For the record, this is homework.
I have a problem, where I have a processor that uses 32 bit virtual addresses and 32 bit physical addresses, with 4Kb pages and a linear page table.
I am given the following assembly instruction (MIPS32)
lw $t0, 0x34c8($zero)
Since, this processor uses 4Kb pages, the offset in the virtual address is 12 bits long, and therefore the last nibble in the address is the VPN (3). Using that to query the page table, I found that the PTE is an empty entry:
VPN | Dirty | Present | PPN
----------------------------
0 | 1 | 0 | 0x1
----------------------------
1 | 0 | 1 | 0x0
----------------------------
2 | 1 | 1 | 0x6
----------------------------
3 | - | 0 | -
----------------------------
4 | 0 | 1 | 0x4
----------------------------
5 | 0 | 1 | 0x2
----------------------------
6 | 0 | 1 | 0x7
----------------------------
7 | 0 | 1 | 0x3
How do I find the physical address, then? I'm told all physical pages in memory are in use, but I don't know if that helps. Am I supposed to assume the PPN is going to be 0x5, since that's the only "missing" page number not in the table?
Thanks.
Related
I am looking this source codes to use Ymodem protocole,
https://github.com/STMicroelectronics/STM32CubeF4/blob/master/Projects/STM324xG_EVAL/Applications/IAP/IAP_Main/inc/ymodem.h
But I've a question about that,
Line 65 says to us as in below:
/* /-------- Packet in IAP memory ------------------------------------------\
* | 0 | 1 | 2 | 3 | 4 | ... | n+4 | n+5 | n+6 |
* |------------------------------------------------------------------------|
* | unused | start | number | !num | data[0] | ... | data[n] | crc0 | crc1 |
* \------------------------------------------------------------------------/
* the first byte is left unused for memory alignment reasons
According to this informaton PACKET_DATA_INDEX define 4. But I dont understand this because in the Ymodem includes data in 3th byte, why we choose the 4th byte or SOH is the 0th index of the frame, why we get this as a 1
Let's say we have the following dataset
Label | Features |
-----------------------------------
Age | Size | Weight | shoeSize |
20 | 180 | 80 | 42 |
40 | 173 | 56 | 38 |
as i know features in machine learning should be normalized and the ones mentioned above can be normalized really good. but what if i want to extend the feature list for for example the following features
| Gender | Ethnicity |
| 0 | 1 |
| 1 | 2 |
| 0 | 3 |
| 0 | 2 |
where the Gender values 0 and 1 are for female and male. and the Ethnicity values 1, 2 and 3 are for asian, hispanic and european. since these values reference types i am note sure if they can be normalized.
if they can not be normalized how can i handle mixing values like the size with types like the enthnicity.
I'm having trouble expressing my question in words, but I think I can express it visually quite simply. Storing the string abcd, is the difference between Big and Little Endian this:
memory address | 0 | 1 | 2 | 3 | 4 | 5 | 6 | ...
little endian | d | c | b | a |
big endian | a | b | c | d |
Or this:
memory address | 0 | 1 | 2 | 3 | 4 | 5 | 6 | ...
little endian | d | c | b | a |
big endian | a | b | c | d |
My attempt in words: does "endianness" refer to the ordering of bytes within a specific memory "array", where in both cases the array begins at the same point in memory, or does it refer to both the ordering and the actual array used?
Endianness refers to the ordering of bytes used to store a single multi-byte numerical value. The "big endian" system in your second image is storing 4-byte integers unaligned, which no system would normally do.
I'm looking for a concept for doing a Gödel numbering for bit strings, i.e. for arbitrary binary data.
Approach 1 (failing): Simply interpret the binary data as data of an unsigned integer.
This fails, because e.g. the two different strings "01" and "001" both represent the same integer 1.
Is there a standard way of doing this? Is 0 usually included or excluded from the Gödel numbering?
The original Gödel numbering used prime numbers and unique encoding of symbols. If you want to do it for strings consisting of "0" and "1", you need positive codes for "0" (say 1) and "1" (say 2). Then numbering of "01" is
21 * 32
while numbering of "001" is
21 * 31 * 52
For longer strings use next prime numbers. However, note that Gödel numbering goals did not include any practical considerations, he simply needed numbering as a tool in the proof of his theorem. In practice for fairly short strings you will exceed range of integers in your language, so you need to use either a language with arbitrary large integers built-in (like Scheme) or a library supporting bignums in language without them built-in.
A super simple solution is to prepend a 1 to the binary data and then interpret the result as an unsigned integer value. This way, no 0-digits get lost at the left side of the bit string.
Illustration how well this works:
One obvious way to order bit strings is to order them first by length and then lexicographically:
+------------+
| bit string |
+------------+
| ε |
| 0 |
| 1 |
| 00 |
| 01 |
| 10 |
| 11 |
| 000 |
| 001 |
| 010 |
| 011 |
| 100 |
| 101 |
| 110 |
| ... |
+------------+
(ε denotes the empty string with no digits.)
Now we add an index number n to this table, starting with 1, and then look at the binary representation of the index number n. We will make a nice discovery there:
+------------+--------------+-------------+
| bit string | n in decimal | n in binary |
+------------+--------------+-------------+
| ε | 1 | 1 |
| 0 | 2 | 10 |
| 1 | 3 | 11 |
| 00 | 4 | 100 |
| 01 | 5 | 101 |
| 10 | 6 | 110 |
| 11 | 7 | 111 |
| 000 | 8 | 1000 |
| 001 | 9 | 1001 |
| 010 | 10 | 1010 |
| 011 | 11 | 1011 |
| 100 | 12 | 1100 |
| 101 | 13 | 1101 |
| 110 | 14 | 1110 |
| ... | ... | ... |
+------------+--------------+-------------+
This works out surprisingly well, because the binary representation of n (the index of each bit string when ordering in a very obvious way) is nothing else than a 1 prepended to the original bit string and then the whole thing interpreted as an unsigned integral value.
If you prefer a 0-based Goedel numbering, then subtract 1 from the resulting integer value.
Conversion formulas in pseudo code:
// for starting with 1
n_base1 = integer(prepend1(s))
s = removeFirstDigit(bitString(n_base1))
// for starting with 0
n_base0 = integer(prepend1(s)) - 1
s = removeFirstDigit(bitString(n_base0 + 1))
I'm rolling the following:
Rails 3.2.9
Highcharts
State Machine
I've got an irregular set of data that represents the change of state of hundreds of linux boxes. Each box checks into a central ping server every two minutes.
Every time a device heartbeats, the ping server checks if the device's current state is offline and if so, changes the state to online and sets the heartbeat table's online col to true and inserts the time this happened.
On the ping server, we have a cron that runs a rake task every 5 minutes. This finds all devices with a heartbeat less than the time now minus 5 minutes.
If it discovers a device is offline, it sets the device state to offline and marks to heartbeat table with the time of the last heartbeat and a 0.
We've been doing this for a while and it seems like an efficient way to store the uptime data without creating a row for 500 devices every 5 minutes.
The table looks a little like this:
+---------------------+--------+--------+
| created_at | dev_id | online |
+---------------------+--------+--------+
| 2012-10-08 16:29:16 | 2345 | 0 |
| 2012-11-21 16:40:22 | 2345 | 1 |
| 2012-11-03 19:15:00 | 2345 | 0 |
| 2012-11-08 09:15:01 | 2345 | 1 |
| 2012-11-08 09:18:03 | 2345 | 0 |
| 2012-11-09 17:57:22 | 2345 | 1 |
| 2012-12-09 13:57:23 | 2345 | 0 |
| 2012-12-09 14:57:25 | 2345 | 1 |
| 2012-12-09 15:00:30 | 2345 | 0 |
| 2012-12-09 15:57:31 | 2345 | 1 |
| 2012-12-09 16:07:35 | 2345 | 0 |
| 2012-12-09 16:37:38 | 2345 | 1 |
| 2012-12-09 17:57:40 | 2345 | 0 |
+---------------------+--------+--------+
Following Ryan Bate's fantastic Railscast on Highcharts, I can create a line graph of this data with irregular intervals.
The chart and data series
Following this example:
http://www.highcharts.com/demo/spline-irregular-time
And using a data series something like this:
= #devices.heartbeats.map { |o| o.online == true ? 1 : 0 }
It was plotting the line graph pretty nicely.
Where I'm stuck
The graph finishes at the last time it checked in and I need the graph to show a point at Now. In Ryan's example, he maps a zero to a date if there's no value. I can't translate this part.
I'm trying to achieve a graph like the stack bar chart but can't get the data sorted.
http://www.highcharts.com/demo/bar-stacked
How can I format my query so I get the data until Now as well as each individual point so I can create such a graph?