Hi,

I would like to verify the performance of a behavioral model in transient by checking out how much time the simulation that I use it in needs for the implicit DC, as well as how many Newton iterations it performs during each transient step. Is there a way to get that information from Spectre? I tried to search the documentation that comes through spectre -h, but couldn't find any reference.

Marq

Hi Geoffrey,

Thanks - I had already considered that approach, but I had hoped there might be some built-in debug output from Spectre that could help me. The Verilog-A $debug approach will obviously have an effect on throughput time. I guess I will have to try the $debug approach.

Marq.

OK, for the benefit of the community here is the $debug Verilog-A code as well as a very kludgy shell script that does the extraction of the iteration data. It now returns the average number of iterations and the maximum number of iterations. With a little more work the variation (in terms of a Poisson distribution, of course) could be extracted as well.

This is the Verilog-A code of a simple module that writes the data out to the logfile in case of Spectre.

Code:

module stepcount;

  integer count;

  analog
    begin
	if (analysis("static")) begin
	  $debug("MINOR (DC)");
	  $strobe("MAJOR (DC) %d", count);
	end
	else
	if (analysis("tran") && !analysis("static")) begin
	  $debug("MINOR (TRAN)");
	  $strobe("MAJOR (TRAN) %d", count);
	end
	count = count + 1;
    end

endmodule // stepcount
 

And this is a function in Korn shell (/bin/ksh) style that extracts the data from the log file and creates a number of local variables that can be written out at a later stage. With some minor effort this can be turned into a more efficient Perl or Python script that does all of it and more.

Code:

IterationCount() {		# count the number of major and minor steps in
				# the logfile $2 and number of accepted steps $3
					  # if the flag $1 is 1.
  if [[ $1 -gt 0 ]]
  then \
    (( hasstepcount=1-$(grep -q -e '^MAJOR ' $2 ; echo $?) ))
    if [[ ${hasstepcount} -gt 0 ]]
    then \
	(( nminordc=$(grep -c -e '^MINOR (DC)' $2) ))
	(( nmajordc=$(grep -c -e '^MAJOR (DC)' $2) ))

	(( nminortr=$(grep -c -e '^MINOR (TRAN)' $2) ))
	(( nmajortr=$(grep -c -e '^MAJOR (TRAN)' $2) ))
	(( aveminortr=${nminortr}*1.0/${nmajortr} ))
	(( maxminortr=0 ))
	linetext0=$(grep -n -m 1 -e '^MINOR (TRAN)' $2)
	(( linenr0=$(python -c 'import sys ; s=sys.argv[1] ; r1=s.split(":")[0] ; print r1,' ${linetext0})-1 ))
	for (( count=1 ; $3-${count} ; count=${count}+1 ))
	do \
	  findtext="^MAJOR (TRAN) ${count}"
	  linetext1=$(grep -n -m 1 -e "${findtext}" $2)
	  (( linenr1=$(python -c 'import sys ; s=sys.argv[1] ; r1=s.split(":")[0] ; print r1,' ${linetext1}) ))
	  (( nlines=${linenr1}-${linenr0}-1 ))
	  if [[ ${maxminortr} -lt ${nlines} ]]
	  then \
	    (( maxminortr=${nlines} ))
	  fi
	  (( linenr0=${linenr1} ))
	done
    else \
	IterationCount 0 $2 $3
    fi
  else \
    (( nminordc=0 ))
    (( nmajordc=1 ))
    (( nminortr=0 ))
    (( nmajortr=$3 ))
    (( aveminortr=0.0 ))
    (( maxminortr=0 ))
  fi
}