CGT - The Graphical Interface¶

The Coriolis graphical interface is split up into two windows.

The Viewer, with the following features:
- Basic load/save capabilities.
- Display the current working cell. Could be empty if the design is not yet placed.
- Execute Stratus Scripts.
- Menu to run the tools (placement, routage).

Features are detailed in Viewer & Tools.

The Controller, which allows:
- Tweak what is displayer by the Viewer. Through the Look, Filter and Layers&Gos tabs.
- Browse the netlist with eponym tab.
- Show the list of selected objects (if any) with selection
- Walk through the Database, the Cell or the Selection with Inspector. This is an advanced feature, reserved for experimented users.
- The tab Settings which give access to all the settings. They are closely related to Configuration & Initialisation.

Viewer & Tools¶

Stratus Netlist Capture¶

Stratus is the replacement for GenLib procedural netlist capture language. It is designed as a set of Python classes, and comes with it’s own documentation (Stratus Documentation)

The Hurricane Data-Base¶

The Alliance flow is based on the mbk data-base, which has one data-structure for each view. That is, Lofig for the logical view and Phfig for the physical view. The place and route tools were responsible for maintaining (or not) the coherency between views. Reflecting this weak coupling between views, each one was stored in a separate file with a specific format. The logical view is stored in a vst file in vhdl format and the physical in an ap file in an ad-hoc format.

The Coriolis flow is based on the Hurricane data-base, which has a unified structure for logical and physical view. That data structure is the Cell object. The Cell can have any state between pure netlist and completly placed and routed design. Although the memory representation of the views has deeply changed we still use the Alliance files format, but they now really represent views of the same object. The point is that one must be very careful about view coherency when going to and from Coriolis.

As for the second release, Coriolis can be used only for three purposes :

Placing a design, in which case the netlist view must be present.
Routing a design, in that case the netlist view and the layout view must be present and layout view must contain a placement. Both views must have the same name. When saving the routed design, it is advised to change the design name otherwise the original unrouted placement in the layout view will be overwritten.
Viewing a design, the netlist view must be present, if a layout view is present it still must have the same name but it can be in any state.

Synthetizing and loading a design¶

Coriolis supports several file formats. It can load all file format from the Alliance toolchain (.ap for layout, behavioural and structural vhdl .vbe and .vst), BLIF netlist format as well as benchmark formats from the ISPD contests.

It can be compiled with LEF/DEF support, although it requires acceptance of the SI2 license and may not be compiled in your version of the software.

Synthesis under Yosys¶

You can create a BLIF file from the Yosys synthetizer, which can be imported under Coriolis. Most libraries are specified as a .lib liberty file and a .lef LEF file. Yosys opens most .lib files with minor modifications, but LEF support in Coriolis relies on SI2. If Coriolis hasn’t been compiled against it, the library is given in Alliance .ap format. Some free libraries already provide both .ap and .lib files.

Once you have installed a common library under Yosys and Coriolis, just synthetize your design with Yosys and import it (as Blif without the extension) under Coriolis to perform place&route.

Synthesis under Alliance¶

Alliance is an older toolchain but has been extensively used for years. Coriolis can import and write Alliance designs and libraries directly.

Etesian – Placer¶

The Etesian placer is a state of the art (as of 2015) analytical placer. It is within 5% of other placers’ solutions, but is normally a bit worse than ePlace. This Coriolis tool is actually an encapsulation of Coloquinte which is the placer.

Note

Instance Uniquification Unsupported: a same logical instance cannot have two different placements. So, either you manually make a clone of it or you supply a placement for it. We need to implement uniquification in the Hurricane database.

Hierarchical Placement

The placement area is defined by the top cell abutment box.

When placing a complete hierarchy, the abutment boxes of the cells (models) other than the top cell are sets identical to the one of the top cell and their instances are all placed at position (0,0,ID). That is, all the abutments boxes, whatever the hierarchical level, defines the same area (they are exactly superposed).

We choose this scheme because the placer will see all the instances as virtually flattened, so they can be placed anywhere inside the top-cell abutment box.

Computing the Placement Area

The placement area is computed using the etesian.aspectRatio and etesian.spaceMargin parameters only if the top-cell has an empty abutment box. If the top-cell abutment box has to be set, then it is propagated to all the instances models recursively.

Reseting the Placement

Once a placement has been done, the placer cannot reset it (will be implemented later). To perform a new placement, you must restart cgt. In addition, if you have saved the placement on disk, you must erase any .ap file, which are automatically reloaded along with the netlist (.vst).

Limitations

Etesian supports standard cells and fixed macros. As for the Coriolis 2.1 version, it doesn’t support movable macros, and you must place every macro beforehand. Timing and routability analysis are not included either, and the returned placement may be unroutable.

Etesian Configuration Parameters¶

Parameter Identifier	Type	Default
Etesian Parameters
`etesian.aspectRatio`	TypePercentage	100
`etesian.aspectRatio`	Define the height on width `H/W` aspect ratio, can be comprised between 10 and 1000
`etesian.spaceMargin`	TypePercentage	5
`etesian.spaceMargin`	The extra white space added to the total area of the standard cells
`etesian.uniformDensity`	TypeBool	False
`etesian.uniformDensity`	Whether the cells will be spread envenly across the area or allowed to form denser clusters
`etesian.effort`	TypeInt	2
`etesian.effort`	Sets the balance between the speed of the placer and the solution quality
`etesian.routingDriven`	TypeBool	False
`etesian.routingDriven`	Whether the tool will try routing iterations and whitespace allocation to improve routability; to be implemented
`etesian.graphics`	TypeInt	2
`etesian.graphics`	How often the display will be refreshed More refreshing slows the placer. `1` shows both upper and lower bounds `2` only shows lower bound results `3` only shows the final results

Knik – Global Router¶

The quality of Knik global routing solutions are equivalent to those of FGR 1.0. For an in-depth description of Knik algorithms, you may download the thesis of D. Dupuis avalaible from here~: Knik Thesis.

The global router is (not yet) deterministic. To circumvent this limitation, a global routing solution can be saved to disk and reloaded for later uses.

A global routing is saved into a file with the same name as the design and a kgr extention. It is in Box Router output format.

Menus:

$\textbf{P\&R} \rightarrow \textbf{Step by Step} \rightarrow \textbf{Save Global Routing}$
$\textbf{P\&R} \rightarrow \textbf{Step by Step} \rightarrow \textbf{Load Global Routing}$

Kite – Detailed Router¶

Kite no longer suffers from the limitations of Nero. It can route big designs as its runtime and memory footprint is almost linear (with respect to the number of gates). It has successfully routed design of more than 150K gates.

However, this first release comes with the temporary the following restrictions:

Works only with SxLib standard cell gauge.
Works always with 4 routing metal layers (M2 through M5).
Do not allow (take into account) pre-routed wires on signals other than power or ground.

Note

Slow Layer Assignment. Most of the time, the layer assignment stage is fast (less than a dozen seconds), but in some instances it can take more than a dozen minutes. This is a known bug and will be corrected in later releases.

After each run, Kite displays a set of completion ratios which must all be equal to 100% if the detailed routing has been successfull. In the event of a failure, on a saturated design, you may decrease the edge saturation ratio (argument –edge) to balance more evenly the design saturation. That is, the maximum saturation decrease at the price of a wider saturated area and increased wirelength. This is the saturation of the global router Knik, and you may increase/decrease by steps of 5%, which represent one track. The maximum capacity of the SxLib gauge is 10 tracks in two layers, that makes 20 tracks by Knik edge.

Routing a design is done in four ordered steps:

Detailed pre-route $\textbf{P\&R} \rightarrow \textbf{Step by Step} \rightarrow \textbf{Detailed PreRoute}$
Global routing $\textbf{P\&R} \rightarrow \textbf{Step by Step} \rightarrow \textbf{Global Route}$
Detailed routing $\textbf{P\&R} \rightarrow \textbf{Step by Step} \rightarrow \textbf{Detailed Route}$
Finalize routing $\textbf{P\&R} \rightarrow \textbf{Step by Step} \rightarrow \textbf{Finalize Route}$

It is possible to supply to the router a complete wiring for some nets that the user’s wants to be routed according to a specific topology. The supplied topology must respect the building rules of the Katabatic database (contacts must be, terminals, turns, h-tee & v-tee only). During the first step Detailed Pre-Route the router will solve overlaps between the segments, without making any dogleg. If no pre-routed topologies are present, this step may be ommited. Any net routed at this step is then fixed and become unmovable for the later stages.

After the detailed routing step the Kite data-structure is still active (the Hurricane wiring is decorated). The finalize step performs the removal of the Kite data-structure, and it is not advisable to save the design before that step.

You may visualize the density (saturation) of either Knik (on edges) or Kite (on GCells) until the routing is finalized. Special layers appears to that effect in the The Layers&Go Tab.

Kite Configuration Parameters¶

As Knik is only called through Kite, it’s parameters also have the kite. prefix.

The Katabatic parameters control the layer assignment step.

All the defaults value given below are from the default Alliance technology (cmos and SxLib cell gauge/routing gauge).

Parameter Identifier	Type	Default
Katabatic Parameters
`katabatic.topRoutingLayer`	TypeString	METAL5
`katabatic.topRoutingLayer`	Define the highest metal layer that will be used for routing (inclusive).
`katabatic.globalLengthThreshold`	TypeInt	1450
`katabatic.globalLengthThreshold`	This parameter is used by a layer assignment method which is no longer used (did not give good results)
`katabatic.saturateRatio`	TypePercentage	80
`katabatic.saturateRatio`	If `M(x)` density is above this ratio, move up feedthru global segments up from depth `x` to `x+2`
`katabatic.saturateRp`	TypeInt	8
`katabatic.saturateRp`	If a GCell contains more terminals (RoutingPad) than that number, force a move up of the connecting segments to those in excess
Knik Parameters
`kite.hTracksReservedLocal`	TypeInt	3
`kite.hTracksReservedLocal`	To take account the tracks needed inside a GCell to build the local routing, decrease the capacity of the edges of the global router. Horizontal and vertical locally reserved capacity can be distinguished for more accuracy.
`kite.vTracksReservedLocal`	TypeInt	3
`kite.vTracksReservedLocal`	cf. `kite.hTracksReservedLocal`
Kite Parameters
`kite.eventsLimit`	TypeInt	4000002
`kite.eventsLimit`	The maximum number of segment displacements, this is a last ditch safety against infinite loop. It’s perhaps a little too low for big designs
`kite.ripupCost`	TypeInt	3
`kite.ripupCost`	Differential introduced between two ripup cost to avoid a loop between two ripped up segments
`kite.strapRipupLimit`	TypeInt	16
`kite.strapRipupLimit`	Maximum number of ripup for strap segments
`kite.localRipupLimit`	TypeInt	9
`kite.localRipupLimit`	Maximum number of ripup for local segments
`kite.globalRipupLimit`	TypeInt	5
`kite.globalRipupLimit`	Maximum number of ripup for global segments, when this limit is reached, triggers topologic modification
`kite.longGlobalRipupLimit`	TypeInt	5
`kite.longGlobalRipupLimit`	Maximum number of ripup for long global segments, when this limit is reached, triggers topological modification

Executing Python Scripts in Cgt¶

Python/Stratus scripts can be executed either in text or graphical mode.

Note

How Cgt Locates Python Scripts: cgt uses the Python import mechanism to load Python scripts. So you must give the name of your script whitout .py extention and it must be reachable through the PYTHONPATH. You may uses the dotted module notation.

A Python/Stratus script must contains a function called ScriptMain() with one optional argument, the graphical editor into which it may be running (will be set to None in text mode). The Python interface to the editor (type: CellViewer) is limited to basic capabilities only.

Any script given on the command line will be run immediatly after the initializations and before any other argument is processed.

For more explanation on Python scripts see Python Interface for Hurricane / Coriolis.

Printing & Snapshots¶

Printing or saving into a pdf is fairly simple, just uses the File -> Print menu or the CTRL+P shortcut to open the dialog box.

The print functionality uses exactly the same rendering mechanism as for the screen, beeing almost WYSIWYG. Thus, to obtain the best results it is advisable to select the Coriolis.Printer look (in the Controller), which uses a white background and much suited for high resolutions 32x32 pixels patterns

There is also two mode of printing selectable through the Controller Settings -> Misc -> Printer/Snapshot Mode:

Mode	DPI (approx.)	Intended Usage
Cell Mode	150	For single `Cell` printing or very small designs. Patterns will be bigger and more readable.
Design Mode	300	For designs (mostly commposed of wires and cells outlines).

Note

The pdf file size Be aware that the generated pdf files are indeed only pixmaps. So they can grew very large if you select paper format above A2 or similar.

Saving into an image is subject to the same remarks as for pdf.

Memento of Shortcuts in Graphic Mode¶

The main application binary is cgt.

Category	Keys	Action
Moves	Up, Down Left, Right	Shift the view in the according direction
Fit	f	Fit to the Cell abutment box
Refresh	CTRL+L	Triggers a complete display redraw
Goto	g	apperture is the minimum side of the area displayed around the point to go to. It’s an alternative way of setting the zoom level
Zoom	z, m	Respectively zoom by a 2 factor and unzoom by a 2 factor
Zoom	Area Zoom	You can perform a zoom to an area. Define the zoom area by holding down the left mouse button while moving the mouse.
Selection	Area Selection	You can select displayed objects under an area. Define the selection area by holding down the right mouse button while moving the mouse.
	Toggle Selection	You can toggle the selection of one object under the mouse position by pressing CTRL and pressing down the right mouse button. A popup list of what’s under the position shows up into which you can toggle the selection state of one item.
	S	Toggle the selection visibility
Controller	CTRL+I	Show/hide the controller window. It’s the Swiss Army Knife of the viewer. From it, you can fine-control the display and inspect almost everything in your design.
Rulers	k, ESC	One stroke on k enters the ruler mode, in which you can draw one ruler. You can exit the ruler mode by pressing ESC. Once in ruler mode, the first click on the left mouse button sets the ruler’s starting point and the second click the ruler’s end point. The second click exits automatically the ruler mode.
Rulers	K	Clears all the drawn rulers
Print	CTRL+P	Currently rather crude. It’s a direct copy of what’s displayed in pixels. So the resulting picture will be a little blurred due to anti-aliasing mechanism.
Open/Close	CTRL+O	Opens a new design. The design name must be given without path or extention.
	CTRL+W	Close the current viewer window, but do not quit the application.
	CTRL+Q	CTRL+Q quit the application (closing all windows).
Hierarchy	CTRL+Down	Go one hierarchy level down. That is, if there is an instance under the cursor position, load it’s model Cell in place of the current one.
Hierarchy	CTRL+Up	Go one hierarchy level up. if we have entered the current model through CTRL+Down reload the previous model (the one in which this model is instanciated).

Cgt Command Line Options¶

Appart from the obvious --text options, all can be used for text and graphical mode.

Arguments	Meaning
-t\|–text	Instruct cgt to run in text mode.
-L\|–log-mode	Disable the uses of ansi escape sequence on the tty. Useful when the output is redirected to a file.
-c <cell>\|–cell=<cell>	The name of the design to load, without leading path or extention.
-g\|–load-global	Reload a global routing solution from disk. The file containing the solution must be named <cell>.kgr.
–save-global	Save the global routing solution, into a file named <design>.kgr.
-e <ratio>\|–edge=<ratio>	Change the edge capacity for the global router, between 0 and 1 (Knik).
-G\|–global-route	Run the global router (Knik).
-R\|–detailed-route	Run the detailed router (Kite).
-s\|–save-design=<routed>	The design into which the routed layout will be saved. It is strongly recommanded to choose a different name from the source (unrouted) design.
–events-limit=<count>	The maximal number of events after which the router will stops. This is mainly a failsafe against looping. The limit is sets to 4 millions of iteration which should suffice to any design of 100K. gates. For bigger designs you may wants to increase this limit.
–stratus-script=<module>	Run the Python/Stratus script `module`. See Python Scripts in Cgt.

Some Examples :

Run both global and detailed router, then save the routed design :

> cgt -v -t -G -R --cell=design --save-design=design_kite

Load a previous global solution, run the detailed router, then save the routed design :
```
> cgt -v -t --load-global -R --cell=design --save-design=design_kite
```
Run the global router, then save the global routing solution :
```
> cgt -v -t -G --save-global --cell=design
```

Miscellaneous Settings¶

Parameter Identifier	Type	Default
Verbosity/Log Parameters
`misc.info`	TypeBool	False
`misc.info`	Enable display of info level message (cinfo stream)
`misc.bug`	TypeBool	False
`misc.bug`	Enable display of bug level message (cbug stream), messages can be a little scarry
`misc.logMode`	TypeBool	False
`misc.logMode`	If enabled, assume that the output device is not a `tty` and suppress any escaped sequences
`misc.verboseLevel1`	TypeBool	True
`misc.verboseLevel1`	First level of verbosity, disable level 2
`misc.verboseLevel2`	TypeBool	False
`misc.verboseLevel2`	Second level of verbosity
Development/Debug Parameters
`misc.minTraceLevel`	TypeInt	0
`misc.maxTraceLevel`	TypeInt	0
`misc.maxTraceLevel`	Display trace information between those two levels (cdebug stream)
`misc.catchCore`	TypeBool	False
`misc.catchCore`	By default, cgt do not dump core. To generate one set this flag to True

The Controller¶

The Controller window is composed of seven tabs:

The Look Tab to select the display style.
The Filter Tab the hierarchical levels to be displayed, the look of rubbers and the dimension units.
The Layers&Go Tab to selectively hide/display layers.
The Netlist Tab to browse through the netlist. Works in association with the Selection tab.
The Selection Tab allow to view all the currently selected elements.
The Inspector Tab browse through either the DataBase, the Cell or the current selection.
The Settings Tab access all the tool’s configuration settings.

The Look Tab¶

You can select how the layout will be displayed. There is a special one Printer.Coriolis specifically designed for Printing & Snapshots. You should select it prior to calling the print or snapshot dialog boxes.

The Filter Tab¶

The filter tab let you select what hierarchical levels of your design will be displayed. Hierarchy level are numbered top-down: the level 0 correspond to the top-level cell, the level one to the instances of the top-level Cell and so on.

There are also check boxes to enable/disable the processing of Terminal Cell, Master Cells and Compnents. The processing of Terminal Cell (hierarchy leaf cells) is disabled by default when you load a hierarchical design and enabled when you load a single Cell.

You can choose what kind of form to give to the rubbers and the type of unit used to display coordinates.

Note

What are Rubbers: Hurricane uses Rubbers to materialize physical gaps in net topology. That is, if some wires are missing to connect two or more parts of net, a rubber will be drawn between them to signal the gap.

For example, after the detailed routing no rubbers should remains. They have been made very visibles as big violet lines...

The Layers&Go Tab¶

Control the individual display of all layers and Gos.

Layers correspond to a true physical layer. From a Hurricane point of view they are all the BasicLayers (could be matched to GDSII).
Gos stands from Graphical Objects, they are drawings that have no physical existence but are added by the various tools to display extra information. One good exemple is the density map of the detailed router, to easily locate congested areas.

For each layer/Go there are two check boxes:

The normal one triggers the display.
The red-outlined allows objects of that layer to be selectable or not.

The Netlist Tab¶

The Netlist tab shows the list of nets... By default the tab is not synched with the displayed Cell. To see the nets you must check the Sync Netlist checkbox. You can narrow the set of displayed nets by using the filter pattern (supports regular expressions).

An very useful feature is to enable the Sync Selection, which will automatically select all the components of the selected net(s). You can select multiple nets. In the figure the net auxsc35 is selected and is highlited in the Viewer.

The Selection Tab¶

The Selection tab list all the components currently selecteds. They can be filtered thanks to the filter pattern.

Used in conjunction with the Netlist Sync Selection you will all see all the components part of net.

In this list, you can toggle individually the selection of component by pressing the t key. When unselected in this way a component is not removed from the the selection list but instead displayed in red italic. To see where a component is you may make it blink by repeatedly press the t key...

The Inspector Tab¶

This tab is very useful, but mostly for Coriolis developpers. It allows to browse through the live DataBase. The Inspector provide three entry points:

DataBase: Starts from the whole Hurricane DataBase.
Cell: Inspect the currently loaded Cell.
Selection: Inspect the object currently highlited in the Selection tab.

Once an entry point has been activated, you may recursively expore all it’s fields using the right/left arrows.

Note

Do not put your fingers in the socket: when inspecting anything, do not modify the DataBase. If any object under inspection is deleted, you will crash the application...

Note

Implementation Detail: the inspector support is done with Slot, Record and getString().

The Settings Tab¶

Here comes the description of the Settings tab.