/// <summary>
/// Adaptive integration on semi-infinite interval (a,+Infinity).
/// </summary>
/// <param name="f">Function to integrate.</param>
/// <param name="a">Lower integration limit.</param>
/// <param name="epsabs">Specifies the expected absolute error of integration. Should be set to zero (0) if you specify a relative error.</param>
/// <param name="epsrel">Specifies the expected relative error of integration. Should be set to zero (0) if you specify an absolute error.</param>
/// <param name="limit">Maximum number of subintervals used for integration.</param>
/// <param name="integrationRule">Integration rule used for integration (only for this function call).</param>
/// <param name="debug">Setting of the debug flag (only for this function call). If the integration fails or the specified accuracy
/// is not reached, an exception is thrown if the debug flag is set to true. If set to false, the return value of the integration
/// function will be set to the appropriate error code (an exception will be thrown then only for serious errors).</param>
/// <param name="result">On return, contains the integration result.</param>
/// <param name="abserr">On return, contains the absolute error of integration.</param>
/// <param name="tempStorage">Provides a temporary storage object that you can reuse for repeating function calls.</param>
/// <returns>Null if successfull, otherwise the appropriate error code.</returns>
public static GSL_ERROR Integration(Func <double, double> f,
double a,
double epsabs, double epsrel,
int limit,
gsl_integration_rule integrationRule, bool debug,
out double result, out double abserr,
ref object tempStorage)
{
var algo = tempStorage as QagiuIntegration;
if (null == algo)
{
tempStorage = algo = new QagiuIntegration(integrationRule, debug);
}
return(algo.Integrate(f, a, epsabs, epsrel, limit, integrationRule, debug, out result, out abserr));
}
Integration(Func <double, double> f,
double a,
double epsabs, double epsrel,
int limit,
out double result, out double abserr,
ref object tempStorage
)
{
var algo = tempStorage as QagiuIntegration;
if (null == algo)
{
tempStorage = algo = new QagiuIntegration();
}
return(algo.Integrate(f, a, epsabs, epsrel, limit, out result, out abserr));
}
Integration(Func<double, double> f,
double a,
double epsabs, double epsrel,
int limit,
out double result, out double abserr,
ref object tempStorage
)
{
QagiuIntegration algo = tempStorage as QagiuIntegration;
if (null == algo)
tempStorage = algo = new QagiuIntegration();
return algo.Integrate(f, a, epsabs, epsrel, limit, out result, out abserr);
}
/// <summary>
/// Adaptive integration on semi-infinite interval (a,+Infinity).
/// </summary>
/// <param name="f">Function to integrate.</param>
/// <param name="a">Lower integration limit.</param>
/// <param name="epsabs">Specifies the expected absolute error of integration. Should be set to zero (0) if you specify a relative error.</param>
/// <param name="epsrel">Specifies the expected relative error of integration. Should be set to zero (0) if you specify an absolute error.</param>
/// <param name="limit">Maximum number of subintervals used for integration.</param>
/// <param name="integrationRule">Integration rule used for integration (only for this function call).</param>
/// <param name="debug">Setting of the debug flag (only for this function call). If the integration fails or the specified accuracy
/// is not reached, an exception is thrown if the debug flag is set to true. If set to false, the return value of the integration
/// function will be set to the appropriate error code (an exception will be thrown then only for serious errors).</param>
/// <param name="result">On return, contains the integration result.</param>
/// <param name="abserr">On return, contains the absolute error of integration.</param>
/// <param name="tempStorage">Provides a temporary storage object that you can reuse for repeating function calls.</param>
/// <returns>Null if successfull, otherwise the appropriate error code.</returns>
public static GSL_ERROR Integration(Func<double, double> f,
double a,
double epsabs, double epsrel,
int limit,
gsl_integration_rule integrationRule, bool debug,
out double result, out double abserr,
ref object tempStorage)
{
QagiuIntegration algo = tempStorage as QagiuIntegration;
if (null == algo)
tempStorage = algo = new QagiuIntegration(integrationRule, debug);
return algo.Integrate(f, a, epsabs, epsrel, limit, integrationRule, debug, out result, out abserr);
}
gsl_integration_qawf(Func <double, double> f,
double a,
double epsabs,
int limit,
gsl_integration_workspace workspace,
gsl_integration_workspace cycle_workspace,
gsl_integration_qawo_table wf,
out double result, out double abserr,
bool bDebug)
{
double area, errsum;
double res_ext, err_ext;
double correc, total_error = 0.0, truncation_error = 0;
int ktmin = 0;
int iteration = 0;
var table = new extrapolation_table();
double cycle;
double omega = wf.omega;
double p = 0.9;
double factor = 1;
double initial_eps, eps;
int error_type = 0;
/* Initialize results */
workspace.initialise(a, a);
result = 0;
abserr = 0;
if (limit > workspace.limit)
{
return(new GSL_ERROR("iteration limit exceeds available workspace", GSL_ERR.GSL_EINVAL, bDebug));
}
/* Test on accuracy */
if (epsabs <= 0)
{
return(new GSL_ERROR("absolute tolerance epsabs must be positive", GSL_ERR.GSL_EBADTOL, bDebug));
}
if (omega == 0.0)
{
if (wf.sine == gsl_integration_qawo_enum.GSL_INTEG_SINE)
{
/* The function sin(w x) f(x) is always zero for w = 0 */
result = 0;
abserr = 0;
return(null); // GSL_SUCCESS;
}
else
{
/* The function cos(w x) f(x) is always f(x) for w = 0 */
GSL_ERROR status = QagiuIntegration.gsl_integration_qagiu(f, a, epsabs, 0.0,
cycle_workspace.limit,
cycle_workspace,
out result, out abserr,
QagiuIntegration.DefaultIntegrationRule, QagiuIntegration.DefaultDebugFlag);
return(status);
}
}
if (epsabs > GSL_CONST.GSL_DBL_MIN / (1 - p))
{
eps = epsabs * (1 - p);
}
else
{
eps = epsabs;
}
initial_eps = eps;
area = 0;
errsum = 0;
res_ext = 0;
err_ext = GSL_CONST.GSL_DBL_MAX;
correc = 0;
cycle = (2 * Math.Floor(Math.Abs(omega)) + 1) * Math.PI / Math.Abs(omega);
wf.set_length(cycle);
table.initialise_table();
for (iteration = 0; iteration < limit; iteration++)
{
double a1 = a + iteration * cycle;
double b1 = a1 + cycle;
double epsabs1 = eps * factor;
GSL_ERROR status = gsl_integration_qawo(f, a1, epsabs1, 0.0, limit,
cycle_workspace, wf,
out var area1, out var error1, false);
workspace.append_interval(a1, b1, area1, error1);
factor *= p;
area = area + area1;
errsum = errsum + error1;
/* estimate the truncation error as 50 times the final term */
truncation_error = 50 * Math.Abs(area1);
total_error = errsum + truncation_error;
if (total_error < epsabs && iteration > 4)
{
goto compute_result;
}
if (error1 > correc)
{
correc = error1;
}
if (null != status)
{
eps = Math.Max(initial_eps, correc * (1.0 - p));
}
if (null != status && total_error < 10 * correc && iteration > 3)
{
goto compute_result;
}
table.append_table(area);
if (table.n < 2)
{
continue;
}
table.qelg(out var reseps, out var erreps);
ktmin++;
if (ktmin >= 15 && err_ext < 0.001 * total_error)
{
error_type = 4;
}
if (erreps < err_ext)
{
ktmin = 0;
err_ext = erreps;
res_ext = reseps;
if (err_ext + 10 * correc <= epsabs)
{
break;
}
if (err_ext <= epsabs && 10 * correc >= epsabs)
{
break;
}
}
}
if (iteration == limit)
{
error_type = 1;
}
if (err_ext == GSL_CONST.GSL_DBL_MAX)
{
goto compute_result;
}
err_ext = err_ext + 10 * correc;
result = res_ext;
abserr = err_ext;
if (error_type == 0)
{
return(null); // GSL_SUCCESS;
}
if (res_ext != 0.0 && area != 0.0)
{
if (err_ext / Math.Abs(res_ext) > errsum / Math.Abs(area))
{
goto compute_result;
}
}
else if (err_ext > errsum)
{
goto compute_result;
}
else if (area == 0.0)
{
goto return_error;
}
if (error_type == 4)
{
err_ext = err_ext + truncation_error;
}
goto return_error;
compute_result:
result = area;
abserr = total_error;
return_error:
if (error_type > 2)
{
error_type--;
}
if (error_type == 0)
{
return(null); // GSL_SUCCESS;
}
else if (error_type == 1)
{
return(new GSL_ERROR("number of iterations was insufficient", GSL_ERR.GSL_EMAXITER, bDebug));
}
else if (error_type == 2)
{
return(new GSL_ERROR("cannot reach tolerance because of roundoff error",
GSL_ERR.GSL_EROUND, bDebug));
}
else if (error_type == 3)
{
return(new GSL_ERROR("bad integrand behavior found in the integration interval",
GSL_ERR.GSL_ESING, bDebug));
}
else if (error_type == 4)
{
return(new GSL_ERROR("roundoff error detected in the extrapolation table",
GSL_ERR.GSL_EROUND, bDebug));
}
else if (error_type == 5)
{
return(new GSL_ERROR("integral is divergent, or slowly convergent",
GSL_ERR.GSL_EDIVERGE, bDebug));
}
else
{
return(new GSL_ERROR("could not integrate function", GSL_ERR.GSL_EFAILED, bDebug));
}
}
