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Java svm uses faster Math.pow instead of powi #109

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Java svm uses faster Math.pow instead of powi #109

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16 changes: 2 additions & 14 deletions java/libsvm/svm.java
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Original file line number Diff line number Diff line change
Expand Up @@ -152,26 +152,14 @@ void swap_index(int i, int j)
if(x_square != null) do {double tmp=x_square[i]; x_square[i]=x_square[j]; x_square[j]=tmp;} while(false);
}

private static double powi(double base, int times)
{
double tmp = base, ret = 1.0;

for(int t=times; t>0; t/=2)
{
if(t%2==1) ret*=tmp;
tmp = tmp * tmp;
}
return ret;
}

double kernel_function(int i, int j)
{
switch(kernel_type)
{
case svm_parameter.LINEAR:
return dot(x[i],x[j]);
case svm_parameter.POLY:
return powi(gamma*dot(x[i],x[j])+coef0,degree);
return Math.pow(gamma*dot(x[i],x[j])+coef0,degree);
case svm_parameter.RBF:
return Math.exp(-gamma*(x_square[i]+x_square[j]-2*dot(x[i],x[j])));
case svm_parameter.SIGMOID:
Expand Down Expand Up @@ -231,7 +219,7 @@ static double k_function(svm_node[] x, svm_node[] y,
case svm_parameter.LINEAR:
return dot(x,y);
case svm_parameter.POLY:
return powi(param.gamma*dot(x,y)+param.coef0,param.degree);
return Math.pow(param.gamma*dot(x,y)+param.coef0,param.degree);
case svm_parameter.RBF:
{
double sum = 0;
Expand Down
16 changes: 2 additions & 14 deletions java/libsvm/svm.m4
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Original file line number Diff line number Diff line change
Expand Up @@ -152,26 +152,14 @@ abstract class Kernel extends QMatrix {
if(x_square != null) swap(double,x_square[i],x_square[j]);
}

private static double powi(double base, int times)
{
double tmp = base, ret = 1.0;

for(int t=times; t>0; t/=2)
{
if(t%2==1) ret*=tmp;
tmp = tmp * tmp;
}
return ret;
}

double kernel_function(int i, int j)
{
switch(kernel_type)
{
case svm_parameter.LINEAR:
return dot(x[i],x[j]);
case svm_parameter.POLY:
return powi(gamma*dot(x[i],x[j])+coef0,degree);
return Math.pow(gamma*dot(x[i],x[j])+coef0,degree);
case svm_parameter.RBF:
return Math.exp(-gamma*(x_square[i]+x_square[j]-2*dot(x[i],x[j])));
case svm_parameter.SIGMOID:
Expand Down Expand Up @@ -231,7 +219,7 @@ abstract class Kernel extends QMatrix {
case svm_parameter.LINEAR:
return dot(x,y);
case svm_parameter.POLY:
return powi(param.gamma*dot(x,y)+param.coef0,param.degree);
return Math.pow(param.gamma*dot(x,y)+param.coef0,param.degree);
case svm_parameter.RBF:
{
double sum = 0;
Expand Down