you can either use matrix multiplication (see resultmatrix2) or tensordot (see resultmatrix3). on my computer I have: 1. 15.6 sec with your code 2. 0.072 sec with resultmatrix2 3. 0.040 sec with tensordot (resultmatrix3) (-- which is a 400x speed) -------------------------------------------- from numpy import * items=25 sample=5 totalcols=8100 #matrixone=matrix(zeros((items,totalcols))) #matrixtwo=matrix(zeros((items,totalcols))) matrixone=matrix(random.rand(items, totalcols)) matrixtwo=matrix(random.rand(items, totalcols)) resultmatrix=matrix(zeros((items,sample))) resultmatrix2=matrix(zeros((items,sample))) resultmatrix3=matrix(zeros((items,sample))) # your code for i in range(items): for j in range(sample): tval=0.0 for p in range(totalcols): tval +=matrixone[ j , p ] * matrixtwo[ i , p ] resultmatrix[ i, j ]=abs(tval) # matrix multiplication for i in range(items): for j in range(sample): resultmatrix2[ i, j ] = abs(matrixone[j,:] * matrixtwo[i,:].T) # tensordot resulmatrix3 = tensordot(matrixone[:sample,:], matrixtwo.T, axes=1).T --------------------------------------- hth, L. On Dec 25, 2007 5:16 PM, Louis Wicker <Louis.Wicker@noaa.gov> wrote:

Hi there - quick suggestion on Xmas morning - others are much more familar. You do not want to use a loop to do the matrix multiply, you want to use the intrinsic functions assoicated with matrix.

So you want something like

res = Math.abs( matmul(arrayone, arraytwo) )

note - that is not real code, just symbolic code. I am sure this is easily found in the documentation.

cheers!

Lou

On Dec 25, 2007, at 8:47 AM, devnew@gmail.c om <devnew@gmail.com> w le-interchange-newline">

hi i am doing some maths calculations involving matrices of double values using numpy.matrix ,

java code for this is something like

int items=25; int sample=5; int totalcols=8100; double[][]dblarrayone=new double[items][totalcols]; double[][]dblarraytwo=new double[items][totalcols]; //their elements are set elsewhere before calculation

double[][] resultarray = new double[items][sample];

for(int i=0;i<items;i++){ for(int j=0;j<sample;j++){ double tval=0.0; for(int p=0;p<totalcols;p++) tval+=dblarrayone[j][p] * dblarraytwo[i][p]; resultarray[i][j]=Math.abs(tval);

}

}

so I wanted to do the same in python ..(may b recommended way..) i am storing the filled matrices and other values as instance variable of a class and access them by self.whatever...

self.items=25 self.sample=5 self.totalcols=8100 #self.matrixone,self.matrixtwo are numply matix objects with already filled elements #but for testing i filled it with zeros self.matrixone=matrix(zeros((items,totalcols))) self.matrixtwo=matrix(zeros((items,totalcols))) resultmatrix=matrix(zeros((self.items,self.sample)))

for i in range(self.items): for j in range(self.sample): tval=0.0 for p in range(self.totalcols): tval +=self.matrixone[ j , p ] * self.matrixtwo[ i , p ] resultmatrix[ i, j ]=abs(tval)

here I found that while the java code takes ba br>execute the code ,the python code takes something like 53 secs to execute !!..I am baffled by this ..can anyone advise me how i can improve this? (i want to code in python so I can't use c,c++ , java)

dn _______________________________________________ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion

| Dr. Louis J. Wicker | NSSL/WRDD Rm 4366 | National Weather Center < "Apple-style-span" style="line-height: 16px;; font-size: 14px; "> | 120 David L. Boren Boulevard, Norman, OK 73072 | | E-mail: Louis.Wicker@noaa.gov | HTTP: www.nssl.noaa.gov/~lwicker <http://www.nssl.noaa.gov/%7Elwicker> | Phone: (405) 325-6340 | Fax: (405) 325-6780 | | "Programming is not just creating strings of instructions | for a computer to execute. It's also 'literary' in that you | are trying to communicate a program structure to | other humans reading the code." - Paul Rubin | |"Real efficiency comes from elegant solutions, not optimiz ed progr le="font-size: 14px; ">| Optimization is always just a few correctness-preserving transformations | away." - Jonathan Sobel

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