bf | Brainfuck interpreter in Rust | Interpreter library
kandi X-RAY | bf Summary
kandi X-RAY | bf Summary
This is a basic Brainfuck interpreter I wrote to practice Rust programming.
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QUESTION
Assembly novice here. I've written a benchmark to measure the floating-point performance of a machine in computing a transposed matrix-tensor product.
Given my machine with 32GiB RAM (bandwidth ~37GiB/s) and Intel(R) Core(TM) i5-8400 CPU @ 2.80GHz (Turbo 4.0GHz) processor, I estimate the maximum performance (with pipelining and data in registers) to be 6 cores x 4.0GHz = 24GFLOP/s. However, when I run my benchmark, I am measuring 127GFLOP/s, which is obviously a wrong measurement.
Note: in order to measure the FP performance, I am measuring the op-count: n*n*n*n*6 (n^3 for matrix-matrix multiplication, performed on n slices of complex data-points i.e. assuming 6 FLOPs for 1 complex-complex multiplication) and dividing it by the average time taken for each run.
Code snippet in main function:
...ANSWER
Answered 2022-Mar-25 at 19:331 FP operation per core clock cycle would be pathetic for a modern superscalar CPU. Your Skylake-derived CPU can actually do 2x 4-wide SIMD double-precision FMA operations per core per clock, and each FMA counts as two FLOPs, so theoretical max = 16 double-precision FLOPs per core clock, so 24 * 16 = 384 GFLOP/S. (Using vectors of 4 doubles, i.e. 256-bit wide AVX). See FLOPS per cycle for sandy-bridge and haswell SSE2/AVX/AVX2
There is a a function call inside the timed region, callq 403c0b <_Z12do_timed_runRKmRd+0x1eb> (as well as the __kmpc_end_serialized_parallel stuff).
There's no symbol associated with that call target, so I guess you didn't compile with debug info enabled. (That's separate from optimization level, e.g. gcc -g -O3 -march=native -fopenmp should run the same asm, just have more debug metadata.) Even a function invented by OpenMP should have a symbol name associated at some point.
As far as benchmark validity, a good litmus test is whether it scales reasonably with problem size. Unless you exceed L3 cache size or not with a smaller or larger problem, the time should change in some reasonable way. If not, then you'd worry about it optimizing away, or clock speed warm-up effects (Idiomatic way of performance evaluation? for that and more, like page-faults.)
- Why are there non-conditional jumps in code (at 403ad3, 403b53, 403d78 and 403d8f)?
Once you're already in an if block, you unconditionally know the else block should not run, so you jmp over it instead of jcc (even if FLAGS were still set so you didn't have to test the condition again). Or you put one or the other block out-of-line (like at the end of the function, or before the entry point) and jcc to it, then it jmps back to after the other side. That allows the fast path to be contiguous with no taken branches.
- Why are there 3 retq instances in the same function with only one return path (at 403c0a, 403ca4 and 403d26)?
Duplicate ret comes from "tail duplication" optimization, where multiple paths of execution that all return can just get their own ret instead of jumping to a ret. (And copies of any cleanup necessary, like restoring regs and stack pointer.)
QUESTION
I'm doing a linux online course but im stuck with a question, you can find the question below.
You will get three files called a.bf, b.bf and c.bf. Merge the contents of these three files and write it to a new file called abc.bf. Respect the order: abc.bf must contain the contents of a.bf first, followed by those of b.bf, followed by those of c.bf.
Example Suppose the given files have the following contents:
a.bf contains +++.
b.bf contains [][][][].
c.bf contains <><><>.
The file abc.bf should then have
...ANSWER
Answered 2022-Mar-26 at 13:39echo -n "$(cat a.bf)$(cat b.bf)$(cat c.bf)" > abc.bf
- echo
-nwill not output trailing newlines
QUESTION
Up until Linux 5.8 CAP_SYSADMIN was required to load any but the most basic BPF program. The recently introduced CAP_BPF is a welcome addition as it allows to run software leveraging BPF with less privileges.
Certain types of BPF programs can access packet data. The pre-4.7 way of doing it is via bpf_skb_load_bytes() helper. As the verifier got smarter, it became possible to perform "direct packet access", i.e. to access packet bytes by following pointers in the context structure. E.g:
ANSWER
Answered 2022-Mar-09 at 10:00To make direct packet accesses in your program, you will need CAP_PERFMON in addition to CAP_BPF. I'm not aware of any way around it.
Why?
Because of Spectre vulnerabilities, someone able to perform arithmetic on unbounded pointers (i.e., all except stack and map value pointers) can read arbitrary memory via speculative out-of-bounds loads.
Such operations thus need to be forbidden for unprivileged users. Allowing CAP_BPF users to perform those operations would essentially give read access to arbitrary memory to CAP_BPF. For those reasons, I doubt this limitation will be lifted in the future.
QUESTION
I have a few lists
...ANSWER
Answered 2022-Feb-10 at 12:59Have a look at itertools.combinations. It returns all possible combinations of a given length for a given iterable. You'll have to loop over all possible lengths.
QUESTION
It seems I need some help with resizing the BMP image when the zoom factor is less than 1. You can see the most crucial part of my code below. The variable f in the code is the zoom factor. It seems logical to me but it works improperly. - this is the image I need to resize (to make it even smaller). - and this is the result picture which doesn't look properly. I think I failed in uploading that here, but it looks like a small green square without any white center at all.
Moreover, I tried to resize one more image - this beautiful smiley: And the result was rather unexpected:
This makes me think that there's a problem with the for-cycles, though it seems completely logical to me.
And this is how the BMP is organized.
...ANSWER
Answered 2022-Jan-23 at 22:36I assume you want to shrink the image by skipping rows and columns using the variables w, h, and diff. For instance, if we set the
scaling factor f to 0.5, diff is assigned to 1, and every other
rows/columns will be skipped to scale the image by 0.5x.
Then there are two crutial issues in the loop with i and j:
- You are resetting
winif(w==diff){ w=0; }just afterw++;. Thenwkeeps being 0 and no columns are skipped. - You are putting the
if(h==0){condition in outer block. Then the pixels are not read while h==0. In order to shrink the image, you need to keep on reading every pixels regardless of the condition, and write the pixel if the conditions meet.
Then the loop will be improved as:
QUESTION
I am looking for finding a method to find the association between words in the table (or list). In each cell of the table, I have several words separated by ";".
lets say I have a table as below; some words are 'af' or 'aa' belong to one cell.
...ANSWER
Answered 2022-Jan-17 at 20:11I am not sure if you have something like the approach below in mind. It is basically a custom function which we use in a nested purrr::map call. The outer call loops over the number of pairs: 2,3, 4 and the inner call uses combn to create all possible combinations as input and uses the custom function to create the desired output.
QUESTION
I have inherited a simulation program to extend with new features. The original was written as an Applet using the AWT library for graphics. Before adding the new features I want to adapt the program to the desktop and use JavaFX instead of AWT.
The simulation paints hundreds or thousands of objects dozens of times per second, then erases them and repaints them at new locations, effectively animating them. I am using a Canvas object for that part of the UI. Erasing is done by repainting the object with the background color. What I am seeing though is that erasing objects is incomplete. A kind of "halo" gets left behind though.
The following program illustrates the problem. Clicking the "Draw" button causes it to draw a few hundred circles on the Canvas using the foreground color. After drawing, clicking the button again will erase the circles by re-drawing them in the background color. Multiple cycles of draw/erase will build up a visible background of "ghost" images.
...ANSWER
Answered 2022-Jan-08 at 18:42For expedience, note the difference between fillOval and strokeOval() in the GraphicsContext. You can conditionally erase the outline in drawCircles() as a function of a suitable boolean value:
QUESTION
I am trying to build a plugin for a Minecraft Spigot server that ultimately I would like to be able to communicate over serial with things connected to my PC (server is running locally on the PC as well).
I have been able to build and run the plugin and manipulate player/blocks in the game so I know the build process for my base plugin is working. My trouble started when I began trying to include an extra dependency: jSerialComm
I added the dependency entry in my pom.xml file:
...ANSWER
Answered 2021-Dec-31 at 16:46Even if the JAR is present in your plugin, the classes of the JAR are not loaded in the classpath and Spigot cannot access the classes.
You can use a plugin, such as the maven-shade-plugin, which copies all classes from your API-JAR to your Plugin-JAR.
First, set the scope from provided to compile.
QUESTION
With Python, I wanted to format a string of hex characters:
- spaces between each byte (easy enough):
2f2f->2f 2f - line breaks at a specified max byte width (not hard):
2f 2f 2f 2f 2f 2f 2f 2f\n - address ranges for each line (doable):
0x7f8-0x808: 2f 2f 2f 2f 2f 2f 2f 2f\n - replace large ranges of sequential
00bytes with:... trimmed 35 x 00 bytes [0x7 - 0x2a] ...... it was at this point that I knew I was doing some bad coding. The function got bloated and hard to follow. Too many features piled up in a non-intuitive way.
Example output:
...ANSWER
Answered 2021-Dec-23 at 11:16I would suggest to not start a "trimmed 00 bytes" series in the middle of an output line, but only apply this compacting when it applies to complete output lines with only zeroes.
This means that you will still see non-compacted zeroes in a line that also contains non-zeroes, but in my opinion this results in a cleaner output format. For instance, if a line would end with just two 00 bytes, it really does not help to replace that last part of the line with the longer "trimmed 2 x 00 bytes" message. By only replacing complete 00-lines with this message, and compress multiple such lines with one message, the output format seems cleaner.
To produce that output format, I would use the power of regular expressions:
to identify a block of bytes to be output on one line: either a line with at least one non-zero, or a range of zero bytes which either runs to the end of the input, or else is a multiple of the "byte width" argument.
to insert spaces in a line of bytes
All this can be done through iterations in one expression:
QUESTION
First of all, this question can be a duplicate but the question doesnt have enough information to solve the problem.
I have two windows in my native Win32 application. The first is a layered window with WS_EX_NOACTIVATE extended style and the second is a normal window. I want the layered one to be non-activatable. The problem is that, when I have two window in the same application, the layered one which must be non-activatable, gets activated when switching between them. But there is no problem when switching between two external windows, one being not belong to my application. How can I solve this problem? Or Can I solve that? Is there anything I missed? The following is a minimal reproducable example (didn't include any error checking for minimality.) Thank you for taking time.
ANSWER
Answered 2021-Dec-21 at 18:32Although I still don't understand the cause of the problem, with the help of @IInspectable's guidance and documentation, I was able to prevent the window from being activated by processing the WM_MOUSEACTIVATE message. The updated window procedure is as follows.
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