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An Application to Software Design

The Chinese Remainder Theorem is a result from elementary number theory about the solution of systems of simultaneous congruences. The Chinese mathematician Sun-tsï wrote about the theorem in the first century A.D. This theorem has some interesting consequences in the design of software for parallel processors.

Lemma

Let \(m\) and \(n\) be positive integers such that \(\gcd( m, n) = 1\). Then for \(a, b \in {\mathbb Z}\) the system \[\begin{aligned}x & \equiv a \pmod{m} \\ x & \equiv b \pmod{n}\end{aligned}\] has a solution. If \(x_1\) and \(x_2\) are two solutions of the system, then \(x_1 \equiv x_2 \pmod{mn}\).

Proof

The equation \(x \equiv a \pmod{m}\) has a solution since \(a + km\) satisfies the equation for all \(k \in {\mathbb Z}\). We must show that there exists an integer \(k_1\) such that \[\begin{aligned}\end{aligned}\]. This is equivalent to showing that \[\begin{aligned}\end{aligned}\] has a solution for \(k_1\). Since \(m\) and \(n\) are relatively prime, there exist integers \(s\) and \(t\) such that \(ms + nt = 1\). Consequently, \[\begin{aligned}\end{aligned}\], or \[\begin{aligned}\end{aligned}\]. Now let \(k_1 = (b-a)s\).

To show that any two solutions are congruent modulo \(mn\), let \(c_1\) and \(c_2\) be two solutions of the system. That is, \[\begin{aligned}c_i & \equiv a \pmod{m} \\ c_i & \equiv b \pmod{n}\end{aligned}\] for \(i = 1, 2\). Then \[\begin{aligned}c_2 & \equiv c_1 \pmod{m} \\ c_2 & \equiv c_1 \pmod{n}\end{aligned}\]. Therefore, both \(m\) and \(n\) divide \(c_1 - c_2\). Consequently, \(c_2 \equiv c_1 \pmod{mn}\).

Example

Let us solve the system \[\begin{aligned}x & \equiv 3 \pmod{4} \\ x & \equiv 4 \pmod{5}\end{aligned}\]. Using the Euclidean algorithm, we can find integers \(s\) and \(t\) such that \(4s + 5t = 1\). Two such integers are \(s = 4\) and \(t = -3\). Consequently, \[\begin{aligned}\end{aligned}\].

Special software is required for calculations involving larger integers which cannot be added directly by the machine. By using the Chinese Remainder Theorem we can break down large integer additions and multiplications into calculations that the computer can handle directly. This is especially useful on parallel processing computers which have the ability to run several programs concurrently.

Condensed: the full section is in Judson, Abstract Algebra: Theory and Applications.

Manje Akukho kalkuli yokuxazulula le nto, kodwa amaphuzu ayo anga kalkuli. Zama enye ngezansi, noma ubhale yakho.

Qhubeka usebenza

I-akhawunti emahhala ifaka iziphawulo kulesifundo ngasinye, irekhodi lokuthi yini oqedile, izinkinga zakho ezixazululiwe endaweni eyodwa, nodokotela owaziyo ongabuza mayelana nalekhasi. I-matematics ivulekile kubo bonke, noma ngabe babhalise noma cha.

Bhala Ngena

Amaphawu asetshenziswa lapha

Chofoza noma yiluphi uphawu lwesibonakaliso ukuze uthole ukuchaza okuphelele, isithombe, kanye nokuthi iyiphi inhlamvu ekhona ekhuluma ngaso.

Imibuzo abantu bebuza

What is a group, in plain words?

A set with one operation that is associative, has an identity, and lets every element be undone. Symmetries of any object form a group. That is where the idea came from.

What is the difference between a ring and a field?

A ring has addition and multiplication that behave like the integers (you cannot always divide); a field is a ring where every non-zero element has a reciprocal, like the rationals or the reals.

Amangxenye wale khasi aguqulwe kusuka Judson, Abstract Algebra: Theory and Applications (GFDL 1.3). I-condensed futhi iphinde icaciswe lapha; amaphutha awusizo.

Okuningi Abstract Algebra

Groups Subgroups, cosets and Lagrange's theorem Cyclic groups and permutation groups Homomorphisms, normal subgroups and quotient groups Rings and fields Galois theory: why the quintic has no formula