Please note that there are two kind of Global Cells (or \fBGCell\fP for short):
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The \fBGCell\fP used by the global router Knik\&.
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The \fBGCell\fP used by the detailed router (\fBKatabatic\fP & Kite)\&. Although the information they hold is obviously related, they are two separate kind of objects\&.
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The area of the design to be routed is divided in a regular grid of rectangular area, the \fBGCellGrid\fP\&. Each rectangular area is a \fBGCell\fP\&.
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The \fBGCell\fP contains the following informations:
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The AutoSegments that begins or ends in it\&. The list of segments is not avalaible directly but through the AutoContacts that are owned by the \fBGCell\fP\&.
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The AutoSegments that go straight \fIthrough\fP it (or \fIover\fP it)\&. Horizontal & Vertical segments are stored in two separeted list\&. Those two lists are sorted by layer depth (the deepest layers first)\&.
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A lot of synthetic information about the density of tracks used in the \fBGCell\fP\&.
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AutoContacts are affected to GCells, the area of the \fBGCell\fP is the one into which the \fBAutoContact\fP is allowed to be placed\&. It is this that way that the respect of the global routing choosen by Knik is enforced\&. See the \fBAutoContact\fP constraint box\&.
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When tracks are aligned with the \fBGCell\fP boundaries they one exactly on the boundary can belong to the \fBGCell\fP on either side of the boundary\&. But we want a clear and mutually exclusive ownership of each \fBGCell\fP area\&. So, we choose that one \fBGCell\fP do not own the topmost and rightmost track\&. And to implement it, we shrink top and right coordinates by the amount of \fBGCell::getTopRightShrink()\fP, which must be less than the track spacing\&.
.SS"Saturation & Density Computation"
At any depth (i\&.e\&. layer), in the preferred routing direction, a \fBGCell\fP can pass a finite length of wire\&. For example on an horizontal preferred layer: \[ WL_{max} = width(GCell) \times Htracks(GCell) \] Then the density, is the ratio between $WL_{max}$ and the actually used wirelength: \[ Wdensity(depth) = \frac{WL_{used}(depth)}{WL_{max}(depth)} \] Normally, the ratio musn't exceed 1\&.0, but the occupied wire length computation, for now, doesn't merge overlapping wires belonging to the same net, so the ratio may be slightly inaccurate\&. Thus in some pathological cases may be greater than 1\&.0 whithout truly been overloaded\&.
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A Cell is considered as \fIsaturated\fP if the overall density is above the saturation ratio given by \fBSession::getSaturateRatio()\fP\&.
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Contact density is calculated as follow: \[ Cont_{density} = \frac{|Contacts|}{Htracks \times Vtracks \times 4} \] It is a ratio over the number of actual contacts in the \fBGCell\fP and the maximal number\&. The maximal number being the product of the number of tracks in both direction and 4 stands for the hardwired number of layers (the depth)\&.
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Should not be hardwired\&.\&.\&. \fITo be corrected in future versions\&.\fP
.SS"Feedthrough Computation"
The feedtrough value is an estimate is of how many complete tracks have been used on a given layer of the \fBGCell\fP\&. It varies between zero and the number of track on the \fBGCell\fP (complete saturation)\&. As an estimate, it doesn't tell you the actual number of free track, but how many you \fImay expect\fP assuming the routing is reasonably well done\&.
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Computation is done as follow: Wire typeEstimated Cost Straight wire (feedthrough) \fB1\&.0\fP Beginning or ending global wire \fB0\&.5\fP Local wire\&. \fB1/3\fP Blockage wire The exact percentage of the track
.SS"Track Computation"
The number of track that can go through a \fBGCell\fP in the horizontal direction is computed as follow: \[ Htracks = \frac{heigth(GCell)}{Vpitch} + 1 \]
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The pitch is assumed to be the same for every layer and is hardwired to 5\&.0 lambda\&.
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This is a bad architectural choice\&. The informations pertaining to routing should be held at Kite level, not be hardwired and the pitch should be made variable with the layer\&.\&.\&. \fITo be corrected in future versions\fP\&.
.SH"GCell Lazy Evaluation"
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To save processing time, the densities are not recomputed every time a segment is modified (added, removed or moved)\&. Instead a lazy evaluation mechanism is used\&. Densities are recomputed each time a density is queried \fIand\fP the lazy evaluation \fInot\fP explicitly disabled (flag NoUpdate)\&.
.SH"GCell Sorting Key"
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In order to perform a lexicographical sort on the tuple $(density(depth),id)$ of a \fBGCell\fP, a specific slave object \fBGCell::Key\fP is introduced\&. It is the density on one specific depth, not the average density\&.
.SH"GCell Desaturation / Layer Assignment"
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In addition to it's geometrical and density functionality, the \fBGCell\fP provides \fIdesaturation\fP capabilities\&. Desaturation is the operation of moving up feedthough \fBAutoSegment\fP from the bottom layers towards the upper ones in order to balance the densities in the different densities\&. Thoses operations provides building blocks for the layer assignment stage which is provided by the Kabatic tool\&.
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Two strategies are avalaibles, moving one global \fBAutoSegment\fP at a time with \fBGCell::stepDesaturate()\fP or, when one \fBAutoSegment\fP is moved up, move up the whole net trunk with \fBGCell::stepNetDesaturate()\fP\&.
.SH"GCell Implantation"
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\fBGCell\fP derives from Hurricane::ExtensionGo to allow a graphical rendering of the routing density\&.
\fBReturns:\fP The \fBGrid\fP of which \fBGCell\fP is part of\&.
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Referenced by GCell::checkEdgeSaturation(), GCell::getDensity(), GCell::getDown(), GCell::getLeft(), GCell::getRight(), GCell::getUp(), and GCell::stepNetDesaturate()\&.
.SS"unsigned int getDepth () const\fC [inline]\fP"
\fBReturns:\fP The depth (i\&.e\&. number of routing layers) of the \fBGCell\fP\&.
.SS"unsigned int getIndex () const\fC [inline]\fP"
\fBReturns:\fP The linear index of the \fBGCell\fP in the \fBGCellGrid\fP vector\&.
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\fBSee also:\fP
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\fBGCellGrid\fP for the meaning of the index\&.
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Referenced by AutoSegment::canMoveUp(), GCell::hasFreeTrack(), and GCell::stepDesaturate()\&.
.SS"unsigned int getRow () const"
\fBReturns:\fP The row of the \fBGCell\fP in the \fBGCellGrid\fP\&.
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References BaseGrid::getRow()\&.
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Referenced by GCell::checkDensity(), and AutoSegment::computeOptimal()\&.
.SS"unsigned int getColumn () const"
\fBReturns:\fP The Column of the \fBGCell\fP in the \fBGCellGrid\fP\&.
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References BaseGrid::getColumn()\&.
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Referenced by GCell::checkDensity(), and AutoSegment::computeOptimal()\&.
.SS"\fBGCell\fP * getLeft () const"
\fBReturns:\fP The left neighbor of the \fBGCell\fP (\fCNULL\fP if it is the leftmost \fBGCell\fP)\&.
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References GCell::getGCellGrid(), and Grid< GCellT >::getGCellLeft()\&.
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Referenced by AutoVertical::canMoveULeft(), and AutoVertical::moveULeft()\&.
.SS"\fBGCell\fP * getRight () const"
\fBReturns:\fP The right neighbor of the \fBGCell\fP (\fCNULL\fP if it is the rightmost \fBGCell\fP)\&.
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References GCell::getGCellGrid(), and Grid< GCellT >::getGCellRight()\&.
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Referenced by AutoHorizontal::_makeDogleg(), AutoHorizontal::_postCreate(), AutoHorizontal::_preDestroy(), AutoHorizontal::canMoveULeft(), AutoHorizontal::canMoveURight(), AutoVertical::canMoveURight(), GCell::checkEdgeSaturation(), AutoHorizontal::getGCells(), AutoSegment::makeDogleg(), AutoHorizontal::moveULeft(), AutoHorizontal::moveURight(), and AutoVertical::moveURight()\&.
.SS"\fBGCell\fP * getUp () const"
\fBReturns:\fP The top neighbor of the \fBGCell\fP (\fCNULL\fP if it is the topmost \fBGCell\fP)\&.
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References GCell::getGCellGrid(), and Grid< GCellT >::getGCellUp()\&.
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Referenced by AutoVertical::_makeDogleg(), AutoVertical::_postCreate(), AutoVertical::_preDestroy(), AutoVertical::canMoveULeft(), AutoHorizontal::canMoveURight(), AutoVertical::canMoveURight(), GCell::checkEdgeSaturation(), AutoVertical::getGCells(), AutoSegment::makeDogleg(), AutoVertical::moveULeft(), AutoHorizontal::moveURight(), and AutoVertical::moveURight()\&.
.SS"\fBGCell\fP * getDown () const"
\fBReturns:\fP The bottom neighbor of the \fBGCell\fP (\fCNULL\fP if it is the bottommost \fBGCell\fP)\&.
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References Grid< GCellT >::getGCellDown(), and GCell::getGCellGrid()\&.
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Referenced by AutoHorizontal::canMoveULeft(), and AutoHorizontal::moveULeft()\&.
\fBReturns:\fP The upper right Y coordinate of the \fBGCell\fP box (top right shrink applied)\&.
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References Box::getYMax()\&.
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Referenced by AutoVertical::_makeDogleg(), AutoSegment::getExtremity(), and AutoContact::setCBYMax()\&.
.SS"\fBInterval\fP getSide (unsigned int direction) const"
\fBReturns:\fP The interval corresponding to the side position of the \fBGCell\fP box, in \fCdirection\fP\&.
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References Box::getXMax(), Box::getXMin(), Box::getYMax(), Box::getYMin(), Katabatic::KbHorizontal, and Katabatic::KbVertical\&.
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Referenced by AutoHorizontal::_canSlacken(), AutoVertical::_canSlacken(), AutoSegment::makeDogleg(), AutoHorizontal::moveULeft(), AutoVertical::moveULeft(), AutoHorizontal::moveURight(), AutoVertical::moveURight(), and AutoSegment::toConstraintAxis()\&.
.SS"float getHCapacity () const"
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\fBReturns:\fP
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The number of track that can go through the \fBGCell\fP in the horizontal direction\&. For a detailed explanation of the computation see \fBTrack Computation\fP\&.
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References Box::getHeight()\&.
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Referenced by GCell::hasFreeTrack(), and GCell::updateDensity()\&.
.SS"float getVCapacity () const"
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\fBReturns:\fP
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The number of track that can go through the \fBGCell\fP in the vertical direction\&. For a detailed explanation of the computation see \fBTrack Computation\fP\&.
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References Box::getWidth()\&.
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Referenced by GCell::hasFreeTrack(), and GCell::updateDensity()\&.
.SS"float getDensity (unsigned int flags = \fC0\fP) const"
\fBReturns:\fP The average density of the \fBGCell\fP, for all the depths\&.
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\fBSaturation & Density Computation\fP, \fBGCell Lazy Evaluation\fP\&.
Referenced by GCell::isAboveDensity(), and GCell::isSaturated()\&.
.SS"float getCDensity (unsigned int flags = \fC0\fP) const\fC [inline]\fP"
\fBReturns:\fP The density of contacts\&.
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\fBSaturation & Density Computation\fP, \fBGCell Lazy Evaluation\fP\&.
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References GCell::isValid(), and GCell::updateDensity()\&.
.SS"float getWDensity (unsigned int depth, unsigned int flags = \fC0\fP) const\fC [inline]\fP"
\fBReturns:\fP The density of wires at \fCdepth\fP\&.
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\fBSaturation & Density Computation\fP, \fBGCell Lazy Evaluation\fP\&.
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References GCell::isValid(), and GCell::updateDensity()\&.
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Referenced by AutoHorizontal::canMoveULeft(), AutoVertical::canMoveULeft(), AutoHorizontal::canMoveURight(), and AutoVertical::canMoveURight()\&.
.SS"\fBDbU::Unit\fP getBlockage (unsigned int depth) const\fC [inline]\fP"
\fBReturns:\fP The total length of blockage wire on layer at \fCdepth\fP\&.
.SS"float getFragmentation (unsigned int depth) const\fC [inline]\fP"
\fBReturns:\fP The longest free fragment size on layer \fCdepth\fP (in percent)\&.
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References GCell::isValid(), and GCell::updateDensity()\&.
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Referenced by AutoSegment::canMoveUp()\&.
.SS"float getFeedthroughs (unsigned int depth) const\fC [inline]\fP"
\fBReturns:\fP The estimate number of \fIoccupied\fP tracks on layer \fCdepth\fP\&.
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\fBSee also:\fP
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\fBFeedthrough Computation\fP
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References GCell::isValid(), and GCell::updateDensity()\&.
.SS"float getGlobalsCount (unsigned int depth) const\fC [inline]\fP"
\fBReturns:\fP The number of global wires that go completly through the \fBGCell\fP at layer \fCdepth\fP\&. This do not includes the global wires that begins or ends in the \fBGCell\fP\&.
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References GCell::isValid(), and GCell::updateDensity()\&.
\fBtrue\fP if the Up/Right edge is over the \fCthreshold\fP\&.
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Check if the number of AutoSegments crossing the Up & Right edges of the \fBGCell\fP exceed \fCthreshold\fP\&. The \fCthresold\fP must be expressed as a percentage of the full capacity of the edges\&. The overload is computed as a whole and not depth by depth\&.
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References GCell::getGCellGrid(), GCellGrid::getHEdgeCapacity(), GCell::getRight(), GCell::getUp(), GCellGrid::getVEdgeCapacity(), AutoSegment::isLocal(), and Session::lookup()\&.
.SS"void addBlockage (unsigned int depth, \fBDbU::Unit\fP length)"
Adds \fClength\fP of wire blockage to layer \fCdepth\fP\&.
Referenced by GCell::checkDensity(), GCell::getCDensity(), GCell::getDensity(), GCell::getFeedthroughs(), GCell::getFragmentation(), GCell::getGlobalsCount(), GCell::getWDensity(), GCell::hasFreeTrack(), GCell::isAboveDensity(), GCell::stepDesaturate(), and GCell::stepNetDesaturate()\&.
.SS"void updateKey (unsigned int depth)\fC [inline]\fP"
Update the \fBGCell\fP key with the new density at layer \fCdepth\fP\&.
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\fBSee also:\fP
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\fBGCell Sorting Key\fP\&.
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References GCell::Key::update()\&.
.SS"bool rpDesaturate (set< \fBNet\fP *> & nets)"
If the number of RoutingPad in the first routing layer exceed the \fBSession::getSaturateRp()\fP threshold, force a desaturation of layer \fCdepth\fP 1 until it is below 0\&.5\&.
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\fBSee also:\fP
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\fBGCell Desaturation / Layer Assignment\fP
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References Session::getRoutingLayer(), GCell::getRoutingPads(), Session::getSaturateRp(), Katabatic::KbForceMove, and GCell::stepDesaturate()\&.
.SS"bool stepDesaturate (unsigned int depth, set< \fBNet\fP *> & globalNets, \fBAutoSegment\fP *& moved, unsigned int flags = \fC0\fP)"
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\fBParameters:\fP
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\fIdepth\fP The depth to desaturate\&.
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\fIglobalNets\fP The set of Nets of which at least one segment has been moved up\&.
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\fImoved\fP The moved up \fBAutoSegment\fP\&.
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\fIflags\fP If KbForceMove is set, force one \fBAutoSegment\fP to move up, event if the \fBGCell\fP is not saturated in the relevant depth\&.
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\fBReturns:\fP\fBtrue\fP if an \fBAutoSegment\fP has actually been moved up\&.
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Perform the atomic desaturation, that is move up one \fBAutoSegment\fP from layer \fCdepth\fP to layer \fCdepth+2\fP, longuests AutoSegments are moved first\&. Only global feedthrough AutoSegments are candidates to be moved up\&. The Net owning the moved up segment is added to the \fCglobalNets\fP set\&. If the \fBGCell\fP is not saturated on layer \fCdepth\fP, nothing is done\&. If the \fCforced\fP flag is set, one global \fBAutoSegment\fP is moved up regardless of the saturation status\&.
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\fBSee also:\fP
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\fBGCell Desaturation / Layer Assignment\fP
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References GCell::getIndex(), RoutingGauge::getLayerDepth(), Session::getRoutingGauge(), GCell::isSaturated(), Katabatic::KbForceMove, Katabatic::KbHorizontal, Katabatic::KbVertical, and GCell::updateDensity()\&.
\fIglobalNets\fP The set of Nets of which at least one segment has been moved up\&.
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\fIinvalidateds\fP The set of \fBGCell\fP ids that have been invalidateds\&.
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\fBReturns:\fP\fBtrue\fP if a Net has been moved up\&.
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Perform a desaturation by whole Net trunk\&. Select the longest feedthrough \fBAutoSegment\fP in layer \fCdepth\fP, then attempt to move up the whole Net (all it's global AutoSegments are moved up)\&.
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\fBSee also:\fP
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\fBGCell Desaturation / Layer Assignment\fP
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References GCell::getGCellGrid(), RoutingGauge::getLayerDepth(), Session::getRoutingGauge(), Katabatic::KbHorizontal, Katabatic::KbVertical, and GCell::updateDensity()\&.
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Generated automatically by Doxygen for Katabatic - Routing Toolbox from the source code\&.
