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If a SIMULA program has been developed which will be used very often,
e.g.   as  a  part in a regularly used production system, it is often
profitable to spend some efforts optimizing the program.

A central and sometimes non-trivial problem in  program  optimization
is  to  find  the  innermost loops of the program. Once the execution
profile of a program is known it is usually easy to  make  it  faster
with  a few changes such as modifications in processing algorithms or
by using a small machine language subroutine.

DEC-10 SIMULA is delivered with a frequency measurement system  which
assists  in  spotting  frequently executed parts of a SIMULA program.
The system consists of two SIMULA programs, FQCRED and FQCLST.

The system is used as follows:

The program to be analyzed must have been tested well enough  to  run
to  normal  completion.   It  is  read  by  the  program FQCRED which
produces two modified versions of it, one of which  is  a  compilable
SIMULA  program  (.FQ1+.FQ2)  and  the  other a listing later used to
produce  the  frequency  listing  (.FQD).   The  modified  compilable
program  is  executed  (.FQR) and produces, if normally terminated, a
file of measured frequencies (.FQS). This file  is  merged  with  the
listing  output from FQCRED by the program FQCLST, which produces the
final output (.FQL).

The user may also measure the execution time for different  parts  of
his  program by editing calls to a procedure Z_T(I) into his program.
A call with I > 0 initiates a timing which is ended by  a  call  with
the corresponding negative I. The logic is as follows:
+100>=I>0  T0[I]:= cptime;
-100<=I<0  J:=-I; ACC[J]:= ACC[J]+(cptime-T0[J]);
Calls to Z_T may be overlapping (even partly).

For example:

	....                |
	Z_T(+2);---------+  |
	....             |  |
	Z_T(+3);------+  |  |
	....          |  |  |
	Z_T(-2);------)--+  |
	....          |     |
	Z_T(-3);------+     |
	....                |

The resulting CPU-times will be presented at the end  of  the  result
file  (.FQL).  For  reliable results, do not try to measure too small
intervalls (depending on the precision of the timing). Note that only
such measurements that yielded accumulated times > 0 will be printed.

The measured program should satisfy some restrictions:

i)	The program must not contain the identifiers Z_Q, Z_T or Z__.

ii)	The  program  should not use any files on DSK: named
        <program name>.FQ1 .FQ2 .FQR .FQD .FQS .FQL or .FQT.

iii)	The program should terminate through its last END.
	I.e. not through call to Exit or through SIMDDT.

iv)	The source code lines should preferably not contain
	any internal TABs (leading TABs are OK). If so, the
	produced frequency indicators (|) might be misplaced
	(within such a line). TABs may be removed with
	.COPY temp.sim=prog.sim(W).

Note that the frequency indicators will be positioned  at  the  first
position  of  the  symbol  counted.  Its  related  number  should  be
interpreted as the number of times this symbol has been PASSED during
the  execution. An indicated label (L:) will thus tell how many times
control passed the label from left, excluding explicit jumps  (GO  TO

By  adding the switch /T to the filespecification requested by FQCRED
a trace file (.FQT) will be produced, containing the number  of  each
executed  (counted)  statement.  This  may  be  useful when debugging
Simulation programs or programs making use of resume/detach.  If  the
program  terminates  with  an  error the file with logical name TRACE
must be closed before leaving SIMDDT.

The result file (.FQL) will contain information about the  number  of
the  first traced statement on each source line. Consequetive numbers
will be indicated as xx-yy in .FQT. Note that the file is created  in
APPEND  mode adding new traces to the end of the file. The trace file
will contain the first six characters of the traced  symbol  followed
by its statement number.

Adding a number to the trace switch (/T:x) will  trace  the  executed
statements  the  first  x  times.  Every  statement  number  will  be
displayed (no xx-yy compacting). X must be >= 0, /T:0  is  equivalent
to /T.

The  use  of tracing will considerably increase the execution time of
the modified program. Thus it is not recommended to use timing  (Z_T)
together with tracing. The tracing may be switched off by calling the
procedure TRACEOFF. It may be activated again by calling TRACEON.

If you want to include any of your external modules in the  analysis,
run the program SIMEXP prior to FQCRED.

The following session illustrates the use of the system on the SIMULA
program FLOPY.SIM.

	.run pub:fqcred

	Welcome to FQCRED Version 3


	[FQCRED: CPU time: 0.88]
	Running modified program: SIMULA:  FLOPY
	LINK:	Loading
	[LNKXCT FLOPY Execution]

	If you want to have the result at once type .CONTINUE
	To accumulate the frequencies just type: START


	Welcome to FQCLST Version 3

	Result on file: DSK: FLOPY.FQL - Type CON to see them at once.


	 Max   --------------------- FQC Result ---------------------

	            INTEGER u,k;   TEXT t;
	     1      |1
	            WHILE Draw(0.999,u) DO u:= u+2;
	  1636      |1                     |1636
	     1      |1
	     1      |1
	            FOR u:= 1 STEP 1 UNTIL 5000 DO
	     1      |1
	            IF t = NOTEXT THEN k:=k+1;
	  5000      |5000              |5000
	     1      |1
	     1      |1
	            FOR u:= 1 STEP 1 UNTIL 5000 DO
	     1      |1
	            IF t == NOTEXT THEN k:=k+1;
	  5000      |5000               |5000
	     1      |1
	     1      |1
	            FOR u:= 1 STEP 1 UNTIL 5000 DO
	     1      |1
	            IF TRUE THEN k:=k+1;
	  5000      |5000        |5000
	     1      |1
	     1  |1

	FQC results:
	Max frequency:      5000
	Sum frequency:     31649
	No. of executions:     1

	CPU timing: Total   0.50 sec.

	Call no.    Time spent    % of runtime
	    1          0.047           9.46
	    2          0.248          49.90
	    3          0.095          19.11
	    4          0.089          17.91

	.DIRECT flopy

	FLOPY	SIM     1  <057>   8-Aug-78   User program
	FLOPY	FQ1     4  <057>   8-Aug-78   Modif. file part 1
	FLOPY	FQ2     3  <057>   8-Aug-78   Modif. file part 2
	FLOPY	FQD     1  <057>   8-Aug-78   Edited file with bars (|)
	FLOPY	FQR    11  <057>   8-Aug-78   REL-file from FQ1+FQ2
	FLOPY	FQS     1  <057>   8-Aug-78   Frequency + timing data (binary)
	FLOPY	FQL     3  <057>   8-Aug-78   Result file (FQS+FQD)

Cleaning up afterwards might be done with .DELETE *.FQ?

		[End of FQC.HLP 78-08-16 MO]