Re: Possible huge setarrvalue optimization

[Sebastian Gniazdowski <psprint@fastmail.com>]

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Hello,
I attach patch that needs one problem to be resolved. Gains for
following test code:

test_fun() {
    arr[20000]=""
    repeat 10000; do
        arr[10000]="x"
    done
}

are huge: 37969 ms with no optimization, 244 ms with optimization. The
screensaver runs for 495 sec without optimization, 51 sec with opt
(still slower than hash which runs for 23 sec).

I changed:

        if (v->end <= pre_assignment_length)
            post_assignment_length += pre_assignment_length - v->end +
            1;

to:

        if (v->end <= pre_assignment_length)
            post_assignment_length += pre_assignment_length - v->end;

And this allows to test post* == pre*. I think the "+ 1" isn't needed,
v->end can be treated as "number of elements affected already".
Subtracting the number of elements from pre_assignment_length gives
correct value: elements that will be copied from old.

The thing that has to be resolved: special setters. The patch contains
one special handler tested:

if ( pre_assignment_length != post_assignment_length ||
v->pm->gsu.a->setfn == set_region_active ) {

But this doesn't work as the symbol `set_region_active` isn't available.
How to solve this, and what are other special handlers? One test is
failing (A06) – append to typeset -U array, because the special setter
isn't called.

-- 
  Sebastian Gniazdowski
  psprint@fastmail.com

[-- Attachment #2: array_big_opt.diff --]
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diff --git a/Src/params.c b/Src/params.c
index ef72cba..e23a0af 100644
--- a/Src/params.c
+++ b/Src/params.c
@@ -2654,24 +2654,34 @@ setarrvalue(Value v, char **val)
 	    v->end = v->start;
 
 	post_assignment_length = v->start + arrlen(val);
-	if (v->end <= pre_assignment_length)
-	    post_assignment_length += pre_assignment_length - v->end + 1;
-
-	p = new = (char **) zshcalloc(sizeof(char *)
-		                      * (post_assignment_length + 1));
-
-	for (i = 0; i < v->start; i++)
-	    *p++ = i < pre_assignment_length ? ztrdup(*q++) : ztrdup("");
-	for (r = val; *r;) {
-            /* Give away ownership of the string */
-	    *p++ = *r++;
-	}
-	if (v->end < pre_assignment_length)
-	    for (q = old + v->end; *q;)
-		*p++ = ztrdup(*q++);
-	*p = NULL;
 
-	v->pm->gsu.a->setfn(v->pm, new);
+	if (v->end <= pre_assignment_length)
+	    post_assignment_length += pre_assignment_length - v->end;
+
+        if ( pre_assignment_length != post_assignment_length || v->pm->gsu.a->setfn == set_region_active ) {
+            p = new = (char **) zshcalloc(sizeof(char *)
+                                          * (post_assignment_length + 1));
+
+            for (i = 0; i < v->start; i++)
+                *p++ = i < pre_assignment_length ? ztrdup(*q++) : ztrdup("");
+            for (r = val; *r;) {
+                /* Give away ownership of the string */
+                *p++ = *r++;
+            }
+            if (v->end < pre_assignment_length)
+                for (q = old + v->end; *q;)
+                    *p++ = ztrdup(*q++);
+            *p = NULL;
+
+            v->pm->gsu.a->setfn(v->pm, new);
+        } else {
+            /* v->start is 0-based */
+            p = old + v->start;
+            for (r = val; *r;) {
+                /* Give away ownership of the string */
+                *p++ = *r++;
+            }
+        }
 
         /* Ownership of all strings has been
          * given away, can plainly free */

[-- Attachment #3: testopt7.zsh --]
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#!/usr/local/bin/zsh-arr-assign
#!/usr/local/bin/zsh-arr-assign-before

zmodload zsh/zprof

typeset -a arr

test_fun() {
    arr[20000]=""
    repeat 10000; do
        arr[10000]="x"
    done
}

test_fun

print -rl $arr[@] $arr[10000]

zprof