From nobody Thu Dec 25 19:30:09 2025 Received: from mail-pl1-f176.google.com (mail-pl1-f176.google.com [209.85.214.176]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 20A7BFC19 for ; Sat, 13 Jan 2024 03:14:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="IAUOSmEG" Received: by mail-pl1-f176.google.com with SMTP id d9443c01a7336-1d48a8ed85bso16563995ad.0 for ; Fri, 12 Jan 2024 19:14:17 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1705115657; x=1705720457; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=JLymtwc9H5yinl0KgXVhcfE0CrkBjQrFclqsS4J1/G8=; b=IAUOSmEGwZd0bCq/GfJo26LS+sqAGPI428epKv7lh1BCLfLNNNsfnpDJfqz3sSabNc twZP3ih2yuuhekhloQ4tBipgz6zp7mk5Szg4fnH7tjmdwT2KVoA30kNPE1Q9pszn92Je KZ9gRx7Tk+lYLv474th1+ZmA1ueGfOc4JNYfYBnkAz6KsYZmuSPQBcvgCUR3P+yzP3oL S67Mvpm+1JX/L0cKQbn+mnudjeIbhXcPogdKlaqkM2Hb9rfEZi8CoAFHx3eqFWZs67gN rsJGguZR+dkhhyFuFBxGCEYQY+i6SI7nyKf3cdrnb6HsLouKPFOYJ3k20bnHieEykzqL m3DQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1705115657; x=1705720457; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=JLymtwc9H5yinl0KgXVhcfE0CrkBjQrFclqsS4J1/G8=; b=CR/ddJXReF7Br63+4t9dAmOsv/JiYIpDbfTESnOSjbLA60cLMx2m/vGazXRL7+p/m0 nw94TZon9S06esrRJT/coEvg7u/k0Ew5ajwq/wQfff0u4tbk0k6rirQFau7M/lyfya8m yAaLXJR9YE2fBuxbbhQKHM6T7WYHsLmiJaY66quPCX6Kv6ZYrYVmPsV83txQK6Wj0h+2 P0571oa5CQJaYFbyXr/K8lUh9eDjGMgV2EIruRqn+WJFQ49/O1lo8Oj4ZTQdAIAi51Zg iA/V/FNJgRIoROyyAtUavCdmejxXG5Jk7/6Ay13YwyNDQbp10tfIOqmScfpf5GBvC9LH OWkA== X-Gm-Message-State: AOJu0YyoPPY4DkOQZCjm3/XGqQzc18zaYLouUoITGtDTvH075prCUC78 DNaeICiMe+MqdhE1LGI5rQxLQPZcUI8= X-Google-Smtp-Source: AGHT+IFPg72wcirR0Y8jLSTri8j94yjlsKKkNkkehTPocv2Lf+Jh/Ght75ZG+1mZvCI5tF/rGWCcOw== X-Received: by 2002:a17:902:c194:b0:1d4:be1e:f197 with SMTP id d20-20020a170902c19400b001d4be1ef197mr3958543pld.1.1705115657246; Fri, 12 Jan 2024 19:14:17 -0800 (PST) Received: from localhost.localdomain ([140.116.154.65]) by smtp.gmail.com with ESMTPSA id e2-20020a170902f1c200b001d3c3d486bfsm3912551plc.163.2024.01.12.19.14.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 12 Jan 2024 19:14:16 -0800 (PST) From: Kuan-Wei Chiu To: akpm@linux-foundation.org Cc: lkml@sdf.org, jserv@ccns.ncku.edu.tw, linux-kernel@vger.kernel.org, Kuan-Wei Chiu Subject: [PATCH 1/2] lib/sort: Optimize heapsort for equal elements in sift-down path Date: Sat, 13 Jan 2024 11:13:51 +0800 Message-Id: <20240113031352.2395118-2-visitorckw@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20240113031352.2395118-1-visitorckw@gmail.com> References: <20240113031352.2395118-1-visitorckw@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Currently, when searching for the sift-down path and encountering equal elements, the algorithm chooses the left child. However, considering that the height of the right subtree may be one less than that of the left subtree, selecting the right child in such cases can potentially reduce the number of comparisons and swaps. For instance, when sorting an array of 10,000 identical elements, the current implementation requires 247,209 comparisons. With this patch, the number of comparisons can be reduced to 227,241. Signed-off-by: Kuan-Wei Chiu --- lib/sort.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/lib/sort.c b/lib/sort.c index b399bf10d675..fe4efd4a1410 100644 --- a/lib/sort.c +++ b/lib/sort.c @@ -262,7 +262,7 @@ void sort_r(void *base, size_t num, size_t size, * average, 3/4 worst-case.) */ for (b =3D a; c =3D 2*b + size, (d =3D c + size) < n;) - b =3D do_cmp(base + c, base + d, cmp_func, priv) >=3D 0 ? c : d; + b =3D do_cmp(base + c, base + d, cmp_func, priv) > 0 ? c : d; if (d =3D=3D n) /* Special case last leaf with no sibling */ b =3D c; =20 --=20 2.25.1