作者gais123 (Flying翔)
看板Cad_Cae
標題[請益] Comsol 虛擬記憶體 計算速度
時間Mon Apr 15 17:03:40 2019
小弟目前使用comsol計算3維的流體模擬
目前的case的網格數約50萬，自由度達到460萬，大概需要7天以上才會跑完
我仔細觀察工作管理員上CPU的使用率，發現comsol偶爾吃60幾%，偶爾吃不到10%
我在想是不是CPU不到10%的時候，是因為comsol需要把資料暫存在Ram上，但我看comsol吃的Ram有分成實體記憶體(左)和虛擬記憶體(右)，圖的最下面
因為虛擬記憶體似乎是吃C槽硬碟，我的C槽是SSD，並且去系統看我虛擬記憶體的配置，如下圖
想問手動增加或減少虛擬記憶體的配置，對於comsol計算速度會不會增加呢?
若會增加速度，那增加的程度會很多嗎?
目前因為正在跑3維case，無法中斷comsol來測試虛擬記憶體，想說在板上詢問有高手是否有類似經驗
謝謝
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推 Loserme5566: 一定需要用迭代求解器嗎？用直接求解器我跑共軛層流5 04/18 23:01
→ Loserme5566: 0萬格點，i7大約6.7小時 04/18 23:01
→ Loserme5566: 原廠使用手冊也有說情況允許，直接求解器比較省時 04/18 23:02
→ Loserme5566: 虛擬記憶體這點我也想多了解，等待其他大大現身說法 04/18 23:03
→ gais123: 請教L大是如何設定直接求解器呢?我是直接用內建的求解器 04/19 14:26
→ gais123: ，但裡面有很多，不曉得如何只設定直接求解器 04/19 14:26
→ gais123: 
04/19 14:28
04/19 14:28推 sshyu954: 花錢買ram, 給他加到最大， 用pardiso解 05/30 13:56
... <看更多>
虛擬記憶體 計算 在 [課業] 計算機概論- 虛擬記憶體計算- 看板Examination 的推薦與評價
在計算機概論課本上看到的兩題練習題，不過是英文的，所以我也用英文回答。
我對這些東西不是很了解，怕翻成中文以後會翻錯，所以直接貼原文上來，保險一點。
題目(一)：;A multiprogramming operating system uses paging.
The available memory is 60 MB divided into 15 frames, each of 4 MB.
Program A needs 13 MB. Program B needs 12 MB. Program C needs 27 MB.
Q1: How many frames are used by program A, B and C?
My answer -> Program A use 4 frames, program B use 3 frames,
and program C use 7 frames.
Q2: How many frames are unused?
My answer -> 15-(4+3+7) = 1. So 1 frame is unused.
Q3: What is the total memory wasted?
My answer -> 60 - (13+12+27) = 8. So 8 MB of memory is wasted.
Q4: What percentage of memory is wasted?
My answer -> 8/60 = 13.3% (approximately). So 13.3% of memory is wasted.
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題目(二): An operating system uses virtual memory but requires the whole
program to be in physical memory during execution (no paging or
segmentation). The size of physical memory is 100 MB.
The size of virtual memory is 1 GB.
Q5: How many programs of size 10 MB can be run concurrently by this
operating system?
My answer -> Since programs have to be in physical memory during execution,
then 100 MB/10 MB = 10 programs can be run concurrently by this
operating system.
Q6: How many of them can be in memory at any time?
My answer -> 100 MB / 10 MB = 10 programs can be in memory at any time.
Q7: How many of them must be on disk?
My answer -> 10 programs are in physical memory, and the size of virtual
memory is 1024 MB, which means 102 programs can be stored in
disk + physical memory. So 102-10 = 92 programs must be on disk.
需要大家幫忙糾正錯誤，謝謝。
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※ 編輯: editorer (59.102.180.162), 12/04/2014 18:31:41
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