cadence simulation dumps

sharp@cadence.com wrote:

It certainly sounds reasonable that generating a smaller
binary file format should be faster than generating VCD.
I have heard that argument made before, and it always
sounds reasonable. However, I know that in the past,
actual measurements have shown that it is faster to dump
VCD than some binary formats. I don't know what the
reasons were, and perhaps things have changed.

It depends on how computationally expensive it is to write out the
binary file. If there's little more to the file format than dumping
out values similar to VCD (a version of the old MTI .wav file format
comes to mind), the binary will probably be faster. Once you throw in
stuff like clock/counter detection, signal value reordering and
indexing, etc in order to increase the compression ratio, you'll take a
speed hit. Likewise goes with any compression layers (e.g., libz) on
top of the data: you don't achieve a 50-100:1 compression ratio on VCD
without doing a bit of work.

There's also the factor that since VCD is built into the simulator/PLI
and isn't some standalone generic library code, it doesn't really need
to burn memory on storing signal names, their sizes, previous value,
etc so when it dumps there's less page/TLB thrashing on large models.
If it's faster to split a simrun that performs a binary dump into
simulating with writing VCD then converting it offline with a separate
utility, memory access issues are probably the case.

-t

 

Dear Jason,

You can use the Undertow waveform viewer to view data from the
ncverilog simulator. The $shm_open uses a format that is proprietary to
Cadence. With Undertow you can use a a PLI or VPI routine that is
included in the Undertow distribution. This will compress your output
by up to 1300 times over a VCD file, particularly when the VCD file
sizes are getting very large. Typical results with the Veritools'
PLI/VPI are as follows;

15 million gate/RTL gate equivalent design:

On a 650 MHZ Solaris system

VCD file, 39 minutes with file size of 3.1 gigabytes

PLI/VPLI output file 5.1 minutes, file size of 2.5 megabytes

On a 3.2 GHZ Linux System;

PLI/VPLI output file 1 minute, 40 seconds, file size 2.5 megabytes

The waveform file from the Veritools' PLI/VPI has been designed to load
in and display signals in Undertow almost instantly regardless of how
big this file is.
You can down load the software at no cost from www.veritools.com. Send
a request as directed to get username and passwd for downloading the
software and for getting a no cost license.

 

Hello
Does anyone can tell me how we can convert verilog code to VCD in Ncsim cadence.

Thanks