## angela210793 3 years ago May someone help me pls???

1. angela210793

You have matrices A(mxn) and B(nxp) how many operations of multiplication and addition are needed to calculate AxB???

2. amistre64

AxB i take means matrix multiplication; otherwise knnown as a dot product

3. angela210793

yes tht's wht it means

4. amistre64

there is some 2^something jargon that i can never recall but we could try to work it out

5. amistre64

mxn * nxp every m rows is doted to every n column; and each term is added n-1 times

6. amistre64

1 2 3 a b c a1 + b2 + b3 = 3 multiplicataion and 2 addition for a total of 5 flops i think the term is 1x3 * 3x1 = 5 flops 123 ad 456 be cf a1+b2+c3 a4+b5+c6 def def 12 multiples and 8 adds makes 20 for a 2x3*3x2 this might take awhile lol

7. amistre64

n*m sets of dots each dot has n multipliers in it n*m*n and each has n-1 adds in it n*n*m*(n-1) maybe

8. amistre64

mxn nxp m*p dot products each one having n multipliers and n-1 additions might sound better to me without resorting to google lol

9. amistre64

2x3 3x2 (2*2)(3*2) = 24 n+n-1 operations per row ....

10. amistre64

(2*2)(3+2) = 20 that seemst o work

11. angela210793

|dw:1329485736294:dw| don't u have n*n in there???

12. amistre64

mxn * nxp (m*p)(n+n-1)

13. amistre64

so a 2x2 * 2x1 2*1(2+1) = 6 operations ab 1 cd 2 a1+b2 c1+d2 2*3 = 6 operations 3x2 * 2x2 should equal 6(3), 18 flops? ab 12 cd 34 ef a1,b3 c1,d3 e1,fe and 9 more = 18

14. amistre64

m*p(n+n-1) is good to me

15. amistre64

this notebook rental is sooo small, hard to see the screen :/

16. amistre64

the n parts do have n multiplications, but there is n-1 additions between them

17. angela210793

After reading it 100 times i finally understood it :) Thank u very much ^^

18. amistre64

youre welcome :)