Headings-&gt;</option>
<option>Purpose</option>
<option>ODE</option>
<option>ODE Solution</option>
<option>Forward Mode</option>
</select>
</td>
</tr></table><br/>



<center><b><big><big>Taylor's Ode Solver: An Example and Test</big></big></b></center>
<br/>
<b><big><a name="Purpose" id="Purpose">Purpose</a></big></b>
<br/>
This example solves an ordinary differential equation using Taylor's method;
i.e.,

<math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><mrow>
<mi mathvariant='italic'>Z</mi>
<mo stretchy="false">(</mo>
<mi mathvariant='italic'>t</mi>
<mo stretchy="false">+</mo>
<mi mathvariant='normal'>&#x00394;</mi>
<mi mathvariant='italic'>t</mi>
<mo stretchy="false">)</mo>
<mo stretchy="false">&#x02248;</mo>
<msup><mi mathvariant='italic'>Z</mi>
<mrow><mo stretchy="false">(</mo>
<mn>0</mn>
<mo stretchy="false">)</mo>
</mrow>
</msup>
<mo stretchy="false">(</mo>
<mi mathvariant='italic'>t</mi>
<mo stretchy="false">)</mo>
<mo stretchy="false">+</mo>
<mfrac><mrow><msup><mi mathvariant='italic'>Z</mi>
<mrow><mo stretchy="false">(</mo>
<mn>1</mn>
<mo stretchy="false">)</mo>
</mrow>
</msup>
<mo stretchy="false">(</mo>
<mi mathvariant='italic'>t</mi>
<mo stretchy="false">)</mo>
</mrow>
<mrow><mn>1</mn>
<mo stretchy="false">!</mo>
</mrow>
</mfrac>
<mi mathvariant='normal'>&#x00394;</mi>
<mi mathvariant='italic'>t</mi>
<mo stretchy="false">+</mo>
<mo stretchy="false">&#x022EF;</mo>
<mo stretchy="false">+</mo>
<mfrac><mrow><msup><mi mathvariant='italic'>Z</mi>
<mrow><mo stretchy="false">(</mo>
<mi mathvariant='italic'>p</mi>
<mo stretchy="false">)</mo>
</mrow>
</msup>
<mo stretchy="false">(</mo>
<mi mathvariant='italic'>t</mi>
<mo stretchy="false">)</mo>
</mrow>
<mrow><mi mathvariant='italic'>p</mi>
<mo stretchy="false">!</mo>
</mrow>
</mfrac>
<mo stretchy="false">(</mo>
<mi mathvariant='normal'>&#x00394;</mi>
<mi mathvariant='italic'>t</mi>
<msup><mo stretchy="false">)</mo>
<mi mathvariant='italic'>p</mi>
</msup>
<mo stretchy="false">)</mo>
</mrow></math>

<br/>
<b><big><a name="ODE" id="ODE">ODE</a></big></b>
<br/>
The ODE is defined by the function

<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow>
<mi mathvariant='italic'>h</mi>
<mo stretchy="false">:</mo>
<msup><mrow><mstyle mathvariant='bold'><mi mathvariant='bold'>R</mi>
</mstyle></mrow>
<mi mathvariant='italic'>n</mi>
</msup>
<mo stretchy="false">&#x02192;</mo>
<msup><mrow><mstyle mathvariant='bold'><mi mathvariant='bold'>R</mi>
</mstyle></mrow>
<mi mathvariant='italic'>n</mi>
</msup>
</mrow></math>

,
which for this example is given by 

<math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><mrow>
<msup><mi mathvariant='italic'>Z</mi>
<mrow><mo stretchy="false">(</mo>
<mn>1</mn>
<mo stretchy="false">)</mo>
</mrow>
</msup>
<mo stretchy="false">(</mo>
<mi mathvariant='italic'>t</mi>
<mo stretchy="false">)</mo>
<mo stretchy="false">=</mo>
<mi mathvariant='italic'>H</mi>
<mo stretchy="false">[</mo>
<mi mathvariant='italic'>Z</mi>
<mo stretchy="false">(</mo>
<mi mathvariant='italic'>t</mi>
<mo stretchy="false">)</mo>
<mo stretchy="false">]</mo>
<mo stretchy="false">=</mo>
<mrow><mo stretchy="true">(</mo><mrow><mtable rowalign="center" ><mtr><mtd columnalign="center" >
<mn>1</mn>
</mtd></mtr><mtr><mtd columnalign="center" >
<msub><mi mathvariant='italic'>Z</mi>
<mn>1</mn>
</msub>
<mo stretchy="false">(</mo>
<mi mathvariant='italic'>t</mi>
<mo stretchy="false">)</mo>
</mtd></mtr><mtr><mtd columnalign="center" >
<mo stretchy="false">&#x022EE;</mo>
</mtd></mtr><mtr><mtd columnalign="center" >
<msub><mi mathvariant='italic'>Z</mi>
<mrow><mi mathvariant='italic'>n</mi>
<mn>-1</mn>
</mrow>
</msub>
<mo stretchy="false">(</mo>
<mi mathvariant='italic'>t</mi>
<mo stretchy="false">)</mo>
</mtd></mtr></mtable>
</mrow><mo stretchy="true">)</mo></mrow>
</mrow></math>

and the initial condition is 
<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow>
<mi mathvariant='italic'>z</mi>
<mo stretchy="false">(</mo>
<mn>0</mn>
<mo stretchy="false">)</mo>
<mo stretchy="false">=</mo>
<mn>0</mn>
</mrow></math>

.

<br/>
<br/>
<b><big><a name="ODE Solution" id="ODE Solution">ODE Solution</a></big></b>
<br/>
The solution for this example can be calculated by 
starting with the first row and then using the solution
for the first row to solve the second and so on.
Doing this we obtain

<math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><mrow>
<mi mathvariant='italic'>Z</mi>
<mo stretchy="false">(</mo>
<mi mathvariant='italic'>t</mi>
<mo stretchy="false">)</mo>
<mo stretchy="false">=</mo>
<mrow><mo stretchy="true">(</mo><mrow><mtable rowalign="center" ><mtr><mtd columnalign="center" >
<mi mathvariant='italic'>t</mi>
</mtd></mtr><mtr><mtd columnalign="center" >
<msup><mi mathvariant='italic'>t</mi>
<mn>2</mn>
</msup>
<mo stretchy="false">/</mo>
<mn>2</mn>
</mtd></mtr><mtr><mtd columnalign="center" >
<mo stretchy="false">&#x022EE;</mo>
</mtd></mtr><mtr><mtd columnalign="center" >
<msup><mi mathvariant='italic'>t</mi>
<mi mathvariant='italic'>n</mi>
</msup>
<mo stretchy="false">/</mo>
<mi mathvariant='italic'>n</mi>
<mo stretchy="false">!</mo>
</mtd></mtr></mtable>
</mrow><mo stretchy="true">)</mo></mrow>
</mrow></math>

<br/>
<b><big><a name="Forward Mode" id="Forward Mode">Forward Mode</a></big></b>
<br/>
Given the Taylor coefficients for 
<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow>
<mi mathvariant='italic'>k</mi>
<mo stretchy="false">=</mo>
<mn>0</mn>
<mo stretchy="false">,</mo>
<mo stretchy="false">&#x02026;</mo>
<mo stretchy="false">,</mo>
<mi mathvariant='italic'>K</mi>
</mrow></math>



<math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><mrow>
<msup><mi mathvariant='italic'>z</mi>
<mrow><mo stretchy="false">(</mo>
<mi mathvariant='italic'>k</mi>
<mo stretchy="false">)</mo>
</mrow>
</msup>
<mo stretchy="false">=</mo>
<mfrac><mrow><msup><mi mathvariant='italic'>Z</mi>
<mrow><mo stretchy="false">(</mo>
<mi mathvariant='italic'>k</mi>
<mo stretchy="false">)</mo>
</mrow>
</msup>
</mrow>
<mrow><mi mathvariant='italic'>k</mi>
<mo stretchy="false">!</mo>
</mrow>
</mfrac>
<mo stretchy="false">(</mo>
<mi mathvariant='italic'>t</mi>
<mo stretchy="false">)</mo>
</mrow></math>

we note that

<math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><mrow>
<mtable rowalign="center" ><mtr><mtd columnalign="right" >
<msup><mi mathvariant='italic'>Z</mi>
<mrow><mo stretchy="false">(</mo>
<mn>1</mn>
<mo stretchy="false">)</mo>
</mrow>
</msup>
<mo stretchy="false">(</mo>
<mi mathvariant='italic'>t</mi>
<mo stretchy="false">)</mo>
</mtd><mtd columnalign="center" >
<mo stretchy="false">=</mo>
</mtd><mtd columnalign="left" >
<mi mathvariant='italic'>H</mi>
<mo stretchy="false">(</mo>
<msup><mi mathvariant='italic'>z</mi>
<mrow><mo stretchy="false">(</mo>
<mn>0</mn>
<mo stretchy="false">)</mo>
</mrow>
</msup>
<mo stretchy="false">+</mo>
<msup><mi mathvariant='italic'>z</mi>
<mrow><mo stretchy="false">(</mo>
<mn>1</mn>
<mo stretchy="false">)</mo>
</mrow>
</msup>
<mi mathvariant='italic'>t</mi>
<mo stretchy="false">+</mo>
<mo stretchy="false">&#x022EF;</mo>
<mo stretchy="false">+</mo>
<msup><mi mathvariant='italic'>z</mi>
<mrow><mo stretchy="false">(</mo>
<mi mathvariant='italic'>K</mi>
<mo stretchy="false">)</mo>
</mrow>
</msup>
<msup><mi mathvariant='italic'>t</mi>
<mi mathvariant='italic'>K</mi>
</msup>
<mo stretchy="false">)</mo>
<mo stretchy="false">+</mo>
<mi mathvariant='italic'>O</mi>
<mo stretchy="false">(</mo>
<msup><mi mathvariant='italic'>t</mi>
<mrow><mi mathvariant='italic'>K</mi>
<mo stretchy="false">+</mo>
<mn>1</mn>
</mrow>
</msup>
<mo stretchy="false">)</mo>
</mtd></mtr><mtr><mtd columnalign="right" >
</mtd><mtd columnalign="center" >
<mo stretchy="false">=</mo>
</mtd><mtd columnalign="left" >
<msup><mi mathvariant='italic'>h</mi>
<mrow><mo stretchy="false">(</mo>
<mn>0</mn>
<mo stretchy="false">)</mo>
</mrow>
</msup>
<mo stretchy="false">+</mo>
<msup><mi mathvariant='italic'>h</mi>
<mrow><mo stretchy="false">(</mo>
<mn>1</mn>
<mo stretchy="false">)</mo>
</mrow>
</msup>
<mi mathvariant='italic'>t</mi>
<mo stretchy="false">+</mo>
<mo stretchy="false">&#x022EF;</mo>
<mo stretchy="false">+</mo>
<msup><mi mathvariant='italic'>h</mi>
<mrow><mo stretchy="false">(</mo>
<mi mathvariant='italic'>K</mi>
<mo stretchy="false">)</mo>
</mrow>
</msup>
<msup><mi mathvariant='italic'>t</mi>
<mi mathvariant='italic'>K</mi>
</msup>
<mo stretchy="false">+</mo>
<mi mathvariant='italic'>O</mi>
<mo stretchy="false">(</mo>
<msup><mi mathvariant='italic'>t</mi>
<mrow><mi mathvariant='italic'>K</mi>
<mo stretchy="false">+</mo>
<mn>1</mn>
</mrow>
</msup>
<mo stretchy="false">)</mo>
</mtd></mtr></mtable>
</mrow></math>

where 
<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow>
<msup><mi mathvariant='italic'>h</mi>
<mrow><mo stretchy="false">(</mo>
<mi mathvariant='italic'>k</mi>
<mo stretchy="false">)</mo>
</mrow>
</msup>
</mrow></math>

 is the <code><i>k</i></code>-th order Taylor coefficient for

<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow>
<mi mathvariant='italic'>H</mi>
<mo stretchy="false">(</mo>
<mi mathvariant='italic'>Z</mi>
<mo stretchy="false">(</mo>
<mi mathvariant='italic'>t</mi>
<mo stretchy="false">)</mo>
<mo stretchy="false">)</mo>
</mrow></math>

.
Taking <code><i>K</i></code>-th order derivatives of both sides we obtain

<math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><mrow>
<mtable rowalign="center" ><mtr><mtd columnalign="right" >
<msup><mi mathvariant='italic'>Z</mi>
<mrow><mo stretchy="false">(</mo>
<mi mathvariant='italic'>K</mi>
<mo stretchy="false">+</mo>
<mn>1</mn>
<mo stretchy="false">)</mo>
</mrow>
</msup>
<mo stretchy="false">(</mo>
<mi mathvariant='italic'>t</mi>
<mo stretchy="false">)</mo>
</mtd><mtd columnalign="center" >
<mo stretchy="false">=</mo>
</mtd><mtd columnalign="left" >
<mi mathvariant='italic'>K</mi>
<mo stretchy="false">!</mo>
<msup><mi mathvariant='italic'>h</mi>
<mrow><mo stretchy="false">(</mo>
<mi mathvariant='italic'>K</mi>
<mo stretchy="false">)</mo>
</mrow>
</msup>
</mtd></mtr><mtr><mtd columnalign="right" >
<msup><mi mathvariant='italic'>z</mi>
<mrow><mo stretchy="false">(</mo>
<mi mathvariant='italic'>K</mi>
<mo stretchy="false">+</mo>
<mn>1</mn>
<mo stretchy="false">)</mo>
</mrow>
</msup>
</mtd><mtd columnalign="center" >
<mo stretchy="false">=</mo>
</mtd><mtd columnalign="left" >
<msup><mi mathvariant='italic'>h</mi>
<mrow><mo stretchy="false">(</mo>
<mi mathvariant='italic'>K</mi>
<mo stretchy="false">)</mo>
</mrow>
</msup>
<mo stretchy="false">/</mo>
<mi mathvariant='italic'>K</mi>
</mtd></mtr></mtable>
</mrow></math>

The code below uses this relationship to implement Taylor's
method for approximating the solution of an ODE.

<code><font color="blue">
<pre style='display:inline'> 

# include &lt;cppad/cppad.hpp&gt;

// =========================================================================
// define types for each level
namespace { // BEGIN empty namespace
	using CppAD::AD;

	<a href="testvector.xml" target="_top">CPPAD_TESTVECTOR</a>( <a href="ad.xml" target="_top">AD</a>&lt;double&gt; ) ode(
		const <a href="testvector.xml" target="_top">CPPAD_TESTVECTOR</a>( <a href="ad.xml" target="_top">AD</a>&lt;double&gt; )&amp; Z )
	{	size_t n = Z.size();
		<a href="testvector.xml" target="_top">CPPAD_TESTVECTOR</a>( <a href="ad.xml" target="_top">AD</a>&lt;double&gt; ) y(n);
		y[0] = 1;
		for(size_t k = 1; k &lt; n; k++)
			y[k] = Z[k-1]; 
		return y;
	}

}

// -------------------------------------------------------------------------
// Example that uses Taylor's method to solve ordinary differential equaitons
bool ode_taylor(void)
{	// initialize the return value as true	
	bool ok = true;

	// some temporary indices
	size_t i, j, k;

	// The ODE does not depend on the arugment values
	// so only tape once, also note that ode does not depend on t
	size_t n = 5;    // number of independent and dependent variables
	<a href="testvector.xml" target="_top">CPPAD_TESTVECTOR</a>( <a href="ad.xml" target="_top">AD</a>&lt;double&gt; ) a_x(n), a_y(n);
	CppAD::<a href="independent.xml" target="_top">Independent</a>( a_x );
	a_y = ode(a_x);
	CppAD::<a href="funconstruct.xml" target="_top">ADFun</a>&lt;double&gt; H(a_x, a_y);

	// initialize the solution vector at time zero
	<a href="testvector.xml" target="_top">CPPAD_TESTVECTOR</a>( double ) z(n);
	for(j = 0; j &lt; n; j++)
		z[j] = 0.0; 

	size_t order   = n;   // order of the Taylor method
	size_t n_step  = 4;   // number of time steps
	double dt      = 0.5; // step size in time
	// Taylor coefficients of order k
	<a href="testvector.xml" target="_top">CPPAD_TESTVECTOR</a>( double ) hk(n), zk(n);

	// loop with respect to each step of Taylor's method
	for(size_t i_step = 0; i_step &lt; n_step; i_step++)
	{	// Use Taylor's method to take a step
		zk           = z;     // initialize z^{(k)}  for k = 0
		double dt_kp = dt;    // initialize dt^(k+1) for k = 0
		for(k = 0; k &lt; order; k++)
		{	// evaluate k-th order Taylor coefficient of H
			hk = H.<a href="forward.xml" target="_top">Forward</a>(k, zk);
 
			for(j = 0; j &lt; n; j++)
			{	// convert to (k+1)-Taylor coefficient for z
				zk[j] = hk[j] / double(k + 1);

				// add term for to this Taylor coefficient
				// to solution for y(t, x)
				z[j] += zk[j] * dt_kp;
			}
			// next power of t
			dt_kp *= dt;
		}
	}

	// check solution of the ODE, 
	// Taylor's method should have no truncation error for this case
	double eps   = 100. * std::numeric_limits&lt;double&gt;::epsilon();
	double check = 1.;
	double t     = n_step * dt;
	for(i = 0; i &lt; n; i++)
	{	check *= t / double(i + 1);
		ok &amp;= CppAD::<a href="nearequal.xml" target="_top">NearEqual</a>(z[i], check, eps, eps);
	}

	return ok;
}

</pre>

</font></code>


<hr/>Input File: example/ode_taylor.cpp

</body>
</html>