From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from lists.gentoo.org (pigeon.gentoo.org [208.92.234.80]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by finch.gentoo.org (Postfix) with ESMTPS id 865ED139694 for ; Tue, 30 May 2017 08:23:52 +0000 (UTC) Received: from pigeon.gentoo.org (localhost [127.0.0.1]) by pigeon.gentoo.org (Postfix) with SMTP id 90ABDE0EBC; Tue, 30 May 2017 08:22:57 +0000 (UTC) Received: from mail-wm0-x22b.google.com (mail-wm0-x22b.google.com [IPv6:2a00:1450:400c:c09::22b]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by pigeon.gentoo.org (Postfix) with ESMTPS id 210E4E0EB1 for ; Tue, 30 May 2017 08:22:52 +0000 (UTC) Received: by mail-wm0-x22b.google.com with SMTP id d127so87109430wmf.0 for ; Tue, 30 May 2017 01:22:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=googlemail.com; s=20161025; h=date:from:to:subject:message-id:in-reply-to:references:mime-version :content-transfer-encoding; bh=BnwDGWO8dfbZ8aWclX7cujbdST8Lv1fwgd8c821OYd4=; b=i8lbzflmAhHT9iiKhdRI3qKjI03qPIkhXNs5D2M0kzDrJhPeH/qAgdIU8ikgy8Ce8T SwjSlzSrklj2DBNWx0C8n6YjF9eMBcJkPn8oEu9od9WsyhE+QWBcrtumPCvpzkp4xxML upwget51E25PTOubeIoat8LKWpMDXYajOXNSdbJXRxvRtX/T37e3v3oXW7wj1Q9jaavp KsJ2viEyqiRhS1enq+gQCfDdJ2IDzuXH85HULqlk1uydEa7ns5w5GLL9VhFjXSLavnoU /BjoWi2fQbBP67igyVsQQItBckgUYk2a1h6SnV3T5Iq/L+RXD1OiDkCex4Ofgfk8zST4 Y3uA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:subject:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=BnwDGWO8dfbZ8aWclX7cujbdST8Lv1fwgd8c821OYd4=; b=UmQKWMe8wZW96+rJrfrrKMrGFiOTe/vaVqsR2zUdnYLu7sbzlQfStJFFCFI2CbqAp8 hKIAfXB1MLZl4N1XFg7SaJeqWi6d7p7q21534h2ML9P6ucrKFdzhjzS9GDKUrT2GwWQ3 7Xp1GD197ZGirWHjkhlyQiP3Otf6rQ16ftbREMbnZefbP4oo/T5TfTN/g4CRq1a5SRKE yDsGIRiZyoUd2usKu3uOQ+dyeML9nKFwILdTOQns3TbZTb9fv/BI3tlm7VuYIKG5AKvC pyWRDj2CHri3DLC9ilpaRmISyEl0aWNzT5xI0HVekVDRfypgLkA566SYl66DM0eORTA/ Avgg== X-Gm-Message-State: AODbwcAWgNEP46PBYVXChT6O4YQ4GE68N7AbDrKKW9ALEIRgqle1sa6B uAo8+oc2TcuHoz7u X-Received: by 10.28.21.7 with SMTP id 7mr780601wmv.39.1496132569777; Tue, 30 May 2017 01:22:49 -0700 (PDT) Received: from snowblower (cpc4-broo7-2-0-cust35.14-2.cable.virginm.net. [82.8.215.36]) by smtp.gmail.com with ESMTPSA id f70sm20551352wmd.25.2017.05.30.01.22.49 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 30 May 2017 01:22:49 -0700 (PDT) Date: Tue, 30 May 2017 09:22:45 +0100 From: Ciaran McCreesh To: gentoo-dev@lists.gentoo.org Subject: Re: [gentoo-dev] [RFC] Forced/automatic USE flag constraints (codename: ENFORCED_USE) Message-ID: <20170530092245.681d4aeb@snowblower> In-Reply-To: <20170530094245.40e1cf64@gentoo.org> References: <1496071993.31087.1.camel@gentoo.org> <20170529200037.2559f80a@gentoo.org> <1496093035.12795.3.camel@gentoo.org> <20170530094245.40e1cf64@gentoo.org> X-Mailer: Claws Mail 3.13.0 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-Id: Gentoo Linux mail X-BeenThere: gentoo-dev@lists.gentoo.org Reply-to: gentoo-dev@lists.gentoo.org MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Archives-Salt: d9aa1f6b-41db-4ca8-9a06-7ac778e63e77 X-Archives-Hash: 8789bd8bbb4643944495de9223d97d42 On Tue, 30 May 2017 09:42:45 +0200 Alexis Ballier wrote: > Oh crap, this requires to solve SAT. The main problem would not be solving SAT, in this case. The problem is providing the right answer when not enough information is given. Spitting out a resolution which satisfies every dependency isn't typically that difficult. Spitting out a resolution which doesn't just turn off all your use flags and uninstall most of your programs is the hard part. > Not hard as in you need a Ph.D. in algorithms to solve it but the > kind of hardness almost every cryptographic algorithm used today, and > in the foreseeable future, relies on. Hrm, you're a bit off, there. SAT solving in practice isn't usually that bad unless either your inputs are huge or they're deliberately crafted to be ultra-nasty. Being NP-complete just means that instances that will hit exponential behaviour exist, not that those instances will occur in the application area you care about. -- Ciaran McCreesh