Hi Folks,
(below)
Quoting Ben Coman <[email protected]>:
On Sat, May 9, 2015 at 10:35 PM, Eliot Miranda <[email protected]>
wrote:
On Sat, May 9, 2015 at 7:09 AM, Ben Coman <[email protected]> wrote:
From my limited experience bug hunting, calling #changed: from a thread
other than the UI thread is a source of evil. There are too many
assumptions throughout the system that the UI is single threaded. Can
anyone advise me that is not a proper belief?
Then that implies that a Transcript implementation where #nextPut: direct
calls #changed:
is not appropriate for use with multi-threaded applications. In Pharo,
#changed: is only called from #stepGlobal, which is called from
doOneCycle:. (This came about as a last minute bug fix before Pharo 3
release and maybe could use some cleanup.
Separating the UI from Transcript into its own viewer might be a good
idea, but actually it would not solve Stef's case since his code would
still be running in the UI thread -- unless the viewer ran in another
thread, which would have its own complexities.
I think the point about efficiency is significant. The following
example...
Time millisecondsToRun: [ 1000 timesRepeat: [ Transcript show: 'x'
] ]
on Squeak 4.5 --> 12749ms
on Pharo 50029 --> 2ms
This better performance helped me a lot trying to understand the high
priority timerEventLoop being able to indiscriminately scatter Transcript
tracing through that code. I believe its also probably beneficial for
working with externally triggered semaphores and timing sensitive race
conditions.
So we have two mutually exclusive cases:
* better interactivity, poorer system performance
* faster system performance, worse interactivity
Which of these is broken depends on your viewpoint.
Something that runs fast but is incorrect is still incorrect. The fact
that the transcript doesn't output until a world step is possible is a
bug. It forces programs that use the transcript to be rewritten in order
to see transcript output.
As a point of comparison for correctness, for the following...
Transcript clear.
[ $a asciiValue to: $z asciiValue do: [ :c |
[ 1 to: 9 do: [ :i | Transcript show: c asCharacter printString , i
printString , ' ' ] ] forkAt: 40
].
] forkAt: 41
Squeak 4.5 gives...
$a1 $a2 $a3 $a4 $a5 $a6 $a7 $a8 $a9 $b1 $b2 $b3 $b4 $b5 $b5 $c1 $c2 $c3 $c4
$c5 $c6 $c7 $c8 $c9 $d1 $d2 $d3 $d4 $d5 $d6 $d7 $d8 $d9 $d9 $e2 $g2 $h2 $h2
$i2 $k2 $k2 $l2 $n2 $n2 $o2 $o2 $r2 $s2 $t2 $u2 $u2 $v2 $x2 $y2 $z2 $z2 $b7
$f3 $e3 $e3 $g3 $j3 $h3 $i3 $k3 $k3 $m3 $n3 $p3 $p3 $q3 $o3 $s3 $t3 $t3 $u3
$v3 $x3 $y3 $z3 $b8 $f4 $e4 $e4 $g4 $h4 $i4 $k4 $l4 $m4 $m4 $n4 $r4 $q4 $o4
$o4 $s4 $w4 $u4 $u4 $v4 $y4 $y4 $z4 $z4 $f5 $j5 $j5 $g5 $i5 $k5 $l5 $l5 $m5
$m5 $n5 $q5 $o5 $s5 $s5 $t5 $u5 $u5 $x5 $y5 $z5 $f6 $f6 $h6 $h6 $g6 $g6 $k6
$p6 $m6 $r6 $r6 $n6 $o6 $s6 $s6 $w6 $u6 $x6 $x6 $e7 $f7 $j7 $h7 $h7 $i7 $l7
$l7 $k7 $m7 $m7 $q7 $n7 $n7 $o7 $t7 $w7 $w7 $u7 $v7 $x7 $z7 $z7 $e8 $e8 $h8
$g8 $i8 $i8 $l8 $k8 $k8 $m8 $q8 $n8 $n8 $s8 $t8 $w8 $y8 $y8 $u8 $x8 $z8 $f9
$f9 $e9 $h9 $h9 $g9 $p9 $p9 $k9 $r9 $r9 $m9 $n9 $n9 $o9 $t9 $t9 $w9 $v9 $u9
$u9 $z9 $x9
Pharo 50041 gives...
$a1 $a2 $a3 $a4 $a5 $a6 $a7 $a8 $a9 $b1 $b2 $b3 $b4 $b5 $b6 $b7 $b8 $b9 $c1
$c2 $c3 $c4 $c5 $c6 $c7 $c8 $c9 $d1 $d2 $d3 $d4 $d5 $d6 $d7 $d8 $d9 $e1 $e2
$e3 $e4 $e5 $e6 $e7 $e8 $e9 $f1 $f2 $f3 $f4 $f5 $f6 $f7 $f8 $f9 $g1 $g2 $g3
$g4 $g5 $g6 $g7 $g8 $g9 $h1 $h2 $h3 $h4 $h5 $h6 $h7 $h8 $h9 $i1 $i2 $i3 $i4
$i5 $i6 $i7 $i8 $i9 $j1 $j2 $j3 $j4 $j5 $j6 $j7 $j8 $j9 $k1 $k2 $k3 $k4 $k5
$k6 $k7 $k8 $k9 $l1 $l2 $l3 $l4 $l5 $l6 $l7 $l8 $l9 $m1 $m2 $m3 $m4 $m5 $m6
$m7 $m8 $m9 $n1 $n2 $n3 $n4 $n5 $n6 $n7 $n8 $n9 $o1 $o2 $o3 $o4 $o5 $o6 $o7
$o8 $o9 $p1 $p2 $p3 $p4 $p5 $p6 $p7 $p8 $p9 $q1 $q2 $q3 $q4 $q5 $q6 $q7 $q8
$q9 $r1 $r2 $r3 $r4 $r5 $r6 $r7 $r8 $r9 $s1 $s2 $s3 $s4 $s5 $s6 $s7 $s8 $s9
$t1 $t2 $t3 $t4 $t5 $t6 $t7 $t8 $t9 $u1 $u2 $u3 $u4 $u5 $u6 $u7 $u8 $u9 $v1
$v2 $v3 $v4 $v5 $v6 $v7 $v8 $v9 $w1 $w2 $w3 $w4 $w5 $w6 $w7 $w8 $w9 $x1 $x2
$x3 $x4 $x5 $x6 $x7 $x8 $x9 $y1 $y2 $y3 $y4 $y5 $y6 $y7 $y8 $y9 $z1 $z2 $z3
$z4 $z5 $z6 $z7 $z8 $z9
(start your comparison at $b5)
So in one axis Pharo has improved Transcript, but we didn't notice the
significance of the use case we lost.
cheers -ben
Please take a good look at Cuis' Transcript and consider using it.
By default, the display is updated immediately, but without calling
Morphic, it can even work with no UI framework at all. It does updates
faster than Squeak or Visualworks:
Time millisecondsToRun: [ 1000 timesRepeat: [ Transcript
show: 'x' ] ]. 763.
But if you want minimum overhead without immediate feedback:
Time millisecondsToRun: [ Transcript showOnDisplay: false.
1000 timesRepeat: [ Transcript show: 'x' ]. Transcript showOnDisplay:
true ]. 1.
"As fast as Pharo"
It is also thread safe, and for Ben's example:
Transcript clear.
[
$a asciiValue to: $z asciiValue do: [ :c |
[ 1 to: 9 do: [ :i | Transcript show: c asCharacter printString , i
printString , ' ' ] ] forkAt: 40
].
] forkAt: 41
it gives the same result as Pharo.
The fact that the updates are not bound to Morphic also means that it
is possible to do #show: deep in Morphic logic, without causing
infinite loops or recursions, and get immediate feedback. It has
proved to be a useful aid in debugging Morphic code.
Cheers,
Juan Vuletich
