2004-05-28, 16:26 | #1 |
May 2004
31_{8} Posts |
Fast way to square???
can any one help me to find out wheather it multiples faster to get the "square of a number i.e x^2 "or not. if you have better solution , could u please give me.
y(1) = 1; y(n) = y(n-1) + ( 1 + 2* (n-1)), n > 1 eg: to find 4^2 y(1) = 1 y(2) = y(1) + (1 + 2*(1)) => 4 y(3) = y(2) + (1 + 2*(2)) => 9 y(4) = y(3) + (1 + 2*(3)) => 16 A CPP Program.... Code:
void test2() { long long max = 60000; long long y = 1; time_t t1, t2; time(&t1); for (long long j = 0; j < max / 3; j++) for (long long i = 1; i <= max; i++) { y = i * i; } time(&t2); cout<<"muls:\n\t"<<"t1:" << t1 << "\n\tt2:" <<t2 <<"\n"<<(t2-t1)<<endl; time(&t1); for (long long j = 0; j < max / 3; j++) for (long long i = 2; i <= max; i++) { y = y + (1 + (i << 1)); } time(&t2); cout<<"muls:\n\t"<<"t1:" << t1 << "\n\tt2:" <<t2 <<"\n"<<(t2-t1)<<endl; } Code:
muls: t1:1080490498 t2:1080490523 25 s muls: t1:1080490523 t2:1080490537 14 s Code:
private static void test1() { long max = 60000; long y = 1; long t1, t2; t1 = System.currentTimeMillis(); for (int j = 0; j < max / 3; j++) for (int i = 1; i <= max; i++) { y = i * i; } t2 = System.currentTimeMillis(); System.out.println("muls:" + (t2 - t1)); t1 = System.currentTimeMillis(); for (int j = 0; j < max / 3; j++) for (int i = 2; i <= max; i++) { y = y + (1 + (i << 1)); } t2 = System.currentTimeMillis(); System.out.println("mul:" + (t2 - t1)); } Code:
muls:10031 ms mul:5906 ms |
2004-05-28, 16:58 | #2 |
May 2004
2^{4}·5 Posts |
The algorithm you've given is probably close to optimal for computing the square of all integers 1 <= x <= max.
However, if you only want the square of only one number then straightforward multiplication is much quicker. For the range 1 <= x <= 60000, there is no quicker way to square a number than just "y = x * x;" For larger numbers whose squares don't fit in a word, there are more efficient algorithms. A description of many of them is given on Carey Bloodworth's page |
2004-05-29, 01:54 | #3 |
May 2004
5^{2} Posts |
thanks friend...what u say is right...
does any thing could be done faster using the binary techniques |
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