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Fri, 19 Mar 2021 19:46:17 -0400 (EDT) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 12.4 \(3445.104.17\)) Subject: Re: run time of math problem From: =?utf-8?Q?Lawrence_Vel=C3=A1zquez?= In-Reply-To: Date: Fri, 19 Mar 2021 19:46:16 -0400 Cc: zsh-users@zsh.org Content-Transfer-Encoding: 7bit Message-Id: References: To: Ray Andrews X-Mailer: Apple Mail (2.3445.104.17) X-Seq: 26583 Archived-At: X-Loop: zsh-users@zsh.org Errors-To: zsh-users-owner@zsh.org Precedence: list Precedence: bulk Sender: zsh-users-request@zsh.org X-no-archive: yes List-Id: List-Help: List-Subscribe: List-Unsubscribe: List-Post: List-Owner: List-Archive: Archived-At: > On Mar 19, 2021, at 7:18 PM, Ray Andrews wrote: > > ... I'd expect the thing to run a teeny bit faster but in fact it > runs about 15% slower. Is that explicable? Does zsh prefer > calculations done in steps with variables for each step? Or is this > just some little anomaly? Things might not optimize every time. Think about how your change affects your algorithm. > for ((level=1; level<100; level++)); do > sum= > remainder=$(( (level - 1.0) / level )) > for ((terms=level; terms; terms--)); do > sum+=$(( remainder**(terms - 1) )) > done > divided=$(( sum * (1.0 / level) )) > echo for level: $level, survival: $divided > done Here, you evaluate "(level - 1.0) / level" 99 times. > Now if I avoid the 'remainder' variable: > > for ((level=1; level<100; level++)); do > sum= > for ((terms=level; terms; terms--)); do > > # 'remainder' calculation done directly here: > sum+=$(( ( (level - 1.0) / level )**(terms - 1) )) > done > divided=$(( sum * (1.0 / level) )) > echo for level: $level, survival: $divided > done Here, you evaluate it 4950 times. vq