The Open Cell Geometry Digest Panel

This panel is used to create a new Cell Geometry Digest in memory, which is added to the listing in the Cell Geometry Digests panel. This panel is brought up with the Add button in the Cell Hierarchy Digests panel.

There are three ``notebook'' tabs that correspond to the three types of CGD. Each corresponding page contains controls for setting the parameters appropriate for the selected CGD type.

in memory
The in memory tab corresponds to a ``memory'' CGD. This type of CGD saves all geometry data in memory. The geometry data are highly compressed, so that this makes sense even for very large layouts.

The source from which to create the CGD is entered into the entry area at the top of the page. The source can be one of the following:

1. A path to a layout (archive) file.
   
2. The access name of a CHD already in memory.
   
3. A path to a saved CHD file.
   
4. A path to a saved CGD file.
   

If the source is a layout file, one can apply layer filtering as the file is being read. It is also possible to apply cell name mapping. If mapping is employed, layer data are accessed via the modified cell names. If the CGD is to be linked with a CHD, the cell name mapping, if any is used, should be the same when creating the CHD and the CGD. The control groups below the entry expose the layer filtering and cell name mapping capabilities.

If the source is a CHD access name, or a CHD file, the cell name mapping is automatically set to the same as was used in creating the CHD. The layer filtering is available if the source is a CHD access name, or if the source is a CHD file saved without geometry records (with the Save button in the Cell Hierarchy Digests panel). If the source is a CHD file containing geometry records, the CGD uses those geometry records verbatim.

If the source is a saved CGD file (from the Save button in the Cell Geometry Digests panel), the CGD will import this file verbatim.

file reference
The file reference tab corresponds to a ``file'' CGD. This type of CGD stores offsets into a CGD file on disk. The disk file can potentially also contain a CHD representation. This access method is not quite as fast as the in-memory variant, but is still generally much faster that reading the original layout file since 1) the data are highly compressed so fewer bytes are read, and 2) the data are sorted by layer so per-layer searches are more direct.

This page consists of an entry area, into which a source is entered. The source can be either a path to a saved CGD file, or to a saved CHD file that contains geometry records. In either case, the new CGD is created to reference the geometry data by offset into the source file.

During its lifetime, this type of CGD maintains an open file descriptor to its source file. Although it is not likely, it may be possible to hit a system limit for open file descriptors if too many file CGDs are simultaneously open.

remote server reference
The remote server reference tab corresponds to a ``remote access'' CGD. This type of CGD obtains geometry data from a remote host which is running Xic in server mode (see 4.5). The remote access CGD is a stub which links to a CGD in server memory, and data are returned via interprocess communication calls.

This page provides separate entry areas for the host name, port, and remote CGD access name. These correspond to the remote host running the Xic server, which must have a CGD in memory (of any type). The new CGD will transparently link to the remote CGD, under a local access name.

The Host name entry must contain the network host name of the machine running the server. The Port number is optional, if not specified the port used defaults to 6115, which is the IANA registered port number for the ``xic/tcp'' service. If the server is for some reason using a different port number, that same port number must be entered. The access name of the CGD to reference on the server must be entered into the Server CGD access name entry area.

During its lifetime, this type of CGD maintains an open socket to the server. Since the number of connections is limited, it is best to free this type of CGD as soon as possible.

Below the notebook area is an entry for access name. This is the name under which the new CGD will be listed in the Cell Geometry Digests panel. A default is provided that is guaranteed not to conflict with an existing CGD.

The user can specify an access name. If the name is in use by an existing CGD, and the existing CGD is not linked to a CHD, it will be destroyed, and the new CGD will be created and saved under the same name. However, if the existing CGD is linked, it cannot be destroyed, and the CGD creation will fail with an error message.

When the Apply button is pressed, if all goes properly the source will be processed, the new CGD will be created, and added to the list in memory under the access name given.