arXiv subjects

Zhengjun Cao

Publications and source records attributed to Zhengjun Cao.

26 records · Page 2Linked to original sources

arXiv2014

Remarks on AKS Primality Testing Algorithm and A Flaw in the Definition of P

We remark that the AKS primality testing algorithm [Annals of Mathematics 160 (2), 2004] needs about 1,000,000,000 G (gigabyte) storage space for a number of 1024 bits. The requirement is very hard to meet. The complexity class P which contains all decision problems that can be solved by a deterministic Turing machine using a polynomial amount of computation time, is generally believed to be ``easy". We point out that the time is estimated only in terms of the amount of arithmetic operations. It does not comprise the time for reading and writing data on the tape in a Turing machine. The flaw makes some deterministic polynomial time algorithms impractical, and humbles the importance of P=NP question.

cs.CC↗

arXiv2014

A Fast String Matching Algorithm Based on Lowlight Characters in the Pattern

We put forth a new string matching algorithm which matches the pattern from neither the left nor the right end, instead a special position. Comparing with the Knuth-Morris-Pratt algorithm and the Boyer-Moore algorithm, the new algorithm is more flexible to pick the position for starting comparisons. The option really brings it a saving in cost.

cs.DS↗

arXiv2013

Ordered Probability Mass Function

Suppose that in the four tests Alice's scores are 90, 95, 85, 90, and Bob's scores are 85, 95, 90, 90. How to evaluate their scores? In this paper, we introduce the concept of ordered probability mass function which can be used to find a probability mass function with smaller variance. More interestingly, we can use it to distinguish sequences of positive numbers statistically.

cs.DM↗

arXiv2013

On Two Conversion Methods of Decimal-to-Binary

Decimal-to-binary conversion is important to modern binary computers. The classical method to solve this problem is based on division operation. In this paper, we investigate a decimal-to-binary conversion method based on addition operation. The method is very easily implemented by software. The cost analysis shows that the latter is more preferable than the classical method. Thus the current Input/Output translation hardware to convert between the internal digit pairs and the external standard BCD codes can be reasonably removed.

cs.OH↗

arXiv2011

Note on fast division algorithm for polynomials using Newton iteration

The classical division algorithm for polynomials requires $O(n^2)$ operations for inputs of size $n$. Using reversal technique and Newton iteration, it can be improved to $O({M}(n))$, where ${M}$ is a multiplication time. But the method requires that the degree of the modulo, $x^l$, should be the power of 2. If $l$ is not a power of 2 and $f(0)=1$, Gathen and Gerhard suggest to compute the inverse,$f^{-1}$, modulo $x^{\lceil l/2^r\rceil}, x^{\lceil l/2^{r-1}\rceil},..., x^{\lceil l/2\rceil}, x^l$, separately. But they did not specify the iterative step. In this note, we show that the original Newton iteration formula can be directly used to compute $f^{-1}\,{mod}\,x^{l}$ without any additional cost, when $l$ is not a power of 2.

cs.SC↗

arXiv2011

Adleman-Manders-Miller Root Extraction Method Revisited

In 1977, Adleman, Manders and Miller had briefly described how to extend their square root extraction method to the general $r$th root extraction over finite fields, but not shown enough details. Actually, there is a dramatic difference between the square root extraction and the general $r$th root extraction because one has to solve discrete logarithms for $r$th root extraction. In this paper, we clarify their method and analyze its complexity. Our heuristic presentation is helpful to grasp the method entirely and deeply.

cs.SC↗

arXiv2011

A Heuristic Description of Fast Fourier Transform

Fast Fourier Transform (FFT) is an efficient algorithm to compute the Discrete Fourier Transform (DFT) and its inverse. In this paper, we pay special attention to the description of complex-data FFT. We analyze two common descriptions of FFT and propose a new presentation. Our heuristic description is helpful for students and programmers to grasp the algorithm entirely and deeply.

math.NA↗

arXiv2011

Improvement Of Barreto-Voloch Algorithm For Computing $r$th Roots Over Finite Fields

Root extraction is a classical problem in computers algebra. It plays an essential role in cryptosystems based on elliptic curves. In 2006, Barreto and Voloch proposed an algorithm to compute $r$th roots in ${F}_{q^m} $ for certain choices of $m$ and $q$. If $r\,||\,q-1$ and $ (m, r)=1, $ they proved that the complexity of their method is $\widetilde{\mathcal {O}}(r(\log m+\log\log q)m\log q) $. In this paper, we extend the Barreto-Voloch algorithm to the general case that $r\,||\,q^m-1$, without the restrictions $r\,||\,q-1$ and $(m, r)=1 $. We also specify the conditions that the Barreto-Voloch algorithm can be preferably applied.

cs.SC↗