CGT - The Graphical Interface

The Coriolis graphical interface is split up into two windows.

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

Features are detailed in Viewer & Tools.

• The Controller, which allows to:
  • Tweak what is displayed 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 gives 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: a same logical instance cannot have two different placements. So, if you don’t supply a placement for it, it will be uniquified (cloned) and you will see the copy files appears on disk upon saving.

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 set 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, define 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	Percentage	100
	Define the height on width H/W aspect ratio, can be comprised between 10 and 1000
etesian.spaceMargin	Percentage	5
	The extra white space added to the total area of the standard cells
etesian.uniformDensity	Bool	False
	Whether the cells will be spread envenly across the area or allowed to form denser clusters
etesian.effort	Int	2
	Sets the balance between the speed of the placer and the solution quality
etesian.routingDriven	Bool	False
	Whether the tool will try routing iterations and whitespace allocation to improve routability; to be implemented
etesian.graphics	Int	2
	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

Katana – Global Router

The quality of Katana global routing solutions are equivalent to those of FGR 1.0. For an in-depth description of Katana algorithms, you may download the thesis of D. Dupuis avalaible from here~: Knik Thesis (Knik has been rewritten as part of Katana, the algorithms remains essentially the same).

The global router is now deterministic.

Katana – Detailed Router

Katana 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.

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, Katana displays a set of completion ratios which must all be equal to 100% or (NNNN+0) if the detailed routing has been successfull. In the event of a failure, on a saturated design, you may tweak the three following configuration parameters:

1. katana.hTrackReservedLocal, the number of track reserved for local routing, that quantity is substracted from the edge capacities (global routing) to give a sense of the cluttering inside the GCells.
2. katana.vTrackReservedLocal, same as above.
3. etesian.spaceMargin, increases the free area of the overall design so the routing density decrease.

The idea is to increase the horizontal and vertical local track reservation until the detailed router succeeds. But in doing so we make the task of the global router more and more difficult as the capacity of the edges decreases, and at some point it will fail too. So this is a balance.

Routing a design is done in four ordered steps:

1. Detailed pre-route
2. Global routing
3. Detailed routing
4. Finalize routing

It is possible to supply to the router a complete wiring for some nets that the user wants to be routed according to a specific topology. The supplied topology must respect the building rules of the Anabatic 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 Katana data-structure is still active (the Hurricane wiring is decorated). The finalize step performs the removal of the Katana data-structure, and it is not advisable to save the design before that step.

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

Katana Configuration Parameters

The Anabatic 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
Anabatic Parameters
anabatic.topRoutingLayer	String	METAL5
	Define the highest metal layer that will be used for routing (inclusive).
anabatic.globalLengthThreshold	Int	1450
	This parameter is used by a layer assignment method which is no longer used (did not give good results)
anabatic.saturateRatio	Percentage	80
	If M(x) density is above this ratio, move up feedthru global segments up from depth x to x+2
anabatic.saturateRp	Int	8
	If a GCell contains more terminals (RoutingPad) than that number, force a move up of the connecting segments to those in excess
anabatic.globalIterations	Int	10
	The maximum number of iterations the global router will try to solve edges overload
Katana Parameters
katana.hTracksReservedLocal	Int	3
	To take account the tracks needed inside a GCell to build the local routing the capacities of the edges needs to be decreased. The decrease is computed by the GCell and cannot exceed this number (this is maximum). For better accuracy vertical and horizontal edges are distinguisheds
katana.vTracksReservedLocal	Int	3
	cf. kite.hTracksReservedLocal
katana.eventsLimit	Int	4000002
	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
katana.ripupCost	Int	3
	Differential introduced between two ripup costs to avoid a loop between two ripped up segments
katana.strapRipupLimit	Int	16
	Maximum number of ripup for strap segments
katana.localRipupLimit	Int	9
	Maximum number of ripup for local segments
katana.globalRipupLimit	Int	5
	Maximum number of ripup for global segments, when this limit is reached, triggers topologic modification
katana.longGlobalRipupLimit	Int	5
	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 whithout .py extension and it must be reachable through the PYTHONPATH. You may use the dotted module notation.

A Python/Stratus script must contain 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 to Coriolis.

Printing & Snapshots

Printing or saving into a pdf is fairly simple, just use 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 well suited for high resolutions 32x32 pixels patterns

There is also two modes 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	Shifts the view in the according direction
Fit	f	Fits 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
	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.
	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	Closes the current viewer window, but does not quit the application.
	CTRL+Q	CTRL+Q quits the application (closing all windows).
Hierarchy	CTRL+Down	Goes one hierarchy level down. That is, if there is an instance under the cursor position, loads its model Cell in place of the current one.
	CTRL+Up	Goes one hierarchy level up. If we have entered the current model through CTRL+Down reloads 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	Instructs cgt to run in text mode.
-L|–log-mode	Disables the use 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.
-m <val>|–margin=<val>	Percentage val of white space for the placer (Etesian).
–events-limit=<count>	The maximal number of events after which the router will stop. This is mainly a failsafe against looping. The limit is set to 4 millions of iteration which should suffice to any design of 100K. gates. For bigger designs you may want to increase this limit.
-G|–global-route	Runs the global router (Katana).
-R|–detailed-route	Runs the detailed router (Katana).
-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.
–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_r
  

Miscellaneous Settings

Parameter Identifier	Type	Default
Verbosity/Log Parameters
misc.info	Bool	False
	Enables display of info level message (cinfo stream)
misc.bug	Bool	False
	Enables display of bug level message (cbug stream), messages can be a little scarry
misc.logMode	Bool	False
	If enabled, assumes that the output device is not a tty and suppresses any escape sequences
misc.verboseLevel1	Bool	True
	First level of verbosity, disables level 2
misc.verboseLevel2	Bool	False
	Second level of verbosity
Development/Debug Parameters
misc.minTraceLevel	Int	0
misc.maxTraceLevel	Int	0
	Displays trace information between those two levels (cdebug stream)
misc.catchCore	Bool	False
	By default, cgt does not dump core. To generate one set this flag to True

The Controller

The Controller window is composed of seven tabs:

1. The Look Tab to select the display style.
2. The Filter Tab the hierarchical levels to be displayed, the look of rubbers and the dimension units.
3. The Layers&Go Tab to selectively hide/display layers.
4. The Netlist Tab to browse through the netlist. Works in association with the Selection tab.
5. The Selection Tab allows to view all the currently selected elements.
6. The Inspector Tab browses through either the DataBase, the Cell or the current selection.
7. The Settings Tab accesses 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 corresponds 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 Components. 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 rubber should remain. They have been made very visible as big violet lines...

The Layers&Go Tab

Control the individual display of all layers and Gos.

• Layers correspond to true physical layers. 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).

A 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 highlighted in the Viewer.

The Selection Tab

The Selection tab lists all the components currently selected. 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 provides three entry points:

• DataBase: Starts from the whole Hurricane DataBase.
• Cell: Inspects the currently loaded Cell.
• Selection: Inspects the object currently highlighted in the Selection tab.

Once an entry point has been activated, you may recursively expore all its 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.