inner

inner($a, $b) – inner (dot) product along the first dimension.

Given two ndarrays with matching first-axis length n, computes c = sum_i a_i * b_i. For 1-D inputs this is the standard dot product, a 0-dimensional result; for higher-rank inputs the contraction is over axis 0 and the remaining axes broadcast.

Signature

$c = inner($a, $b);        # function form
$c = $a->inner($b);        # method form
inner($a, $b, $c);         # writes into $c, returns nothing

Bad values

If any element of $a or $b along the first dimension is bad, that result is bad.

Examples

use PDL;
my $a = pdl([1, 2, 3]);
my $b = pdl([4, 5, 6]);
print inner($a, $b);            # 32   (1*4 + 2*5 + 3*6)
print $a->inner($b);            # 32   (method form)

# Scalar-on-vector also works (scalar broadcasts to each element)
print inner(pdl([1, 2, 3]), 2); # 12   (1*2 + 2*2 + 3*2)

Errors

Croaks when the dimensions do not match, or with the usage when given fewer than two or more than three arguments.