jbse | symbolic Java Virtual Machine for automated program analysis | Math library
kandi X-RAY | jbse Summary
kandi X-RAY | jbse Summary
JBSE is a symbolic Java Virtual Machine for automated program analysis, verification and test generation. If you are not sure about what "symbolic execution" is you can refer to the corresponding Wikipedia article or to some textbook. But if you are really impatient, symbolic execution is to testing what symbolic equation solving is to numeric equation solving. While numeric equations, e.g. x^2 - 2 x + 1 = 0, have numbers as their parameters, symbolic equations, e.g. x^2 - b x + 1 = 0 may have numbers or symbols as their parameters. A symbol stands for an infinite, arbitrary set of possible numeric values, e.g., b in the previous example stands for an arbitrary real value. Solving a symbolic equation is therefore equivalent to solving a possibly infinite set of numeric equations, that is, the set of all the equations that we obtain by replacing its symbolic parameters with arbitrary numbers. When solving an equation, be it numeric or symbolic, we may need to split cases: For example, a quadratic equation in one variable may have two, one or zero real solutions, depending on the sign of the discriminant. Solving a numeric equation means following exactly one of the possible cases, while symbolic equation solving may require to follow more than one of them. For example, the x^2 - 2 x + 1 = 0 equation falls in the "zero discriminant" case and thus has one solution, while the x^2 - b x + 1 = 0 equation may fall in any of the three cases depending on the possible values of b: If |b| > 2 the discriminant is greater than zero and the equation has two real solutions, if b = 2 or b = -2 the discriminant is zero and the equation has one real solution. Finally, if -2 < b < 2, the discriminant is less than zero and the equation has no real solutions. Since all the three subsets for b are nonempty any of the three cases may hold. As a consequence, the solution of a symbolic equation is usually expressed as a set of summaries. A summary associates a condition on the symbolic parameters with a corresponding possible result of the equation, where the result can be a number or an expression in the symbols. For our running example the solution produces as summaries |b| > 2 => x = [b + sqrt(b^2 - 4)] / 2, |b| > 2 => x = [b - sqrt(b^2 - 4)] / 2, b = 2 => x = 1, and b = -2 => x = -1. Note that summaries overlap where a combination of parameters values (|b| > 2 in the previous case) yield multiple results, and that the union of the summaries does not span the whole domain for b, because some values for b yield no result. JBSE allows the inputs of a Java program to be either concrete values (usual Java primitive or reference values) or symbols. A symbol stands for an arbitrary primitive or reference value on which JBSE does not make any initial assumption. During the execution JBSE may need to make assumptions on the symbolic inputs, e.g. to decide whether it must follow the "then" or "else" branch of a conditional statement, or to decide whether accessing a field with a symbolic reference yields a value or raises a NullPointerException. In these situations JBSE splits the possible cases and analyzes all of them. In the case of the symbolic reference it first assumes that it is null, and continues the execution by raising the exception. At the end of the execution it backtracks and assumes the opposite, i.e., that the symbolic reference refers to some (nonnull) object. This way JBSE can explore how a Java program behaves when fed with possibly infinite classes of inputs, while testing is always limited in investigating a single behavior a time.
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- Invoke the class loader load class loader
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- Get an array from the given value
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Community Discussions
Trending Discussions on Math
QUESTION
I recently came across this problem:
You are given two strings, s1 and s2, comprised entirely of lowercase letters 'a' through 'r', and need to process a series of queries. Each query provides a subset of lowercase English letters from 'a' through 'r'. For each query, determine whether s1 and s2, when restricted only to the letters in the query, are equal. s1 and s2 can contain up to 10^5 characters, and there are up to 10^5 queries.
For instance, if s1 is "aabcd" and s2 is "caabd", and you are asked to process a query with the subset "ac", then s1 becomes "aac" while s2 becomes "caa". These don't match, so the query would return false.
I was able to solve this in O(N^2) time by doing the following: For each query, I checked if s1 and s2 would be equal by iterating through both strings, one character at a time, skipping the characters that do not lie within the subset of allowed characters, and checking to see if the "allowed" characters from both s1 and s2 match. If at some point, the characters don't match, then the strings are not equal. Otherwise, the s1 and s2 are equal when restricted only to letters in the query. Each query takes O(N) time to process, and there are N queries, for a total of O(N^2) time.
However, I was told that there was a way to solve this faster in O(N). Does anyone know how this might be done?
...ANSWER
Answered 2022-Mar-28 at 11:30The first obvious speedup is to ensure your set membership test is O(1). To do that, there's a couple of options:
- Represent every letter as a single bit -- now every character is an 18-bit value with only one bit set. The set of allowed characters is now a mask with these bits ORed together and you can test membership of a character with a bitwise-AND;
- Alternatively, you can have an 18-value array and index it by character (
c - 'a'would give a value between 0 and 17). The test for membership is then basically the cost of an array lookup (and you can save operations by not doing the subtraction -- instead just make the array larger and index directly by character.
The next potential speedup is to recognize that any character which does not appear exactly the same number of times in both strings will instantly be a failed match. You can count all character frequencies in both strings with a histogram which can be done in O(N) time. In this way, you can prune the search space if such a character were to appear in the query, and you can test for this in constant time.
Of course, that won't help for a real stress-test which will guarantee that all possible letters have a frequency matched in both strings. So, what do you do then?
Well, you extend the above premise by recognizing that for any position of character x in string 1 and some position of that character in string 2 that would be a valid match (i.e the same number of character x appears in both strings up to their respective positions), then the total count of any other character up to those positions must also be equal. For any character where that is not true, it cannot possibly be compatible with character x.
Let's start by thinking about this in terms of a technique known as memoization where you can leverage precomputed or partially-computed information and get a whole lot out of it. So consider two strings like this:
QUESTION
It is a number whose gcd of (sum of quartic power of its digits, the product of its digits) is more than 1. eg. 123 is a special number because hcf of(1+16+81, 6) is more than 1.
I have to find the count of all these numbers that are below input n. eg. for n=120 their are 57 special numbers between (1 and 120)
I have done a code but its very slow can you please tell me to do it in some good and fast way. Is there is any way to do it using some maths.
...ANSWER
Answered 2022-Mar-06 at 18:14The critical observation is that the decimal representations of special numbers constitute a regular language. Below is a finite-state recognizer in Python. Essentially we track the prime factors of the product (gcd > 1 being equivalent to having a prime factor in common) and the residue of the sum of powers mod 2×3×5×7, as well as a little bit of state to handle edge cases involving zeros.
From there, we can construct an explicit automaton and then count the number of accepting strings whose value is less than n using dynamic programming.
QUESTION
I need to calculate the square root of some numbers, for example √9 = 3 and √2 = 1.4142. How can I do it in Python?
The inputs will probably be all positive integers, and relatively small (say less than a billion), but just in case they're not, is there anything that might break?
Related
- Integer square root in python
- Is there a short-hand for nth root of x in Python?
- Difference between **(1/2), math.sqrt and cmath.sqrt?
- Why is math.sqrt() incorrect for large numbers?
- Python sqrt limit for very large numbers?
- Which is faster in Python: x**.5 or math.sqrt(x)?
- Why does Python give the "wrong" answer for square root? (specific to Python 2)
- calculating n-th roots using Python 3's decimal module
- How can I take the square root of -1 using python? (focused on NumPy)
- Arbitrary precision of square roots
Note: This is an attempt at a canonical question after a discussion on Meta about an existing question with the same title.
...ANSWER
Answered 2022-Feb-04 at 19:44math.sqrt()
The math module from the standard library has a sqrt function to calculate the square root of a number. It takes any type that can be converted to float (which includes int) as an argument and returns a float.
QUESTION
I write a mathematical function to be benchmark function in my optimization algorithm.
...ANSWER
Answered 2022-Feb-12 at 13:14In the platform that produces “-4,09139395927863E+154”, the Math.Cos routine is broken. It apparently uses a processor instruction that does not support operands outside [−2−63, +2−63].
Since I do not use C#, here is a C program that reproduces the correct behavior:
QUESTION
In particular, it must work with NaNs as std::copysign does. Similarly, I need a constexpr std::signbit.
ANSWER
Answered 2021-Sep-20 at 19:54If you can use std::bit_cast, you can manipulate floating point types cast to integer types. The portability is limited to the representation of double, but if you can assume the IEEE 754 double-precision binary floating-point format, cast to uint64_t and using sign bit should work.
QUESTION
I'm working on some heavy algorithm, and now I'm trying to make it multithreaded. It has a loop with 2 nested loops:
...ANSWER
Answered 2021-Dec-20 at 09:25A third attempt:
I've taken your code, and at last got it to run properly (in python):
QUESTION
I would like to make the following sequence in R, by using rep or any other function.
ANSWER
Answered 2022-Jan-04 at 15:43Use sequence.
QUESTION
I am trying to achieve a calculation involving geometric progression (split). Is there any effective/efficient way of doing it. The data set has millions of rows. I need the column "Traded_quantity"
Marker Action Traded_quantity 2019-11-05 09:25 0 0 09:35 2 BUY 3 09:45 0 0 09:55 1 BUY 4 10:05 0 0 10:15 3 BUY 56 10:24 6 BUY 8128turtle = 2 (User defined)
base_quantity = 1 (User defined)
...ANSWER
Answered 2022-Jan-22 at 10:09This should work
QUESTION
I want to create a polynomial ring which has float Coefficients like this. I can create with integers but, Floats does not work.
...ANSWER
Answered 2022-Jan-18 at 23:30While I do not have previous experience with this particular (from appearances, rather sophisticated) package Oscar.jl, parsing this error message tells me that the function you are trying to call is being given a BigFloat as input, but simply does not have a method for that type.
At first this was a bit surprising given that there are no BigFloats in your input, but after a bit of investigation, it appears that the culprit is the following
QUESTION
I don't know if this is possible, but I am trying to take the image of a custom outdoor football field layout and have the players' GPS coordinates correspond to the image xand y position. This way, it can be viewed via the app to show the players' current location on the field as a sort of live tracking.
I have also looked into this Convert GPS coordinates to coordinate plane. The problem is that I don't know if this would work and wanted to confirm beforehand. The image provided in the post was for indoor location, and it was from 11 years ago.
I used Location and Google Maps packages for flutter. The player's latitude and longitude correspond to the actual latitude and longitude that the simulator in the android studio shows when tested.
The layout in question and a close comparison to the result I am looking for.
Any help on this matter would be appreciated highly, and thanks in advance for all the help.
Edit:
After looking more at the matter I tried the answer of this post GPS Conversion - pixel coords to GPS coords, but it wasn't working as intended. I took some points on the image and the correspond coordinates, and followed the same logic that the answer used, but reversed it to give me the actual image X, Ypositions.
The formula that was given in the post above:
...ANSWER
Answered 2022-Jan-12 at 08:20First of All, Yes you can do this with high accuracy if the GPS coordinates are accurate.
Second, the main problem is rotation if the field are straight with lat lng lines this would be easy and straightforward (no bun intended).
The easy way is to convert coordinate to rotated image similar to the real field then rotated every X,Y point to the new straight image. (see the image below)
Here is how to rotate x,y knowing the angel:
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You can use jbse like any standard Java library. Please include the the jar files in your classpath. You can also use any IDE and you can run and debug the jbse component as you would do with any other Java program. Best practice is to use a build tool that supports dependency management such as Maven or Gradle. For Maven installation, please refer maven.apache.org. For Gradle installation, please refer gradle.org .
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