# DSCREEN

Bulk Data Entry Defines design response screening data.

Refer to Constraint Screening in the User Guide for information regarding screening responses for design constraints.

## Format

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
DSCREEN RTYPE THOLD MAXC

## Alternate Format

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
DSCREEN AUTO LEVEL BUCK

## Example

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
DSCREEN STRESS -0.6 4

## Associated Cards

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
DRESP1 98 SS11 STRESS PSHELL 1 7   1
DRESP1 99 SS11 STRESS PSHELL 2 7   3
DRESP1 100 SS11 STRESS PSHELL 2 7   5

## Definitions

Field Contents SI Unit Example
RTYPE Response type affected by the response screening settings on this definition.

No default (Character) 1

THOLD Normalized threshold value - constraint/objective will not be retained during the current iteration if its normalized value is below THOLD. 4 5

Default = -0.5 (Real < 0.0)

MAXC Maximum number of constraints/objectives to be retained for each region definition and each load case. 5

Default = 20 (Integer > 0)

AUTO Automatic adjustment of screening criteria.

When this is activated, the screening algorithm will seek to retain the least number of responses that are necessary for stable convergence.

Automatic response screening is active by default. It is disabled by the presence of any DSCREEN definition in the input data.

Default = AUTO (AUTO or blank)

LEVEL The automatic response screening has levels 1 through 5, with 1 being the least aggressive (more responses retained) and 5 being the most aggressive (less responses retained).
ON
Turns on automatic screening to level 3.
OFF
The automatic response screening can also be disabled.

Default = 3 or ON (1, 2, 3, 4, 5, ON, or OFF)

BUCK Controls the activation and deactivation of automatic screening adjustments for buckling eigenvalues in optimization.
BUCK (Default)
NOBUCK

For detailed information, refer to the DSCREEN section of Constraint Screening in the User Guide.

1. RTYPE may be any of the RTYPEs allowed on the DRESP1 entry, or EQUA or EXTERNAL or AUTO.
2. RTYPE EQUA refers to DRESP2 definitions. If DRESP2 definitions are given the same region identifier, they should reference similar equations.
3. RTYPE EXTERNAL refers to DRESP3 definitions. If DRESP3 definitions are given the same region identifier, they should reference similar equations.
4. $\varphi$ is the normalized response ${R}_{i}$ (with regard to a particular constraint). If $\varphi$ > THOLD, the response (referenced on the DCONSTR entry) will be retained for this constrain definition. $\varphi$ is calculated with respect to the upper ( ${U}_{i}$ ) and lower ( ${L}_{i}$ ) bounds of the response on this constraint, as:(1)
${\varphi }_{\mathit{Upper}}=\frac{{R}_{i}}{|{U}_{i}|}-\mathit{sign}\left({U}_{i}\right)$
(2)
${\varphi }_{\mathit{Lower}}=\mathit{sign}\left({L}_{i}\right)-\frac{{R}_{i}}{|{L}_{i}|}$

If the response values are initially lower than the upper bounds and move closer towards their upper bounds, they have a higher chance of being retained. All response values above the upper bounds are retained. Similarly, if response values initially higher than the lower bounds move closer towards their lower bounds, the chances of them being retained is higher. All response values below the lower bounds are retained.

Where, $O$ is the normalized response (with regard to a particular objective). If $O$ > THOLD, the response ( ${W}_{i}$ on the DOBJREF entry) will be retained for this objective definition. $O$ is calculated with respect to the reference values ( ${r}_{i}$ on DOBJREF entry) for the corresponding MINMAX or MAXMIN implementations of the objective, as:(3)
${O}_{\mathit{MINMAX}}=\frac{{W}_{i}}{|{r}_{i}|}-\mathit{sign}\left({r}_{i}\right)$
(4)
${O}_{\mathit{MAXMIN}}=\mathit{sign}\left({r}_{i}\right)-\frac{{W}_{i}}{|{r}_{i}|}$

Depending upon the type of objective (MINMAX or MAXMIN) selected, the chances of a response being retained varies.

5. When no DSCREEN definitions are present in the input data, automatic constraint screening is active for all responses. The presence of any DSCREEN definition disables the automatic screening for all response types.
Note: The THOLD and MAXC defaults do not apply for MASS, MASSFRAC, VOLUME, VOLUMEFRAC, or FREQ responses. The screening thresholds for these responses are set to be very high, by default and they are retained for stability purposes. Hence, constraint screening does not influence these responses and the same will be applied even if auto-screening is activated.
6. With automatic screening, the upper bound on the EIGRL card for buckling analysis will be adjusted in order to calculate only the necessary buckling eigenvalues (responses) that are potentially retained in the optimization.
7. This card is represented as an optidscreens in HyperMesh.