user: 请将这段汇编代码片段转换成等效的C代码：

```asm
<Gauss_siedel>:
  endbr64
  push   %r15
  lea    0x958(%rsi),%rax
  push   %r14
  push   %r13
  push   %r12
  mov    %rdx,%r12
  push   %rbp
  mov    %rcx,%rbp
  push   %rbx
  xor    %ebx,%ebx
  sub    $0x38,%rsp
  mov    %rax,0x18(%rsp)
  lea    0x960(%rdi),%rax
  mov    %rdi,0x8(%rsp)
  mov    %rsi,0x10(%rsp)
  mov    %rax,0x20(%rsp)
L28:
  xor    %eax,%eax
  mov    %r12,%r14
  xor    %r13d,%r13d
  call   <boundary_pressure@plt>
  mov    0x18(%rsp),%r11
  mov    0x20(%rsp),%r15
  mov    %r12,%r9
  movq   D27(%rip),%xmm2
  mov    $0x12c,%r10d
  mov    %r11,%rdi
  mov    %r15,%r8
  movapd %xmm2,%xmm3
L33:
  lea    -0x12a(%r10),%rdx
  lea    0x0(%rbp,%r13,8),%rsi
  mov    %r15,%rax
  mov    %r14,%rcx
L22:
  test   $0x1,%dl
  jne    L15
  movsd  (%rcx),%xmm0
  movsd  0x8(%rcx),%xmm1
  mulsd  (%rax),%xmm0
  mulsd  0x10(%rax),%xmm1
  addsd  %xmm1,%xmm0
  movsd  (%rsi),%xmm1
  mulsd  -0x958(%rax),%xmm1
  addsd  %xmm1,%xmm0
  movsd  0x950(%rsi),%xmm1
  mulsd  0x968(%rax),%xmm1
  addsd  %xmm1,%xmm0
  movsd  (%r11,%rdx,8),%xmm1
  subsd  %xmm0,%xmm1
  movsd  %xmm1,0x8(%rax)
  movsd  0x8(%rcx),%xmm0
  addsd  (%rcx),%xmm0
  xorpd  %xmm2,%xmm1
  addsd  0x950(%rsi),%xmm0
  addsd  (%rsi),%xmm0
  divsd  %xmm0,%xmm1
  movsd  %xmm1,0x8(%rax)
L15:
  add    $0x1,%rdx
  add    $0x8,%rcx
  add    $0x8,%rax
  add    $0x8,%rsi
  cmp    %rdx,%r10
  jne    L22
  add    $0x12a,%r13
  add    $0x1,%r10
  add    $0x958,%r11
  add    $0x958,%r14
  add    $0x960,%r15
  cmp    $0x15ae4,%r13
  jne    L33
  xor    %r11d,%r11d
  mov    $0x12c,%r10d
L0:
  lea    -0x12a(%r10),%rdx
  lea    0x0(%rbp,%r11,8),%rsi
  mov    %r8,%rax
  mov    %r9,%rcx
  nopl   0x0(%rax)
L12:
  test   $0x1,%dl
  je     L48
  movsd  (%rcx),%xmm0
  movsd  0x8(%rcx),%xmm1
  mulsd  (%rax),%xmm0
  mulsd  0x10(%rax),%xmm1
  addsd  %xmm1,%xmm0
  movsd  (%rsi),%xmm1
  mulsd  -0x958(%rax),%xmm1
  addsd  %xmm1,%xmm0
  movsd  0x950(%rsi),%xmm1
  mulsd  0x968(%rax),%xmm1
  addsd  %xmm1,%xmm0
  movsd  (%rdi,%rdx,8),%xmm1
  subsd  %xmm0,%xmm1
  movsd  %xmm1,0x8(%rax)
  movsd  (%rcx),%xmm0
  addsd  0x8(%rcx),%xmm0
  xorpd  %xmm3,%xmm1
  addsd  (%rsi),%xmm0
  addsd  0x950(%rsi),%xmm0
  divsd  %xmm0,%xmm1
  movsd  %xmm1,0x8(%rax)
L48:
  add    $0x1,%rdx
  add    $0x8,%rcx
  add    $0x8,%rax
  add    $0x8,%rsi
  cmp    %rdx,%r10
  jne    L12
  add    $0x12a,%r11
  add    $0x1,%r10
  add    $0x958,%rdi
  add    $0x958,%r9
  add    $0x960,%r8
  cmp    $0x15ae4,%r11
  jne    L0
  mov    0x10(%rsp),%rcx
  mov    0x8(%rsp),%rdx
  add    $0x1,%ebx
  mov    %rbp,%rsi
  mov    %r12,%rdi
  call   <compute_error@plt>
  mov    %ebx,%esi
  lea    D9(%rip),%rdi
  movsd  %xmm0,0x28(%rsp)
  call   <printf@plt>
  movsd  0x28(%rsp),%xmm0
  movsd  D14(%rip),%xmm4
  andpd  D31(%rip),%xmm0
  comisd %xmm0,%xmm4
  jbe    L28
  add    $0x38,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
```

tool_calls: name: unpack_data
arguments: data_label: D27
data_type: byte[8]
name: unpack_data
arguments: data_label: D9
data_type: string
name: unpack_data
arguments: data_label: D14
data_type: byte[8]
name: unpack_data
arguments: data_label: D31
data_type: qword[2]

tool: {"D27": [0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x80]}

tool: D9: iter=%d	error=%lf


tool: {"D14": [0x8d,0xed,0xb5,0xa0,0xf7,0xc6,0xb0,0x3e]}

tool: {"D31": [0x7fffffffffffffff,0x0000000000000000]}

assistant: ```c
void Gauss_siedel(double *P, double *fn, double *a_x, double *a_y) {
  long i, j, indx, indx_rght, indx_frnt, indx_lft, indx_bck, indx_ax, indx_ay;
  double P_old;
  double error;
  double tol = 1.0e-6;
  int iter = 0;
  for (;;) {
    boundary_pressure();
    for (i = 1; i < 300 - 1; i++) {
      for (j = 1; j < 300 - 1; j++) {
        indx = i * 300 + j;
        indx_rght = indx + 1;
        indx_frnt = indx + 300;
        indx_lft = indx - 1;
        indx_bck = indx - 300;
        indx_ax = (i - 1) * (300 - 1) + (j - 1);
        indx_ay = (i - 1) * (300 - 2) + (j - 1);
        if (((i + j) % 2) == 0) {
          P[indx] = -1.0 * (a_x[indx_ax] * P[indx_lft] + a_x[indx_ax + 1] * P[indx_rght] + a_y[indx_ay] * P[indx_bck] + a_y[indx_ay + (300 - 2)] * P[indx_frnt]) + 1.0 * 1.0 * fn[indx];
          P[indx] /= -1.0 * (a_x[indx_ax + 1] + a_x[indx_ax] + a_y[indx_ay + (300 - 2)] + a_y[indx_ay]);
        }
      }
    }
    for (i = 1; i < 300 - 1; i++) {
      for (j = 1; j < 300 - 1; j++) {
        indx = i * 300 + j;
        indx_rght = indx + 1;
        indx_frnt = indx + 300;
        indx_lft = indx - 1;
        indx_bck = indx - 300;
        indx_ax = (i - 1) * (300 - 1) + (j - 1);
        indx_ay = (i - 1) * (300 - 2) + (j - 1);
        if (((i + j) % 2) != 0) {
          P[indx] = -1.0 * (a_x[indx_ax] * P[indx_lft] + a_x[indx_ax + 1] * P[indx_rght] + a_y[indx_ay] * P[indx_bck] + a_y[indx_ay + (300 - 2)] * P[indx_frnt]) + 1.0 * 1.0 * fn[indx];
          P[indx] /= -1.0 * (a_x[indx_ax] + a_x[indx_ax + 1] + a_y[indx_ay] + a_y[indx_ay + (300 - 2)]);
        }
      }
    }
    iter++;
    error = compute_error(a_x, a_y, P, fn);
    printf("iter=%d\terror=%lf\n", iter, error);
    if (fabs(error) < tol) {
      break;
    }
  }
}
```