Compare computation time between aux and let

compare-aux-let.l

(defun test1
    (&aux a b c)
  a
  )

(defun test2
    ()
  (let (a b c)
    a
    ))

(defun test3
    ()
  (let* (a b c)
    a
    ))

(print "use aux")
(bench (dotimes (i 5000000) (test1)))
(print "use let")
(bench (dotimes (i 5000000) (test2)))
(print "use let*")
(bench (dotimes (i 5000000) (test3)))

example-result.txt

$ roseus hoge.l 
configuring by "/opt/ros/melodic/share/euslisp/jskeus/eus//lib/eusrt.l"
;; readmacro ;; object ;; packsym ;; common ;; constants ;; stream ;; string ;; loader ;; pprint ;; process ;; hashtab ;; array ;; mathtran ;; eusdebug ;; eusforeign ;; coordinates ;; tty ;; history ;; toplevel ;; trans ;; comp ;; builtins ;; par ;; intersection ;; geoclasses ;; geopack ;; geobody ;; primt ;; compose ;; polygon ;; viewing ;; viewport ;; viewsurface ;; hid ;; shadow ;; bodyrel ;; dda ;; helpsub ;; eushelp ;; xforeign ;; Xdecl ;; Xgraphics ;; Xcolor ;; Xeus ;; Xevent ;; Xpanel ;; Xitem ;; Xtext ;; Xmenu ;; Xscroll ;; Xcanvas ;; Xtop ;; Xapplwin 
connected to Xserver DISPLAY=:0
X events are being asynchronously monitored.
;; pixword ;; RGBHLS ;; convolve ;; piximage ;; pbmfile ;; image_correlation ;; oglforeign ;; gldecl ;; glconst ;; glforeign ;; gluconst ;; gluforeign ;; glxconst ;; glxforeign ;; eglforeign ;; eglfunc ;; glutil ;; gltexture ;; glprim ;; gleus ;; glview ;; toiv-undefined ;; fstringdouble irtmath irtutil irtc irtgeoc irtgraph ___time ___pgsql irtgeo euspqp pqp irtscene irtmodel irtdyna irtrobot irtsensor irtbvh irtcollada irtpointcloud irtx eusjpeg euspng png irtimage irtglrgb 
;; extending gcstack 0x55ff1ed1b690[16374] --> 0x55ff1f1a0b70[32748] top=3d61
irtgl irtglc irtviewer 
EusLisp 9.26( 1.2.1) for Linux64 created on ip-172-30-1-203(Fri May 31 16:58:14 PST 2019)
roseus ;; loading roseus("1.7.4") on euslisp((9.26 ip-172-30-1-203 Fri May 31 16:58:14 PST 2019  1.2.1))
eustf roseus_c_util
"use aux"
;; time -> 0.738809[s]
"use let"
;; time -> 0.889221[s]
"use let*"
;; time -> 0.842709[s]

I performed some tests in my environment and got the same results. &aux faster than let* faster than let. Actually was also surprised that sequential let is faster than the parallel one.

The &aux bind is:

    while (iscons(formal)) {
      fvar=ccar(formal); formal=ccdr(formal);
      if (iscons(fvar)) {
        initform=ccdr(fvar);
        fvar=ccar(fvar);
        if (iscons(initform)) {GC_POINT;aval=eval(ctx,ccar(initform));}
        else aval=NIL;}
      else aval=NIL;
      env=vbind(ctx,fvar,aval,env,bf); }

and the let* bind is:

  while (islist(vlist)) {
    GC_POINT;
    var=ccar(vlist); vlist=ccdr(vlist);
    if (islist(var)) {
      init=ccdr(var); var=ccar(var);
      if (islist(init)) init=eval(ctx,ccar(init));
      else init=NIL;}
    else init=NIL;
    env=vbind(ctx,var,init,env,bf);
    }

Not much difference in here, so the time delay is probably due to the calling of the eus function.

Overall I would say that &aux is good for optimization, and let for readability.
Thanks for the discussion.

What does sequential let is faster than the sequential one mean?

Sorry, fixed that typo on the above comment.