Okay, then, implementing a full matrix_power() with PDL using "same algorithm as python numpy" (https://docs.scipy.org/doc/numpy-1.12.0/reference/generated/numpy.linalg.matrix_power.html), which says "the power is computed by repeated matrix squarings and matrix multiplications" -- which is then the matrix version of https://en.wikipedia.org/wiki/Exponentiation_by_squaring.

#!/usr/bin/perl
# [id://1229234]
use warnings;
use strict;
use PDL;

sub matrix_power {
    my ($M,$n) = @_;
    if($n<0) {
        return matrix_power(1/$M, -$n);
    } elsif ($n==0) {
        return 1;
    } elsif ($n==1) {
        return $M;
    } elsif (0 == $n % 2) {
        return matrix_power($M x $M, $n/2);
    } else {
        return $M x matrix_power($M x $M, ($n-1)/2);
    }
}

my $x = pdl([0,1], [2,3]);
for(0 .. 3) {
    print "M ** $_ = " . matrix_power( $x, $_ ) . "\n";
}

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In reply to Re^4: In PDL, how to raise a matrix $m to a power $v by pryrt
in thread In PDL, how to raise a matrix $m to a power $v by Anonymous Monk

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