need help from someone who is familiar with the Scrypt algorithm

[joys]

Below is the scryptROMix part of the CL code of the Scrypt algorithm.
My question is WHY is the value 1024 fixed?
Shouldn't it be repeated as many times as SCRYPT_N??
plz help me..


DECLSPEC void scrypt_smix_loop (PRIVATE_AS uint4 *X, GLOBAL_AS uint4 *V0, GLOBAL_AS uint4 *V1, GLOBAL_AS uint4 *V2, GLOBAL_AS uint4 *V3, const u64 gid)
{
  const u32 ySIZE = SCRYPT_N / SCRYPT_TMTO;
  const u32 zSIZE = STATE_CNT4;

  const u32 x = (u32) gid;

  const u32 xd4 = x / 4;
  const u32 xm4 = x & 3;

  GLOBAL_AS uint4 *V;

  switch (xm4)
  {
    case 0: V = V0; break;
    case 1: V = V1; break;
    case 2: V = V2; break;
    case 3: V = V3; break;
  }

  // note: fixed 1024 iterations = forced -u 1024

  for (u32 N_pos = 0; N_pos < 1024; N_pos++)
  {
    const u32 k = X[zSIZE - 4].x & (SCRYPT_N - 1);

    const u32 y = k / SCRYPT_TMTO;

    const u32 km = k - (y * SCRYPT_TMTO);

    uint4 T[STATE_CNT4];

    for (u32 z = 0; z < zSIZE; z++) T[z] = V[CO];

    for (u32 i = 0; i < km; i++) salsa_r (T);

    for (u32 z = 0; z < zSIZE; z++) X[z] ^= T[z];

    salsa_r (X);
  }
}