//
// Math.NET Numerics, part of the Math.NET Project
// http://numerics.mathdotnet.com
// http://github.com/mathnet/mathnet-numerics
//
// Copyright (c) 2009-2013 Math.NET
//
// 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.
//
using System;
using System.Linq;
using System.Numerics;
namespace IStation.Numerics.Integration
{
///
/// Analytic integration algorithm for smooth functions with no discontinuities
/// or derivative discontinuities and no poles inside the interval.
///
public static class DoubleExponentialTransformation
{
///
/// Maximum number of iterations, until the asked
/// maximum error is (likely to be) satisfied.
///
const int NumberOfMaximumLevels = 10;
///
/// Approximate the integral by the double exponential transformation
///
/// The analytic smooth function to integrate.
/// Where the interval starts, inclusive and finite.
/// Where the interval stops, inclusive and finite.
/// The expected relative accuracy of the approximation.
/// Approximation of the finite integral in the given interval.
public static double Integrate(Func f, double intervalBegin, double intervalEnd, double targetRelativeError)
{
return NewtonCotesTrapeziumRule.IntegrateAdaptiveTransformedOdd(
f,
intervalBegin, intervalEnd,
Enumerable.Range(0, NumberOfMaximumLevels).Select(EvaluateAbcissas),
Enumerable.Range(0, NumberOfMaximumLevels).Select(EvaluateWeights),
1.0,
targetRelativeError);
}
///
/// Approximate the integral by the double exponential transformation
///
/// The analytic smooth complex function to integrate, defined on the real domain.
/// Where the interval starts, inclusive and finite.
/// Where the interval stops, inclusive and finite.
/// The expected relative accuracy of the approximation.
/// Approximation of the finite integral in the given interval.
public static Complex ContourIntegrate(Func f, double intervalBegin, double intervalEnd, double targetRelativeError)
{
return NewtonCotesTrapeziumRule.ContourIntegrateAdaptiveTransformedOdd(
f,
intervalBegin, intervalEnd,
Enumerable.Range(0, NumberOfMaximumLevels).Select(EvaluateAbcissas),
Enumerable.Range(0, NumberOfMaximumLevels).Select(EvaluateWeights),
1.0,
targetRelativeError);
}
///
/// Compute the abscissa vector for a single level.
///
/// The level to evaluate the abscissa vector for.
/// Abscissa Vector.
static double[] EvaluateAbcissas(int level)
{
if (level < PrecomputedAbscissas.Length)
{
return PrecomputedAbscissas[level];
}
double step = level <= 1 ? 1.0 : (1.0/(2 << (level - 2)));
double offset = level == 0 ? 0.0 : (1.0/(2 << (level - 1)));
int length = level == 0 ? 4 : (3 << (level - 1));
double t = 0;
var abcissas = new double[length];
for (int i = 0; i < abcissas.Length; i++)
{
double arg = offset + t;
t += step;
abcissas[i] = Math.Tanh(Constants.PiOver2*Math.Sinh(arg));
}
return abcissas;
}
///
/// Compute the weight vector for a single level.
///
/// The level to evaluate the weight vector for.
/// Weight Vector.
static double[] EvaluateWeights(int level)
{
if (level < PrecomputedWeights.Length)
{
return PrecomputedWeights[level];
}
double step = level <= 1 ? 1.0 : (1.0/(2 << (level - 2)));
double offset = level == 0 ? 0.0 : (1.0/(2 << (level - 1)));
int length = level == 0 ? 4 : (3 << (level - 1));
double t = 0;
var weights = new double[length];
for (int i = 0; i < weights.Length; i++)
{
double arg = offset + t;
t += step;
// TODO: reuse abscissas as computed in EvaluateAbcissas
double abcissa = Math.Tanh(Constants.PiOver2*Math.Sinh(arg));
weights[i] = Constants.PiOver2*(1 - (abcissa*abcissa))*Math.Cosh(arg);
}
return weights;
}
#region Precomputed Abscissas and Weights
///
/// Precomputed abscissa vector per level.
///
static readonly double[][] PrecomputedAbscissas =
{
new[]
{
0.00000000000000000000,
0.95136796407274694574,
0.99997747719246159286,
0.99999999999995705839
},
new[]
{
0.67427149224843582608,
0.99751485645722438683,
0.99999998887566488198
},
new[]
{
0.37720973816403417379,
0.85956905868989663517,
0.98704056050737689169,
0.99968826402835320905,
0.99999920473711471266,
0.99999999995285644818
},
new[]
{
0.19435700332493543161,
0.53914670538796776905,
0.78060743898320029925,
0.91487926326457461091,
0.97396686819567744856,
0.99405550663140214329,
0.99906519645578584642,
0.99990938469514399984,
0.99999531604122052843,
0.99999989278161241838,
0.99999999914270509218,
0.99999999999823216531
},
new[]
{
0.097923885287832333262,
0.28787993274271591456,
0.46125354393958570440,
0.61027365750063894488,
0.73101803479256151149,
0.82331700550640237006,
0.88989140278426019808,
0.93516085752198468323,
0.96411216422354729193,
0.98145482667733517003,
0.99112699244169880223,
0.99610866543750854254,
0.99845420876769773751,
0.99945143443527460584,
0.99982882207287494166,
0.99995387100562796075,
0.99998948201481850361,
0.99999801714059543208,
0.99999969889415261122,
0.99999996423908091534,
0.99999999678719909830,
0.99999999978973286224,
0.99999999999039393352,
0.99999999999970809734
},
new[]
{
0.049055967305077886315,
0.14641798429058794053,
0.24156631953888365838,
0.33314226457763809244,
0.41995211127844715849,
0.50101338937930910152,
0.57558449063515165995,
0.64317675898520470128,
0.70355000514714201566,
0.75669390863372994941,
0.80279874134324126576,
0.84221924635075686382,
0.87543539763040867837,
0.90301328151357387064,
0.92556863406861266645,
0.94373478605275715685,
0.95813602271021369012,
0.96936673289691733517,
0.97797623518666497298,
0.98445883116743083087,
0.98924843109013389601,
0.99271699719682728538,
0.99517602615532735426,
0.99688031812819187372,
0.99803333631543375402,
0.99879353429880589929,
0.99928111192179195541,
0.99958475035151758732,
0.99976797159956083506,
0.99987486504878034648,
0.99993501992508242369,
0.99996759306794345976,
0.99998451990227082442,
0.99999293787666288565,
0.99999693244919035751,
0.99999873547186590954,
0.99999950700571943689,
0.99999981889371276701,
0.99999993755407837378,
0.99999997987450320175,
0.99999999396413420165,
0.99999999832336194826,
0.99999999957078777261,
0.99999999989927772326,
0.99999999997845533741,
0.99999999999582460688,
0.99999999999927152627,
0.99999999999988636130
},
new[]
{
0.024539763574649160379,
0.073525122985671294475,
0.12222912220155764235,
0.17046797238201051811,
0.21806347346971200463,
0.26484507658344795046,
0.31065178055284596083,
0.35533382516507453330,
0.39875415046723775644,
0.44078959903390086627,
0.48133184611690504422,
0.52028805069123015958,
0.55758122826077823080,
0.59315035359195315880,
0.62695020805104287950,
0.65895099174335012438,
0.68913772506166767176,
0.71750946748732412721,
0.74407838354734739913,
0.76886868676824658459,
0.79191549237614211447,
0.81326360850297385168,
0.83296629391941087564,
0.85108400798784873261,
0.86768317577564598669,
0.88283498824466895513,
0.89661425428007602579,
0.90909831816302043511,
0.92036605303195280235,
0.93049693799715340631,
0.93957022393327475539,
0.94766419061515309734,
0.95485549580502268541,
0.96121861515111640753,
0.96682537031235585284,
0.97174454156548730892,
0.97604156025657673933,
0.97977827580061576265,
0.98301279148110110558,
0.98579936302528343597,
0.98818835380074264243,
0.99022624046752774694,
0.99195566300267761562,
0.99341551316926403900,
0.99464105571251119672,
0.99566407681695316965,
0.99651305464025377317,
0.99721334704346870224,
0.99778739195890653083,
0.99825491617199629344,
0.99863314864067747762,
0.99893703483351217373,
0.99917944893488591716,
0.99937140114093768690,
0.99952223765121720422,
0.99963983134560036519,
0.99973076151980848263,
0.99980048143113838630,
0.99985347277311141171,
0.99989338654759256426,
0.99992317012928932869,
0.99994518061445869309,
0.99996128480785666613,
0.99997294642523223656,
0.99998130127012072679,
0.99998722128200062811,
0.99999136844834487344,
0.99999423962761663478,
0.99999620334716617675,
0.99999752962380516793,
0.99999841381096473542,
0.99999899541068996962,
0.99999937270733536947,
0.99999961398855024275,
0.99999976602333243312,
0.99999986037121459941,
0.99999991800479471056,
0.99999995264266446185,
0.99999997311323594362,
0.99999998500307631173,
0.99999999178645609907,
0.99999999558563361584,
0.99999999767323673790,
0.99999999879798350040,
0.99999999939177687583,
0.99999999969875436925,
0.99999999985405611550,
0.99999999993088839501,
0.99999999996803321674,
0.99999999998556879008,
0.99999999999364632387,
0.99999999999727404948,
0.99999999999886126543,
0.99999999999953722654,
0.99999999999981720098,
0.99999999999992987953
}
};
///
/// Precomputed weight vector per level.
///
static readonly double[][] PrecomputedWeights =
{
new[]
{
1.5707963267948966192,
0.230022394514788685,
0.00026620051375271690866,
1.3581784274539090834e-12
},
new[]
{
0.96597657941230114801,
0.018343166989927842087,
2.1431204556943039358e-7
},
new[]
{
1.3896147592472563229,
0.53107827542805397476,
0.076385743570832304188,
0.0029025177479013135936,
0.000011983701363170720047,
1.1631165814255782766e-9
},
new[]
{
1.5232837186347052132,
1.1934630258491569639,
0.73743784836154784136,
0.36046141846934367417,
0.13742210773316772341,
0.039175005493600779072,
0.0077426010260642407123,
0.00094994680428346871691,
0.000062482559240744082891,
1.8263320593710659699e-6,
1.8687282268736410132e-8,
4.9378538776631926964e-11
},
new[]
{
1.5587733555333301451,
1.466014426716965781,
1.297475750424977998,
1.0816349854900704074,
0.85017285645662006895,
0.63040513516474369106,
0.44083323627385823707,
0.290240679312454185,
0.17932441211072829296,
0.10343215422333290062,
0.055289683742240583845,
0.027133510013712003219,
0.012083543599157953493,
0.0048162981439284630173,
0.0016908739981426396472,
0.00051339382406790336017,
0.00013205234125609974879,
0.000028110164327940134749,
4.8237182032615502124e-6,
6.4777566035929719908e-7,
6.5835185127183396672e-8,
4.8760060974240625869e-9,
2.5216347918530148572e-10,
8.6759314149796046502e-12
},
new[]
{
1.5677814313072218572,
1.5438811161769592204,
1.4972262225410362896,
1.4300083548722996676,
1.3452788847662516615,
1.2467012074518577048,
1.1382722433763053734,
1.0240449331118114483,
0.90787937915489531693,
0.79324270082051671787,
0.68306851634426375464,
0.57967810308778764708,
0.48475809121475539287,
0.39938474152571713515,
0.32408253961152890402,
0.258904639514053516,
0.20352399885860174519,
0.15732620348436615027,
0.11949741128869592428,
0.089103139240941462841,
0.065155533432536205042,
0.046668208054846613644,
0.032698732726609031113,
0.022379471063648476483,
0.014937835096050129696,
0.0097072237393916892692,
0.0061300376320830301252,
0.0037542509774318343023,
0.0022250827064786427022,
0.0012733279447082382027,
0.0007018595156842422708,
0.00037166693621677760301,
0.00018856442976700318572,
0.000091390817490710122732,
0.000042183183841757600604,
0.000018481813599879217116,
7.6595758525203162562e-6,
2.9916615878138787094e-6,
1.0968835125901264732e-6,
3.7595411862360630091e-7,
1.1992442782902770219e-7,
3.5434777171421953043e-8,
9.6498888961089633609e-9,
2.4091773256475940779e-9,
5.482835779709497755e-10,
1.1306055347494680536e-10,
2.0989335404511469109e-11,
3.4841937670261059685e-12
},
new[]
{
1.5700420292795931467,
1.5640214037732320999,
1.5520531698454121192,
1.5342817381543034316,
1.5109197230741697127,
1.48224329788553807,
1.4485862549613225916,
1.4103329714462590129,
1.3679105116808964881,
1.3217801174437728579,
1.2724283455378627082,
1.2203581095793582207,
1.1660798699324345766,
1.1101031939653403796,
1.0529288799552666556,
0.99504180404613271514,
0.93690461274566793366,
0.87895234555278212039,
0.82158803526696470334,
0.7651792989089561367,
0.71005590120546898385,
0.65650824613162753076,
0.60478673057840362158,
0.55510187800363350959,
0.5076251588319080997,
0.4624903980553677613,
0.41979566844501548066,
0.37960556938665160999,
0.3419537959230168323,
0.30684590941791694932,
0.27426222968906810637,
0.24416077786983990868,
0.21648020911729617038,
0.19114268413342749532,
0.16805663794826916233,
0.14711941325785693248,
0.12821973363120098675,
0.11123999898874453035,
0.096058391865189467849,
0.082550788110701737654,
0.070592469906866999352,
0.060059642358636300319,
0.05083075757257047107,
0.042787652157725676034,
0.035816505604196436523,
0.029808628117310126969,
0.024661087314753282511,
0.020277183817500123926,
0.016566786254247575375,
0.013446536605285730674,
0.010839937168255907211,
0.0086773307495391815854,
0.0068957859690660035329,
0.0054388997976239984331,
0.0042565295990178580165,
0.0033044669940348302363,
0.0025440657675291729678,
0.0019418357759843675814,
0.0014690143599429791058,
0.0011011261134519383862,
0.00081754101332469493115,
0.00060103987991147422573,
0.00043739495615911687786,
0.00031497209186021200274,
0.00022435965205008549104,
0.00015802788400701191949,
0.00011002112846666697224,
0.000075683996586201477788,
0.000051421497447658802092,
0.0000344921247593431977,
0.000022832118109036146591,
0.000014908514031870608449,
9.5981941283784710776e-6,
6.0899100320949039256e-6,
3.8061983264644899045e-6,
2.3421667208528096843e-6,
1.4183067155493917523e-6,
8.4473756384859863469e-7,
4.9458288702754198508e-7,
2.8449923659159806339e-7,
1.6069394579076224911e-7,
8.9071395140242387124e-8,
4.8420950198072369669e-8,
2.579956822953589238e-8,
1.3464645522302038796e-8,
6.8784610955899001111e-9,
3.4371856744650090511e-9,
1.6788897682161906807e-9,
8.0099784479729665356e-10,
3.7299501843052790038e-10,
1.6939457789411646876e-10,
7.4967397573818224522e-11,
3.230446433325236576e-11,
1.3542512912336274432e-11,
5.5182369468174885821e-12,
2.1835922099233609052e-12
}
};
#endregion
}
}