if (x.length() != (originalString.length() * count)) {
        throw new RuntimeException("Wrong length: " + x);
      }
    }
  }

  private static String oldRepeat(String string, int count) {
    // If this multiplication overflows, a NegativeArraySizeException or
    // OutOfMemoryError is not far behind
    final int len = string.length();
    final int size = len * count;
    char[] array = new char[size];

      if (x.length() != (originalString.length() * count)) {
        throw new RuntimeException("Wrong length: " + x);
      }
    }
  }

  private static String oldRepeat(String string, int count) {
    // If this multiplication overflows, a NegativeArraySizeException or
    // OutOfMemoryError is not far behind
    final int len = string.length();
    final int size = len * count;
    char[] array = new char[size];

}

var basepointTablePrecomp struct {
	table    [32]affineLookupTable
	initOnce sync.Once
}

// ScalarBaseMult sets v = x * B, where B is the canonical generator, and
// returns v.
//
// The scalar multiplication is done in constant time.
func (v *Point) ScalarBaseMult(x *Scalar) *Point {
	basepointTable := basepointTable()

	// Write x = sum(x_i * 16^i) so  x*B = sum( B*x_i*16^i )
	// as described in the Ed25519 paper
	//

	// division by base**(-fcount), which equals a multiplication by
	// base**fcount. An exponent means multiplication by ebase**exp.
	// Multiplications are commutative, so we can apply them in any
	// order. We only have powers of 2 and 10, and we split powers
	// of 10 into the product of the same powers of 2 and 5. This
	// may reduce the size of shift/multiplication factors or

		hash ^= sum64a(c)
		hash *= prime64
	}
	*s = hash
	return len(data), nil
}

func (s *sum128) Write(data []byte) (int, error) {
	for _, c := range data {
		// Compute the multiplication
		s0, s1 := bits.Mul64(prime128Lower, s[1])
		s0 += s[1]<<prime128Shift + prime128Lower*s[0]
		// Update the values
		s[1] = s1
		s[0] = s0
		s[1] ^= uint64(c)
	}
	return len(data), nil
}

which can be handled without a recursive call. That is, the algorithm uses two
full iterations, each using an n-by-n/2-digit division and an n/2-by-n/2-digit
multiplication, along with a few n-digit additions and subtractions. The standard
n-by-n-digit multiplication algorithm requires O(n²) time, making the overall
algorithm require time T(n) where

	T(n) = 2T(n/2) + O(n) + O(n²)

//
// To interact with the nistec package, points are encoded into and decoded from
// properly formatted byte slices. All big.Int use is limited to this package.
// Encoding and decoding is 1/1000th of the runtime of a scalar multiplication,
// so the overhead is acceptable.
type nistCurve[Point nistPoint[Point]] struct {
	newPoint func() Point
	params   *CurveParams
}

// nistPoint is a generic constraint for the nistec Point types.

func karatsuba(z, x, y nat) {
	n := len(y)

	// Switch to basic multiplication if numbers are odd or small.
	// (n is always even if karatsubaThreshold is even, but be
	// conservative)
	if n&1 != 0 || n < karatsubaThreshold || n < 2 {
		basicMul(z, x, y)
		return
	}
	// n&1 == 0 && n >= karatsubaThreshold && n >= 2

	// Karatsuba multiplication is based on the observation that
	// for two numbers x and y with:
	//

    (TF_MulOp:$dest1 $arg0, (TF_RsqrtOp:$dest2 $arg1)),
  [], [(CopyAttrs $src, $dest1), (CopyAttrs $src, $dest2)]>;

// Replace division by a constant with a multiplication by a reciprocal of that
// constant. Floating point division can be ~10x more expensive than a
// multiplication.
def RealDivWithConstDivisor : Pat<
  (TF_RealDivOp:$src $arg0, (TF_ConstOp FloatElementsAttr<32>:$value)),

package ssa

import (
	"math/big"
	"math/bits"
)

// So you want to compute x / c for some constant c?
// Machine division instructions are slow, so we try to
// compute this division with a multiplication + a few
// other cheap instructions instead.
// (We assume here that c != 0, +/- 1, or +/- 2^i.  Those
// cases are easy to handle in different ways).

// Technique from https://gmplib.org/~tege/divcnst-pldi94.pdf