ISEARCH - Revision history

Schlipf at 07:33, 5 March 2026

2026-03-05T07:33:16Z

← Older revision		Revision as of 07:33, 5 March 2026
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	{{NB\|mind\|{{TAG\|ISEARCH\|0}} should only be used for backward compatibility or benchmarking against legacy behavior.}}		{{NB\|mind\|{{TAG\|ISEARCH\|0}} should only be used for backward compatibility or benchmarking against legacy behavior.}}

	== Improved line-search algorithm ==		== Improved line-search algorithm (ISEARCH = 1) ==

	The improved algorithm ~~({{TAG\|ISEARCH\|1}})~~ introduces several enhancements over the legacy implementation:		The improved algorithm introduces several technical enhancements over the legacy implementation to ensure more robust convergence:
	*'''Absolute ~~reference~~''' ~~- each~~ line search step ~~starts~~ from the origin of the search direction rather than progressing incrementally. This ~~improves~~ energy consistency.
	*'''~~Efficient slot system~~''' ~~- all trial~~ steps are ~~stored~~ in ~~slots, reducing~~ redundant ~~energy~~ evaluations.		* '''Absolute Reference''': Each line search step is calculated from the origin of the search direction rather than progressing incrementally. This maintains energy consistency and reduces cumulative rounding errors.
	*'''Minimum-acceptance criterion''' - the ~~final energy~~ minimum of the ~~line search is accepted only if its neighboring slots have also been evaluated (first principles energies are known), ensuring reliable interpolation~~.		* '''Intelligent Slot System''': Trial steps are managed through a "slot-in" mechanism. This system avoids redundant evaluations and strategically places new probes near the predicted minimum to provide the curvature data needed for higher-order fits.
	*'''~~Polynomial and spline fitting~~'''		* '''Adaptive Fitting Logic''': The algorithm scales complexity based on the data density:
	**If ≤ 5 ~~data~~ points ~~are available, an up to~~ 4th-order polynomial fit is ~~used to determine~~ the ~~minimum~~.		** ''Low density (≤ 5 points)'': Uses a combined Harmonic (2nd-order) and 4th-order polynomial fit. The 4th-order result is only accepted if it is consistent with the harmonic direction.
	**If > 5 ~~data~~ points ~~are available~~, ~~a spline interpolation~~ is ~~used instead, offering greater robustness than higher~~-order polynomials.		** ''High density (> 5 points)'': Employs Cubic Spline interpolation, which is more robust against the oscillations often found in high-order polynomials.
	*'''Gradient ~~correction~~''' ~~- the line search typically relies on total~~ energy ~~evaluations only~~, ~~which is faster than computing gradients~~. If the new ~~gradient is not sufficiently orthogonal~~ to the ~~search direction from the previous~~ step, a ~~correction~~ is ~~applied using all available data points~~ (~~via polynomial or spline~~ fit).		* '''Hybrid Gradient-Energy Correction''': While primarily using energy, the algorithm monitors the slope. If the slope at the new point suggests the minimum was missed, it applies a Harmonic Correction to rescale the step length before attempting a polynomial fit.
			* '''Concave Safety Descent''': If the second derivative of the fit is negative (indicating a "hill" rather than a "valley"), the algorithm ignores the fit and automatically reverts to the step that yielded the lowest energy evaluation recorded in the current search.

	== Related tags and articles ==		== Related tags and articles ==

Singraber at 08:12, 24 October 2025

2025-10-24T08:12:00Z

← Older revision		Revision as of 08:12, 24 October 2025
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	{{TAGDEF\|ISEARCH\|0 {{!}} 1\|0}}		{{TAGDEF\|ISEARCH\|0 {{!}} 1\|0}}

	Description: Controls the line-search algorithm used during the direct minimization of the electronic structure ({{~~TAGO~~\|ALGO\|All}}).		Description: Controls the line-search algorithm used during the direct minimization of the electronic structure ({{TAG\|ALGO\|All}}).
	----		----
	*{{~~TAGO~~\|ISEARCH\|0}}: Legacy line-search algorithm.		*{{TAG\|ISEARCH\|0}}: Legacy line-search algorithm.
	*{{~~TAGO~~\|ISEARCH\|1}}: Improved line-search algorithm.		*{{TAG\|ISEARCH\|1}}: Improved line-search algorithm.

	The line search determines the optimal step size along the conjugate gradient search direction. {{~~TAGO~~\|ISEARCH\|0}} performs incremental steps along the search direction. It may lead to inconsistencies in total energy evaluations and slower convergence. {{~~TAGO~~\|ISEARCH\|1}} introduces a more robust and consistent method for determining the optimal step size, leading to improved convergence behavior and more reliable energy minimization.		The line search determines the optimal step size along the conjugate gradient search direction. {{TAG\|ISEARCH\|0}} performs incremental steps along the search direction. It may lead to inconsistencies in total energy evaluations and slower convergence. {{TAG\|ISEARCH\|1}} introduces a more robust and consistent method for determining the optimal step size, leading to improved convergence behavior and more reliable energy minimization.
	{{NB\|important\|We recommend {{~~TAGO~~\|ISEARCH\|1}} when performing electronic minimizations with <code>{{~~TAGO~~\|ALGO}} {{=}} All</code>, as it generally improves convergence stability and reduces the total number of required SCF steps.}}		{{NB\|important\|We recommend {{TAG\|ISEARCH\|1}} when performing electronic minimizations with <code>{{TAG\|ALGO}} {{=}} All</code>, as it generally improves convergence stability and reduces the total number of required SCF steps.}}
	{{NB\|mind\|{{~~TAGO~~\|ISEARCH\|0}} should only be used for backward compatibility or benchmarking against legacy behavior.}}		{{NB\|mind\|{{TAG\|ISEARCH\|0}} should only be used for backward compatibility or benchmarking against legacy behavior.}}

	== Improved line-search algorithm ==		== Improved line-search algorithm ==

	The improved algorithm ({{~~TAGO~~\|ISEARCH\|1}}) introduces several enhancements over the legacy implementation:		The improved algorithm ({{TAG\|ISEARCH\|1}}) introduces several enhancements over the legacy implementation:
	*'''Absolute reference''' - each line search step starts from the origin of the search direction rather than progressing incrementally. This improves energy consistency.		*'''Absolute reference''' - each line search step starts from the origin of the search direction rather than progressing incrementally. This improves energy consistency.
	*'''Efficient slot system''' - all trial steps are stored in slots, reducing redundant energy evaluations.		*'''Efficient slot system''' - all trial steps are stored in slots, reducing redundant energy evaluations.

Huebsch at 07:13, 28 May 2025

2025-05-28T07:13:48Z

← Older revision		Revision as of 07:13, 28 May 2025
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	{{TAGDEF\|ISEARCH\|0 {{!}} 1\|0}}		{{TAGDEF\|ISEARCH\|0 {{!}} 1\|0}}

	Description: Controls the line-search algorithm used during the direct minimization of the electronic structure (~~when~~ {{~~TAG~~\|ALGO}} ~~= All~~).		Description: Controls the line-search algorithm used during the direct minimization of the electronic structure ({{TAGO\|ALGO\|All}}).
	----		----
	*{{TAGO\|ISEARCH\|0}}: Legacy line-search algorithm.		*{{TAGO\|ISEARCH\|0}}: Legacy line-search algorithm.

Huebsch at 07:13, 28 May 2025

2025-05-28T07:13:11Z

← Older revision		Revision as of 07:13, 28 May 2025
Line 3:		Line 3:
	Description: Controls the line-search algorithm used during the direct minimization of the electronic structure (when {{TAG\|ALGO}} = All).		Description: Controls the line-search algorithm used during the direct minimization of the electronic structure (when {{TAG\|ALGO}} = All).
	----		----
	*{{~~TAG~~\|ISEARCH}} ~~= 0~~: Legacy line-search algorithm.		*{{TAGO\|ISEARCH\|0}}: Legacy line-search algorithm.
	*{{~~TAG~~\|ISEARCH}} ~~= 1~~: Improved line-search algorithm.		*{{TAGO\|ISEARCH\|1}}: Improved line-search algorithm.

	The line search determines the optimal step size along the conjugate gradient search direction. {{TAGO\|ISEARCH\|0}} performs incremental steps along the search direction. It may lead to inconsistencies in total energy evaluations and slower convergence. {{TAGO\|ISEARCH\|1}} introduces a more robust and consistent method for determining the optimal step size, leading to improved convergence behavior and more reliable energy minimization.		The line search determines the optimal step size along the conjugate gradient search direction. {{TAGO\|ISEARCH\|0}} performs incremental steps along the search direction. It may lead to inconsistencies in total energy evaluations and slower convergence. {{TAGO\|ISEARCH\|1}} introduces a more robust and consistent method for determining the optimal step size, leading to improved convergence behavior and more reliable energy minimization.

Huebsch at 07:08, 28 May 2025

2025-05-28T07:08:26Z

← Older revision		Revision as of 07:08, 28 May 2025
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	{{TAGDEF\|ISEARCH\|0 {{!}} 1\|0}}		{{TAGDEF\|ISEARCH\|0 {{!}} 1\|0}}

	Description: ~~{{TAG\|ISEARCH}} controls~~ the line search algorithm used during the direct minimization of the electronic structure (when {{TAG\|ALGO}} = A).		Description: Controls the line-search algorithm used during the direct minimization of the electronic structure (when {{TAG\|ALGO}} = All).
	----		----
	*{{TAG\|ISEARCH}} = 0: Legacy line search algorithm.		*{{TAG\|ISEARCH}} = 0: Legacy line-search algorithm.
	*{{TAG\|ISEARCH}} = 1: Improved line search algorithm.		*{{TAG\|ISEARCH}} = 1: Improved line-search algorithm.

	The line search determines the optimal step size along the conjugate gradient search direction. ~~<code>~~{{TAGO\|ISEARCH}} ~~= 0</code>~~ performs incremental steps along the search direction. It may lead to inconsistencies in total energy evaluations and slower convergence. ~~<code>~~{{TAGO\|ISEARCH}} ~~= 1</code>~~ introduces a more robust and consistent method for determining the optimal step size, ~~resulting in better~~ convergence behavior and more reliable energy minimization.		The line search determines the optimal step size along the conjugate gradient search direction. {{TAGO\|ISEARCH\|0}} performs incremental steps along the search direction. It may lead to inconsistencies in total energy evaluations and slower convergence. {{TAGO\|ISEARCH\|1}} introduces a more robust and consistent method for determining the optimal step size, leading to improved convergence behavior and more reliable energy minimization.
	{{NB\|important\|~~It is recommended to use <code>~~{{TAGO\|ISEARCH}} ~~{{=}} 1</code>~~ when performing electronic minimizations with <code>{{TAGO\|ALGO}} {{=}} A</code>, as it generally improves convergence stability and reduces the total number of required SCF steps~~, i~~.~~e., <code>ALGO {{=}} A; ISEARCH {{=}} 1 </code>~~}}		{{NB\|important\|We recommend {{TAGO\|ISEARCH\|1}} when performing electronic minimizations with <code>{{TAGO\|ALGO}} {{=}} All</code>, as it generally improves convergence stability and reduces the total number of required SCF steps.}}
	{{NB\|mind\|~~<code>~~{{TAGO\|ISEARCH}} ~~{{=}} 0</code>~~ should only be used for backward compatibility or benchmarking against legacy behavior.}}		{{NB\|mind\|{{TAGO\|ISEARCH\|0}} should only be used for backward compatibility or benchmarking against legacy behavior.}}

	== Improved line search algorithm ==		== Improved line-search algorithm ==

	The improved algorithm (~~enabled with <code>~~{{TAGO\|ISEARCH}} ~~= 1</code>~~) introduces several enhancements over the legacy implementation:		The improved algorithm ({{TAGO\|ISEARCH\|1}}) introduces several enhancements over the legacy implementation:
	*'''Absolute reference''' - each line search step starts from the origin of the search direction rather than progressing incrementally. This improves energy consistency.		*'''Absolute reference''' - each line search step starts from the origin of the search direction rather than progressing incrementally. This improves energy consistency.
	*'''Efficient slot system''' - all trial steps are stored in slots, reducing redundant energy evaluations.		*'''Efficient slot system''' - all trial steps are stored in slots, reducing redundant energy evaluations.
	*'''Minimum acceptance criterion''' - the final energy minimum of the line search is accepted only if its neighboring slots have also been evaluated (first principles energies are known), ensuring reliable interpolation.		*'''Minimum-acceptance criterion''' - the final energy minimum of the line search is accepted only if its neighboring slots have also been evaluated (first principles energies are known), ensuring reliable interpolation.
	*'''Polynomial and spline fitting'''		*'''Polynomial and spline fitting'''
	**If ≤ 5 data points are available, an up to 4th-order polynomial fit is used to determine the minimum.		**If ≤ 5 data points are available, an up to 4th-order polynomial fit is used to determine the minimum.
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	== Related tags and articles ==		== Related tags and articles ==
	{{TAG\|ALGO}}		{{TAG\|ALGO}}

	~~{{sc\|ISEARCH\|Examples\|Examples that use this tag}}~~

	[[Category:INCAR tag]][[Category:Electronic minimization]]		[[Category:INCAR tag]][[Category:Electronic minimization]]

Csheldon at 14:27, 27 May 2025

2025-05-27T14:27:31Z

← Older revision		Revision as of 14:27, 27 May 2025
Line 7:		Line 7:

	The line search determines the optimal step size along the conjugate gradient search direction. <code>{{TAGO\|ISEARCH}} = 0</code> performs incremental steps along the search direction. It may lead to inconsistencies in total energy evaluations and slower convergence. <code>{{TAGO\|ISEARCH}} = 1</code> introduces a more robust and consistent method for determining the optimal step size, resulting in better convergence behavior and more reliable energy minimization.		The line search determines the optimal step size along the conjugate gradient search direction. <code>{{TAGO\|ISEARCH}} = 0</code> performs incremental steps along the search direction. It may lead to inconsistencies in total energy evaluations and slower convergence. <code>{{TAGO\|ISEARCH}} = 1</code> introduces a more robust and consistent method for determining the optimal step size, resulting in better convergence behavior and more reliable energy minimization.
			{{NB\|important\|It is recommended to use <code>{{TAGO\|ISEARCH}} {{=}} 1</code> when performing electronic minimizations with <code>{{TAGO\|ALGO}} {{=}} A</code>, as it generally improves convergence stability and reduces the total number of required SCF steps, i.e., <code>ALGO {{=}} A; ISEARCH {{=}} 1 </code>}}
			{{NB\|mind\|<code>{{TAGO\|ISEARCH}} {{=}} 0</code> should only be used for backward compatibility or benchmarking against legacy behavior.}}

	== ~~Description of the~~ Improved ~~Algorithm~~ ==		== Improved line search algorithm ==

	The improved algorithm (enabled with <code>{{TAGO\|ISEARCH}} = 1</code>) introduces several enhancements over the legacy implementation:		The improved algorithm (enabled with <code>{{TAGO\|ISEARCH}} = 1</code>) introduces several enhancements over the legacy implementation:
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	**If > 5 data points are available, a spline interpolation is used instead, offering greater robustness than higher-order polynomials.		**If > 5 data points are available, a spline interpolation is used instead, offering greater robustness than higher-order polynomials.
	*'''Gradient correction''' - the line search typically relies on total energy evaluations only, which is faster than computing gradients. If the new gradient is not sufficiently orthogonal to the search direction from the previous step, a correction is applied using all available data points (via polynomial or spline fit).		*'''Gradient correction''' - the line search typically relies on total energy evaluations only, which is faster than computing gradients. If the new gradient is not sufficiently orthogonal to the search direction from the previous step, a correction is applied using all available data points (via polynomial or spline fit).

	~~== Recommendations ==~~
	It is recommended to use <code>{{TAGO\|ISEARCH}} = 1</code> when performing electronic minimizations with <code>{{TAGO\|ALGO}} = A</code>, as it generally improves convergence stability and reduces the total number of required SCF steps, e.g.:
	~~ALGO = A; ISEARCH = 1~~
	~~{{NB\|mind\|<code>{{TAGO\|ISEARCH}} {{=}} 0</code> should only be used for backward compatibility or benchmarking against legacy behavior.}}~~

	== Related tags and articles ==		== Related tags and articles ==

Csheldon: /* Recommendations */

2025-05-27T14:22:41Z

Recommendations

← Older revision		Revision as of 14:22, 27 May 2025
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	== Recommendations ==		== Recommendations ==
	It is recommended to use <code>{{TAGO\|ISEARCH}} = 1</code> when performing electronic minimizations with <code>{{TAGO\|ALGO}} = A</code>, as it generally improves convergence stability and reduces the total number of required SCF steps, e.g.:		It is recommended to use <code>{{TAGO\|ISEARCH}} = 1</code> when performing electronic minimizations with <code>{{TAGO\|ALGO}} = A</code>, as it generally improves convergence stability and reduces the total number of required SCF steps, e.g.:

	ALGO = A; ISEARCH = 1		ALGO = A; ISEARCH = 1

	{{NB\|mind\|<code>{{TAGO\|ISEARCH}} {{=}} 0</code> should only be used for backward compatibility or benchmarking against legacy behavior.}}		{{NB\|mind\|<code>{{TAGO\|ISEARCH}} {{=}} 0</code> should only be used for backward compatibility or benchmarking against legacy behavior.}}

Csheldon: /* Recommendations */

2025-05-27T14:22:30Z

Recommendations

← Older revision		Revision as of 14:22, 27 May 2025
Line 24:		Line 24:
	ALGO = A; ISEARCH = 1		ALGO = A; ISEARCH = 1

	{{NB\|~~Mind~~\|<code>{{TAGO\|ISEARCH}} {{=}} 0</code> should only be used for backward compatibility or benchmarking against legacy behavior.}}		{{NB\|mind\|<code>{{TAGO\|ISEARCH}} {{=}} 0</code> should only be used for backward compatibility or benchmarking against legacy behavior.}}

	== Related tags and articles ==		== Related tags and articles ==

Csheldon: /* Recommendations */

2025-05-27T14:22:22Z

Recommendations

← Older revision		Revision as of 14:22, 27 May 2025
Line 24:		Line 24:
	ALGO = A; ISEARCH = 1		ALGO = A; ISEARCH = 1

	<code>{{TAGO\|ISEARCH}} = 0</code> should only be used for backward compatibility or benchmarking against legacy behavior.		{{NB\|Mind\|<code>{{TAGO\|ISEARCH}} {{=}} 0</code> should only be used for backward compatibility or benchmarking against legacy behavior.}}

	== Related tags and articles ==		== Related tags and articles ==

Csheldon at 14:21, 27 May 2025

2025-05-27T14:21:59Z

← Older revision		Revision as of 14:21, 27 May 2025
Line 20:		Line 20:

	== Recommendations ==		== Recommendations ==
	It is recommended to use <code>{{TAGO\|ISEARCH}} = 1</code> when performing electronic minimizations with <code>{{TAGO\|ALGO}} = A</code>, as it generally improves convergence stability and reduces the total number of required SCF steps. ~~<code>{{TAGO\|ISEARCH}} = 0</code> should only be used for backward compatibility or benchmarking against legacy behavior~~.		It is recommended to use <code>{{TAGO\|ISEARCH}} = 1</code> when performing electronic minimizations with <code>{{TAGO\|ALGO}} = A</code>, as it generally improves convergence stability and reduces the total number of required SCF steps, e.g.:

	== ~~Example ==~~		ALGO = A; ISEARCH = 1

	~~ALGO = A~~		<code>{{TAGO\|ISEARCH}} = 0</code> should only be used for backward compatibility or benchmarking against legacy behavior.
	ISEARCH = 1

	== Related tags and articles ==		== Related tags and articles ==

← Older revision		Revision as of 08:12, 24 October 2025
Line 1:		Line 1:
	{{TAGDEF\|ISEARCH\|0 {{!}} 1\|0}}		{{TAGDEF\|ISEARCH\|0 {{!}} 1\|0}}

	Description: Controls the line-search algorithm used during the direct minimization of the electronic structure ({{~~TAGO~~\|ALGO\|All}}).		Description: Controls the line-search algorithm used during the direct minimization of the electronic structure ({{TAG\|ALGO\|All}}).
	----		----
	*{{~~TAGO~~\|ISEARCH\|0}}: Legacy line-search algorithm.		*{{TAG\|ISEARCH\|0}}: Legacy line-search algorithm.
	*{{~~TAGO~~\|ISEARCH\|1}}: Improved line-search algorithm.		*{{TAG\|ISEARCH\|1}}: Improved line-search algorithm.

	The line search determines the optimal step size along the conjugate gradient search direction. {{~~TAGO~~\|ISEARCH\|0}} performs incremental steps along the search direction. It may lead to inconsistencies in total energy evaluations and slower convergence. {{~~TAGO~~\|ISEARCH\|1}} introduces a more robust and consistent method for determining the optimal step size, leading to improved convergence behavior and more reliable energy minimization.		The line search determines the optimal step size along the conjugate gradient search direction. {{TAG\|ISEARCH\|0}} performs incremental steps along the search direction. It may lead to inconsistencies in total energy evaluations and slower convergence. {{TAG\|ISEARCH\|1}} introduces a more robust and consistent method for determining the optimal step size, leading to improved convergence behavior and more reliable energy minimization.
	{{NB\|important\|We recommend {{~~TAGO~~\|ISEARCH\|1}} when performing electronic minimizations with <code>{{~~TAGO~~\|ALGO}} {{=}} All</code>, as it generally improves convergence stability and reduces the total number of required SCF steps.}}		{{NB\|important\|We recommend {{TAG\|ISEARCH\|1}} when performing electronic minimizations with <code>{{TAG\|ALGO}} {{=}} All</code>, as it generally improves convergence stability and reduces the total number of required SCF steps.}}
	{{NB\|mind\|{{~~TAGO~~\|ISEARCH\|0}} should only be used for backward compatibility or benchmarking against legacy behavior.}}		{{NB\|mind\|{{TAG\|ISEARCH\|0}} should only be used for backward compatibility or benchmarking against legacy behavior.}}

	== Improved line-search algorithm ==		== Improved line-search algorithm ==

	The improved algorithm ({{~~TAGO~~\|ISEARCH\|1}}) introduces several enhancements over the legacy implementation:		The improved algorithm ({{TAG\|ISEARCH\|1}}) introduces several enhancements over the legacy implementation:
	*'''Absolute reference''' - each line search step starts from the origin of the search direction rather than progressing incrementally. This improves energy consistency.		*'''Absolute reference''' - each line search step starts from the origin of the search direction rather than progressing incrementally. This improves energy consistency.
	*'''Efficient slot system''' - all trial steps are stored in slots, reducing redundant energy evaluations.		*'''Efficient slot system''' - all trial steps are stored in slots, reducing redundant energy evaluations.

← Older revision		Revision as of 07:13, 28 May 2025
Line 3:		Line 3:
	Description: Controls the line-search algorithm used during the direct minimization of the electronic structure (when {{TAG\|ALGO}} = All).		Description: Controls the line-search algorithm used during the direct minimization of the electronic structure (when {{TAG\|ALGO}} = All).
	----		----
	*{{~~TAG~~\|ISEARCH}} ~~= 0~~: Legacy line-search algorithm.		*{{TAGO\|ISEARCH\|0}}: Legacy line-search algorithm.
	*{{~~TAG~~\|ISEARCH}} ~~= 1~~: Improved line-search algorithm.		*{{TAGO\|ISEARCH\|1}}: Improved line-search algorithm.

	The line search determines the optimal step size along the conjugate gradient search direction. {{TAGO\|ISEARCH\|0}} performs incremental steps along the search direction. It may lead to inconsistencies in total energy evaluations and slower convergence. {{TAGO\|ISEARCH\|1}} introduces a more robust and consistent method for determining the optimal step size, leading to improved convergence behavior and more reliable energy minimization.		The line search determines the optimal step size along the conjugate gradient search direction. {{TAGO\|ISEARCH\|0}} performs incremental steps along the search direction. It may lead to inconsistencies in total energy evaluations and slower convergence. {{TAGO\|ISEARCH\|1}} introduces a more robust and consistent method for determining the optimal step size, leading to improved convergence behavior and more reliable energy minimization.