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tensor: scalar as rank==0 special case

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Jiri Pittner
2025-11-06 15:45:12 +01:00
parent b3c7d21268
commit b24cd24747
3 changed files with 48 additions and 11 deletions
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37
t.cc
View File

@@ -3362,7 +3362,7 @@ for(int i=0; i<n; ++i)
if(1)
if(0)
{
int n=5;
INDEXGROUP ag;
@@ -3959,6 +3959,41 @@ for(int k=0; k<n; ++k)
cout<<t2;
}
if(0)
{
//scalar as trivial tensor rank 0 case
Tensor<double> t(2.),u(3.);
cout <<t<<endl;
SUPERINDEX I;
FLATINDEX J;
cout <<t(I)<<endl;
cout <<u(J)<<endl;
cout <<t+u<<endl;
cout <<t*u<<endl;
cout <<t.dot(u)<<endl;
}
if(1)
{
int r,n;
cin>>r>>n;
INDEXGROUP shape;
{
shape.number=r;
//shape.symmetry= 0;
shape.symmetry= -1;
shape.range=n;
shape.offset=0;
}
Tensor<double> x(shape);
x.randomize(1.);
cout<<x;
Tensor<double> xf=x.flatten();
cout <<xf;
cout <<x.dot(x) <<" "<< xf.dot(xf)<<endl;
}
}//main

18
tensor.cc
View File

@@ -34,7 +34,7 @@ int r=0;
for(int i=0; i<shape.size(); ++i)
{
const indexgroup *sh = &(* const_cast<const NRVec<indexgroup> *>(&shape))[i];
if(sh->number<=0) laerror("empty index group"); //we do not support scalar as a trivial case
if(sh->number<=0) laerror("empty index group"); //scalar must have shape.size()==0, not empty index group
r+=sh->number;
}
myrank=r;
@@ -46,7 +46,7 @@ return r;
template<typename T>
LA_largeindex Tensor<T>::calcsize()
{
if(shape.size()==0) laerror("tensor must have rank at least 1");
if(shape.size()==0) return 1; //scalar
groupsizes.resize(shape.size());
cumsizes.resize(shape.size());
LA_largeindex s=1;
@@ -578,6 +578,7 @@ std::ostream & operator<<(std::ostream &s, const Tensor<T> &x)
{
s<<x.shape;
s<<x.names;
if(x.rank()==0) {s<<x.data[0]; return s;}
sout= &s;
x.constloopover(&outputcallback<T>);
return s;
@@ -1383,25 +1384,26 @@ loopover(permutationalgebra_callback2);
template<typename T>
void Tensor<T>::split_index_group(int group)
{
const indexgroup *sh = &(* const_cast<const NRVec<indexgroup> *>(&shape))[0];
if(group<0||group >= shape.size()) laerror("illegal index group number");
if(shape[group].number==1) return; //nothing to split
if(shape[group].symmetry!=0) laerror("only non-symmetric index group can be splitted, use flatten instead");
if(sh[group].number==1) return; //nothing to split
if(sh[group].symmetry!=0) laerror("only non-symmetric index group can be splitted, use flatten instead");
NRVec<indexgroup> newshape(shape.size()+shape[group].number-1);
NRVec<indexgroup> newshape(shape.size()+sh[group].number-1);
int gg=0;
for(int g=0; g<shape.size(); ++g)
{
if(g==group)
{
for(int i=0; i<shape[group].number; ++i)
for(int i=0; i<sh[group].number; ++i)
{
newshape[gg] = shape[group];
newshape[gg] = sh[group];
newshape[gg].number = 1;
gg++;
}
}
else
newshape[gg++] = shape[g];
newshape[gg++] = sh[g];
}
shape=newshape;

4
tensor.h
View File

@@ -40,7 +40,6 @@
#include "miscfunc.h"
//TODO:
//@@@@@@how to handle contractions yielding a scalar - special treatment, support special case of rank=0 tensor?
//@@@contraction inside one tensor - compute resulting shape, loopover the shape, create index into the original tensor + loop over the contr. index, do the summation, store result
//@@@ will need to store vector of INDEX to the original tensor for the result's flatindex
//@@@ will not be particularly efficient
@@ -187,7 +186,8 @@ public:
SUPERINDEX inverse_index(LA_largeindex s) const; //inefficient, but possible if needed
//constructors
Tensor() : myrank(0) {};
Tensor() : myrank(-1) {};
explicit Tensor(const T &x) : myrank(0), data(1) {data[0]=x;}; //scalar
Tensor(const NRVec<indexgroup> &s) : shape(s) { data.resize(calcsize()); calcrank();}; //general tensor
Tensor(const NRVec<indexgroup> &s, const NRVec<INDEXNAME> &newnames) : shape(s), names(newnames) { data.resize(calcsize()); calcrank(); if(names.size()!=myrank && names.size()!=0) laerror("bad number of index names");}; //general tensor
Tensor(const NRVec<indexgroup> &s, const NRVec<T> &mydata) : shape(s) { LA_largeindex dsize=calcsize(); calcrank(); if(mydata.size()!=dsize) laerror("inconsistent data size with shape"); data=mydata;}