From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 12327 invoked by alias); 18 Nov 2016 06:17:18 -0000 Mailing-List: contact zsh-workers-help@zsh.org; run by ezmlm Precedence: bulk X-No-Archive: yes List-Id: Zsh Workers List List-Post: List-Help: X-Seq: 39971 Received: (qmail 11019 invoked from network); 18 Nov 2016 06:17:18 -0000 X-Qmail-Scanner-Diagnostics: from new2-smtp.messagingengine.com by f.primenet.com.au (envelope-from , uid 7791) with qmail-scanner-2.11 (clamdscan: 0.99.2/21882. spamassassin: 3.4.1. Clear:RC:0(66.111.4.224):SA:0(-0.7/5.0):. Processed in 1.05922 secs); 18 Nov 2016 06:17:18 -0000 X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on f.primenet.com.au X-Spam-Level: X-Spam-Status: No, score=-0.7 required=5.0 tests=FREEMAIL_FROM, RCVD_IN_DNSWL_LOW,SPF_PASS,T_DKIM_INVALID autolearn=unavailable autolearn_force=no version=3.4.1 X-Envelope-From: psprint@fastmail.com X-Qmail-Scanner-Mime-Attachments: | X-Qmail-Scanner-Zip-Files: | Received-SPF: pass (ns1.primenet.com.au: SPF record at spf.messagingengine.com designates 66.111.4.224 as permitted sender) DKIM-Signature: v=1; a=rsa-sha1; c=relaxed/relaxed; d=fastmail.com; h= content-transfer-encoding:content-type:date:from:message-id :mime-version:subject:to:x-me-sender:x-me-sender:x-sasl-enc; s= mesmtp; bh=Hb8aUtM0icLtp+y1Bf3IdpuRG/E=; b=BjUu8JUgmPZz+LtfRMnrk J9F2OfONPOSndjyOR9sWe3XCmvgV84c0tEkclOv+VCtI/T2KHHvOnEXs77Om3pc2 JvWEsDFLAyvYmbtkcgGGOtJjSyMWqbAc16as/bZiPgvAD8sbF/mBQH0SU4fNTONT GSSsV86+W2G9niEUKDIYsQ= DKIM-Signature: v=1; a=rsa-sha1; c=relaxed/relaxed; d= messagingengine.com; h=content-transfer-encoding:content-type :date:from:message-id:mime-version:subject:to:x-me-sender :x-me-sender:x-sasl-enc; s=smtpout; bh=Hb8aUtM0icLtp+y1Bf3IdpuRG /E=; b=FCbh42ZvI+SL3A68wIxKf5EJPx0VtHph09kWP9MEd0BhJOG89si4+vFaJ VRHFkqlIXe4+Jnmbb5FjIrFn9yBIY8PzPZGbm8g6dodA4gUe55rPLOSIkx+oFYgB u5KeBs06DJAfSAYHVB8GWxtZ1sldWOB3CwuBzbEWRt4N8NvQ9U= X-ME-Sender: Message-Id: <1479449829.1305485.791811385.14DDFE28@webmail.messagingengine.com> From: Sebastian Gniazdowski To: zsh-workers@zsh.org MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="utf-8" X-Mailer: MessagingEngine.com Webmail Interface - ajax-461bce03 Subject: Possible huge setarrvalue optimization Date: Thu, 17 Nov 2016 22:17:09 -0800 Hello, in params.c / setarrvalue there is code: 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); The point is that the code is also run when doing: a=( a b c d ) a[1]="x" The optimization can be: no allocation of new array when size of output array doesn't change. The problem is that following debug: fprintf( _F, "%d %d\n", pre_assignment_length, post_assignment_length ); Shows "4 5" for the a[1]="x" assignment. Shows the same for a+=( "x" ). If this would be fixed, one could detect that pre_assignment_length == post_assignment_length, and skip allocation, only do: for (r = val; *r;) { /* Give away ownership of the string */ *p++ = *r++; } This would be a huge optimization. Has anyone idea of how the pre_assignment_length / post_assignment_length computation works, and why it's wrong for a[1]="x" ? -- Sebastian Gniazdowski psprint@fastmail.com