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Fixed arange decomp for float dtype #123445

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Commits on Apr 5, 2024

  1. Fixed arange decomp for float dtype

    Description:
    
    Arange graph and C++ generated code are not optimal when arange is created directly using float32 dtype:
    ```python
    import torch
    
    def func(x):
        s = x.shape[-1]
        a = torch.arange(s, dtype=torch.float32)
        return s + a
    
    c_func = torch.compile(func)
    out = c_func(torch.rand(10))
    ```
    
    Graph on `main`:
    ```
     ===== Forward graph 0 =====
     /pytorch/torch/fx/_lazy_graph_module.py class <lambda>(torch.nn.Module):
        def forward(self):
            # File: check_arange_decomp.py:8 in func, code: a = torch.arange(s, dtype=torch.float32)
            iota: "i64[10]" = torch.ops.prims.iota.default(10, start = 0, step = 1, dtype = torch.int64, device = device(type='cpu'), requires_grad = False)
            convert_element_type: "f64[10]" = torch.ops.prims.convert_element_type.default(iota, torch.float64);  iota = None
            mul: "f64[10]" = torch.ops.aten.mul.Tensor(convert_element_type, 1);  convert_element_type = None
            add: "f64[10]" = torch.ops.aten.add.Tensor(mul, 0);  mul = None
            convert_element_type_1: "f32[10]" = torch.ops.prims.convert_element_type.default(add, torch.float32);  add = None
    
            # File: check_arange_decomp.py:9 in func, code: return s + a
            add_1: "f32[10]" = torch.ops.aten.add.Tensor(convert_element_type_1, 10);  convert_element_type_1 = None
            return (add_1,)
    ```
    and C++
    ```c++
    extern "C" void kernel(float* out_ptr0)
    {
        {
            #pragma GCC ivdep
            for(long x0=static_cast<long>(0L); x0<static_cast<long>(10L); x0+=static_cast<long>(1L))
            {
                auto tmp0 = c10::convert<long>(x0);
                auto tmp1 = c10::convert<double>(tmp0);   // <---- useless ops
                auto tmp2 = static_cast<double>(1.0);     // <----
                auto tmp3 = decltype(tmp1)(tmp1 * tmp2);  // <----
                auto tmp4 = static_cast<double>(0.0);     // <----
                auto tmp5 = decltype(tmp3)(tmp3 + tmp4);  // <----
                auto tmp6 = c10::convert<float>(tmp5);
                auto tmp7 = static_cast<float>(10.0);
                auto tmp8 = decltype(tmp6)(tmp6 + tmp7);
                out_ptr0[static_cast<long>(x0)] = tmp8;
            }
        }
    }
    ```
    
    However, if we manually create arange on i64 and then put to float32, generated graph and C++ code are more natural and benefit of a speed-up.
    ```python
    import torch
    
    def func(x):
        s = x.shape[-1]
        a = torch.arange(s).to(dtype=torch.float32)
        return s + a
    
    c_func = torch.compile(func)
    out = c_func(torch.rand(10))
    ```
    
    Graph on `main`:
    ```
     ===== Forward graph 0 =====
     /pytorch/torch/fx/_lazy_graph_module.py class <lambda>(torch.nn.Module):
        def forward(self):
            # File: check_arange_decomp.py:14 in func, code: a = torch.arange(s).to(dtype=torch.float32)
            iota: "i64[10]" = torch.ops.prims.iota.default(10, start = 0, step = 1, dtype = torch.int64, device = device(type='cpu'), requires_grad = False)
            convert_element_type: "f32[10]" = torch.ops.prims.convert_element_type.default(iota, torch.float32);  iota = None
    
            # File: check_arange_decomp.py:15 in func, code: return s + a
            add: "f32[10]" = torch.ops.aten.add.Tensor(convert_element_type, 10);  convert_element_type = None
            return (add,)
    ```
    
    C++ on `main`
    ```c++
    extern "C" void kernel(float* out_ptr0)
    {
        {
            #pragma GCC ivdep
            for(long x0=static_cast<long>(0L); x0<static_cast<long>(10L); x0+=static_cast<long>(1L))
            {
                auto tmp0 = c10::convert<long>(x0);
                auto tmp1 = c10::convert<float>(tmp0);
                auto tmp2 = static_cast<float>(10.0);
                auto tmp3 = decltype(tmp1)(tmp1 + tmp2);
                out_ptr0[static_cast<long>(x0)] = tmp3;
            }
        }
    }
    ```
    
    For example, the speed-up seen on upsample_nearest2d on cpu:
    ```
    [----------------------------------------------------------------------------------------------------------------------------------------------- Interpolate, cpu ----------------------------------------------------------------------------------------------------------------------------------------------]
                                                                                                                                    |  Eager (2.3.0a0+gitb4324ed) PR  |  Compiled (2.3.0a0+gitb4324ed) PR  |  Compiled (2.3.0a0+git0d1e705) Nightly  |  speed-up PR vs Nightly  |  Eager (2.3.0a0+git0d1e705) Nightly
    1 threads: ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
          Input (1, 3, 500, 400), torch.uint8, torch.contiguous_format | mode: nearest, align_corners: None, osize: (256, 256)      |        287.988 (+-10.399)       |         200.034 (+-8.630)          |            285.143 (+-8.412)            |     1.425 (+-0.000)      |          287.991 (+-11.302)
          Input (1, 3, 500, 400), torch.uint8, torch.channels_last | mode: nearest, align_corners: None, osize: (256, 256)          |        697.206 (+-27.033)       |         171.650 (+-7.381)          |            193.280 (+-5.840)            |     1.126 (+-0.000)      |          701.642 (+-26.461)
          Input (1, 3, 500, 400), torch.float32, torch.contiguous_format | mode: nearest, align_corners: None, osize: (256, 256)    |        149.149 (+-6.045)        |         222.780 (+-6.852)          |            299.968 (+-12.354)           |     1.346 (+-0.000)      |          145.055 (+-7.232)
          Input (1, 3, 500, 400), torch.float32, torch.channels_last | mode: nearest, align_corners: None, osize: (256, 256)        |        596.741 (+-27.970)       |         205.923 (+-8.648)          |            233.912 (+-7.742)            |     1.136 (+-0.000)      |          598.000 (+-25.630)
          Input (4, 3, 500, 400), torch.uint8, torch.contiguous_format | mode: nearest, align_corners: None, osize: (256, 256)      |       1095.734 (+-51.658)       |         700.850 (+-24.852)         |           1044.255 (+-38.216)           |     1.490 (+-0.000)      |         1097.977 (+-35.521)
          Input (4, 3, 500, 400), torch.uint8, torch.channels_last | mode: nearest, align_corners: None, osize: (256, 256)          |       2741.813 (+-122.917)      |         583.073 (+-16.998)         |            665.029 (+-36.331)           |     1.141 (+-0.000)      |         2722.388 (+-116.263)
          Input (4, 3, 500, 400), torch.float32, torch.contiguous_format | mode: nearest, align_corners: None, osize: (256, 256)    |        578.183 (+-37.266)       |         833.295 (+-42.264)         |           1131.341 (+-54.710)           |     1.358 (+-0.000)      |          584.953 (+-45.549)
          Input (4, 3, 500, 400), torch.float32, torch.channels_last | mode: nearest, align_corners: None, osize: (256, 256)        |       2332.508 (+-103.556)      |         840.194 (+-47.664)         |            935.625 (+-47.467)           |     1.114 (+-0.000)      |         2334.314 (+-91.644)
          Input (1, 3, 1200, 1300), torch.uint8, torch.contiguous_format | mode: nearest, align_corners: None, osize: (200, 300)    |        272.631 (+-11.348)       |         195.988 (+-5.748)          |            274.021 (+-9.475)            |     1.398 (+-0.000)      |          272.752 (+-12.716)
          Input (1, 3, 1200, 1300), torch.uint8, torch.channels_last | mode: nearest, align_corners: None, osize: (200, 300)        |        640.409 (+-25.465)       |         164.773 (+-7.372)          |            185.018 (+-8.349)            |     1.123 (+-0.000)      |          639.390 (+-30.761)
          Input (1, 3, 1200, 1300), torch.float32, torch.contiguous_format | mode: nearest, align_corners: None, osize: (200, 300)  |        158.602 (+-6.593)        |         220.478 (+-6.809)          |            286.376 (+-8.981)            |     1.299 (+-0.000)      |          158.557 (+-6.143)
          Input (1, 3, 1200, 1300), torch.float32, torch.channels_last | mode: nearest, align_corners: None, osize: (200, 300)      |        548.903 (+-22.889)       |         202.788 (+-9.158)          |            227.404 (+-8.995)            |     1.121 (+-0.000)      |          554.096 (+-21.330)
          Input (4, 3, 1200, 1300), torch.uint8, torch.contiguous_format | mode: nearest, align_corners: None, osize: (200, 300)    |       1036.061 (+-35.285)       |         680.728 (+-30.925)         |            986.254 (+-42.732)           |     1.449 (+-0.000)      |         1038.718 (+-43.070)
          Input (4, 3, 1200, 1300), torch.uint8, torch.channels_last | mode: nearest, align_corners: None, osize: (200, 300)        |       2504.520 (+-125.805)      |         550.067 (+-21.383)         |            628.000 (+-27.589)           |     1.142 (+-0.000)      |         2523.134 (+-113.336)
          Input (4, 3, 1200, 1300), torch.float32, torch.contiguous_format | mode: nearest, align_corners: None, osize: (200, 300)  |       1058.188 (+-57.853)       |        1216.427 (+-76.160)         |           1380.231 (+-98.939)           |     1.135 (+-0.000)      |         1057.031 (+-66.075)
          Input (4, 3, 1200, 1300), torch.float32, torch.channels_last | mode: nearest, align_corners: None, osize: (200, 300)      |       2305.911 (+-116.864)      |        1080.189 (+-79.934)         |           1141.561 (+-67.959)           |     1.057 (+-0.000)      |         2306.606 (+-121.544)
          Input (1, 3, 300, 400), torch.uint8, torch.contiguous_format | mode: nearest, align_corners: None, osize: (600, 700)      |       1689.489 (+-60.579)       |        1077.401 (+-44.948)         |           1634.264 (+-64.340)           |     1.517 (+-0.000)      |         1693.945 (+-67.998)
          Input (1, 3, 300, 400), torch.uint8, torch.channels_last | mode: nearest, align_corners: None, osize: (600, 700)          |       4198.368 (+-179.096)      |         886.656 (+-30.355)         |           1028.568 (+-46.310)           |     1.160 (+-0.000)      |         4174.351 (+-141.020)
          Input (1, 3, 300, 400), torch.float32, torch.contiguous_format | mode: nearest, align_corners: None, osize: (600, 700)    |        716.572 (+-51.954)       |        1175.864 (+-52.191)         |           1674.373 (+-51.815)           |     1.424 (+-0.000)      |          715.724 (+-41.104)
          Input (1, 3, 300, 400), torch.float32, torch.channels_last | mode: nearest, align_corners: None, osize: (600, 700)        |       3604.989 (+-132.489)      |        1096.933 (+-54.290)         |           1270.347 (+-60.932)           |     1.158 (+-0.000)      |         3601.864 (+-140.218)
          Input (4, 3, 300, 400), torch.uint8, torch.contiguous_format | mode: nearest, align_corners: None, osize: (600, 700)      |       6721.610 (+-355.997)      |        4203.213 (+-134.362)        |           6423.763 (+-225.311)          |     1.528 (+-0.000)      |         6715.626 (+-288.233)
          Input (4, 3, 300, 400), torch.uint8, torch.channels_last | mode: nearest, align_corners: None, osize: (600, 700)          |      16695.467 (+-709.620)      |        3460.013 (+-149.456)        |           4001.810 (+-218.093)          |     1.157 (+-0.000)      |        16621.138 (+-713.320)
          Input (4, 3, 300, 400), torch.float32, torch.contiguous_format | mode: nearest, align_corners: None, osize: (600, 700)    |       3020.017 (+-147.314)      |        4743.164 (+-135.850)        |           6709.494 (+-281.025)          |     1.415 (+-0.000)      |         3015.602 (+-105.852)
          Input (4, 3, 300, 400), torch.float32, torch.channels_last | mode: nearest, align_corners: None, osize: (600, 700)        |      14456.688 (+-752.839)      |        5150.893 (+-201.571)        |           5737.315 (+-138.011)          |     1.114 (+-0.000)      |        14464.472 (+-720.027)
    
    Times are in microseconds (us).
    ```
    
    This PR fixes arrange decomp such that `arange(s, dtype=torch.float32)` directly provides better IR and generated code.
    
    Code:
    ```python
    import torch
    
    def func(x):
        s = x.shape[-1]
        a = torch.arange(s, dtype=torch.float32)
        return s + a
    
    c_func = torch.compile(func)
    out = c_func(torch.rand(10))
    ```
    
    Graph on this PR:
    ```
     ===== Forward graph 0 =====
     /pytorch/torch/fx/_lazy_graph_module.py class <lambda>(torch.nn.Module):
        def forward(self):
            # File: check_arange_decomp.py:8 in func, code: a = torch.arange(s, dtype=torch.float32)
            iota: "i64[10]" = torch.ops.prims.iota.default(10, start = 0, step = 1, dtype = torch.int64, device = device(type='cpu'), requires_grad = False)
            convert_element_type: "f32[10]" = torch.ops.prims.convert_element_type.default(iota, torch.float32);  iota = None
    
            # File: check_arange_decomp.py:9 in func, code: return s + a
            add: "f32[10]" = torch.ops.aten.add.Tensor(convert_element_type, 10);  convert_element_type = None
            return (add,)
    ```
    and C++ on this PR:
    ```c++
    extern "C" void kernel(float* out_ptr0)
    {
        {
            #pragma GCC ivdep
            for(long x0=static_cast<long>(0L); x0<static_cast<long>(10L); x0+=static_cast<long>(1L))
            {
                auto tmp0 = c10::convert<long>(x0);
                auto tmp1 = c10::convert<float>(tmp0);
                auto tmp2 = static_cast<float>(10.0);
                auto tmp3 = decltype(tmp1)(tmp1 + tmp2);
                out_ptr0[static_cast<long>(x0)] = tmp3;
            }
        }
    }
    ```
    
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    vfdev-5 committed Apr 5, 2024
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