AI Engine API provides operations to change the location of the elements within a vector, to extract subvector from larger vector, or to combine the elements from two or more vectors.
The following APIs are provided to retrieve half of the vector by specific patterns.
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aie::filter_even - Returns a vector of half the size by: out = { v[0:step], v[2*step:3*step], ... }
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aie::filter_odd - Returns a vector of half the size by: out = { v[step:2*step], v[3*step:4*step], ... }
aie::vector<int32,8> result_e=aie::filter_even(xbuff, /*step=*/1);
aie::vector<int32,8> result_o=aie::filter_even(xbuff, /*step=*/4);The following figures show how elements are chosen by aie::filter_even and aie::filter_odd.
aie::select can be used to choose elements
from two vectors (or a scalar and a vector) to form a new vector. aie::mask is used for specifying the element to
choose.
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aie::select - Choose elements by each bit of mask value: out = {mask[0] == 0? a[0] : b[0], …}
aie::vector<int32,8> vc=aie::select(va,vb,msk_value);//vc[i]=(mask_value[i]==0)?va[i]:vb[i]AI Engine API provides following functions to shift vector elements by a specific number but maintain the vector size and element values.
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aie::shuffle_down - Shift elements down by n: out = {v[n], v[n+1], …, v[Elems-1], undefined[0],…,undefined[n-1]}. Higher elements of output(out[n],out[n+1],…) are undefined. "Elems" is the vector size.
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aie::shuffle_up - Shift elements up by n: out = {undefined[0],…,undefined[n-1],v[0], v[1], …}. Lower elements of output(out[0],…,out[n-1]) are undefined.
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aie::shuffle_down_rotate - Rotate elements down by n: out = {v[n], v[n+1], …,v[Elems-1], v[0], …,v[n-1]}.
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aie::shuffle_up_rotate - Rotate elements up by n: out = {v[Elems-n], …, v[Elems-1], v[0], …,v[n-1]}.
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aie::shuffle_down_fill - Shift elements down by n and fill with elements from a second vector: out = {v[n], v[n+1], …, v[Elems-1], fill[0],…,fill[n-1]}. Higher elements of output(out[n],out[n+1],…) are filled with elements from second vector "fill"(fill[0],…,fill[n-1]).
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aie::shuffle_up_fill - Shift elements up by n and fill with elements from a second vector: out = {fill[Elems-n],…,fill[Elems-1],v[0], v[1], …}. Lower elements of output(out[0],…,out[n-1]) are filled with elements from second vector "fill"(fill[Elems-n],…,fill[Elems-1]).
aie::vector<int32,8> v,fill;
//v_d[0:4]=v[3:7], (v_d[5],v_d[6],v_d[7] are undefined)
auto v_d=aie::shuffle_down(v,3);
//v_u[3:7]=v[0:4], (v_u[0],v_u[1],v_u[2] are undefined)
auto v_u=aie::shuffle_up(v,3);
auto vd_r=aie::shuffle_down_rotate(v,3);//vd_r[0:4]=v[3:7],vd_r[5:7]=v[0:2]
auto vu_r=aie::shuffle_up_rotate(v,3);//vu_r[3:7]=v[0:4],vu_r[0:2]=v[5:7]
//v_d_fill[0:4]=v[3:7], v_d_fill[5:7]=fill[0:2]
auto v_d_fill=aie::shuffle_down_fill(v,fill,3);
//v_u_fill[3:7]=v[0:4], v_u_fill[0:2]=fill[5:7]
auto v_u_fill=aie::shuffle_up_fill(v,fill,3);A vector can be reversed by:
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aie::reverse - Reverse elements by: out = {v[Elems-1], …, v[1], v[0]}
aie::vector<int32,8> v_rev=aie::reverse(v,3);//v_rev[0:7]=v[7:0]
AI Engine API provides functions
to shuffle two input vectors and combine them into the larger output vectors. The
two vectors must be the same type and size. The return type is std::pair.
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aie::interleave_zip - Select and combine two vectors by this pattern: out = { v1[0:step], v2[0:step], v1[step:2*step], v2[step:2*step], ... }
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aie::inerleave_unzip - Select and combine two vectors by this pattern: out = {
v1[0:step], v1[2*step:3*step], ..., v2[0:step], v2[2*step:3*step], ...,
v1[step:2*step], v1[3*step:4*step], ..., v2[step:2*step], v2[3*step:4*step],
... } Note: The parameter
stepmust be a power of two.
The following example takes two vectors with reals in rva and imaginary in rvb (with type aie::vector<int32,8>) and creates a new complex vector. It also
shows how to extract real and imaginary parts back and compare them with the
original values.
aie::vector<int32,8> rva,rvb;
auto rv=aie::interleave_zip(rva,rvb,/*step*/1);
aie::vector<cint32,8> cv=aie::concat(rv.first.cast_to<cint32>(),rv.second.cast_to<cint32>());
auto [uva,uvb]=aie::interleave_unzip(rv.first,rv.second,/*step*/1);
bool ret=aie::equal(rva,uva) && aie::equal(rvb,uvb);//return true