File size: 23,144 Bytes
be11144
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
/******************************************************************************
 * Copyright (c) 2011, Duane Merrill.  All rights reserved.
 * Copyright (c) 2011-2020, NVIDIA CORPORATION.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name of the NVIDIA CORPORATION nor the
 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL NVIDIA CORPORATION BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 ******************************************************************************/

/**
 * \file
 * Properties of a given CUDA device and the corresponding PTX bundle
 */

#pragma once

#include "util_type.cuh"
#include "util_arch.cuh"
#include "util_debug.cuh"
#include "util_cpp_dialect.cuh"
#include "util_namespace.cuh"
#include "util_macro.cuh"

#if CUB_CPP_DIALECT >= 2011 // C++11 and later.
#include <atomic>
#include <array>
#include <cassert>
#endif

/// Optional outer namespace(s)
CUB_NS_PREFIX

/// CUB namespace
namespace cub {


/**
 * \addtogroup UtilMgmt
 * @{
 */

#ifndef DOXYGEN_SHOULD_SKIP_THIS // Do not document


/**
 * \brief Alias temporaries to externally-allocated device storage (or simply return the amount of storage needed).
 */
template <int ALLOCATIONS>
__host__ __device__ __forceinline__
cudaError_t AliasTemporaries(
    void    *d_temp_storage,                    ///< [in] %Device-accessible allocation of temporary storage.  When NULL, the required allocation size is written to \p temp_storage_bytes and no work is done.
    size_t& temp_storage_bytes,                ///< [in,out] Size in bytes of \t d_temp_storage allocation
    void*   (&allocations)[ALLOCATIONS],        ///< [in,out] Pointers to device allocations needed
    size_t  (&allocation_sizes)[ALLOCATIONS])   ///< [in] Sizes in bytes of device allocations needed
{
    const int ALIGN_BYTES   = 256;
    const int ALIGN_MASK    = ~(ALIGN_BYTES - 1);

    // Compute exclusive prefix sum over allocation requests
    size_t allocation_offsets[ALLOCATIONS];
    size_t bytes_needed = 0;
    for (int i = 0; i < ALLOCATIONS; ++i)
    {
        size_t allocation_bytes = (allocation_sizes[i] + ALIGN_BYTES - 1) & ALIGN_MASK;
        allocation_offsets[i] = bytes_needed;
        bytes_needed += allocation_bytes;
    }
    bytes_needed += ALIGN_BYTES - 1;

    // Check if the caller is simply requesting the size of the storage allocation
    if (!d_temp_storage)
    {
        temp_storage_bytes = bytes_needed;
        return cudaSuccess;
    }

    // Check if enough storage provided
    if (temp_storage_bytes < bytes_needed)
    {
        return CubDebug(cudaErrorInvalidValue);
    }

    // Alias
    d_temp_storage = (void *) ((size_t(d_temp_storage) + ALIGN_BYTES - 1) & ALIGN_MASK);
    for (int i = 0; i < ALLOCATIONS; ++i)
    {
        allocations[i] = static_cast<char*>(d_temp_storage) + allocation_offsets[i];
    }

    return cudaSuccess;
}


/**
 * \brief Empty kernel for querying PTX manifest metadata (e.g., version) for the current device
 */
template <typename T>
__global__ void EmptyKernel(void) { }

#endif  // DOXYGEN_SHOULD_SKIP_THIS

/**
 * \brief Returns the current device or -1 if an error occurred.
 */
CUB_RUNTIME_FUNCTION __forceinline__ int CurrentDevice()
{
#if defined(CUB_RUNTIME_ENABLED) // Host code or device code with the CUDA runtime.

    int device = -1;
    if (CubDebug(cudaGetDevice(&device))) return -1;
    return device;

#else // Device code without the CUDA runtime.

    return -1;

#endif
}

/**
 * \brief RAII helper which saves the current device and switches to the
 *        specified device on construction and switches to the saved device on
 *        destruction.
 */
struct SwitchDevice
{
private:
    int const old_device;
    bool const needs_reset;
public:
    __host__ __forceinline__ SwitchDevice(int new_device)
      : old_device(CurrentDevice()), needs_reset(old_device != new_device)
    {
        if (needs_reset)
            CubDebug(cudaSetDevice(new_device));
    }

    __host__ __forceinline__ ~SwitchDevice()
    {
        if (needs_reset)
            CubDebug(cudaSetDevice(old_device));
    }
};

/**
 * \brief Returns the number of CUDA devices available or -1 if an error
 *        occurred.
 */
CUB_RUNTIME_FUNCTION __forceinline__ int DeviceCountUncached()
{
#if defined(CUB_RUNTIME_ENABLED) // Host code or device code with the CUDA runtime.

    int count = -1;
    if (CubDebug(cudaGetDeviceCount(&count)))
        // CUDA makes no guarantees about the state of the output parameter if
        // `cudaGetDeviceCount` fails; in practice, they don't, but out of
        // paranoia we'll reset `count` to `-1`.
        count = -1;
    return count;

#else // Device code without the CUDA runtime.

    return -1;

#endif
}

#if CUB_CPP_DIALECT >= 2011 // C++11 and later.

/**
 * \brief Cache for an arbitrary value produced by a nullary function.
 */
template <typename T, T(*Function)()>
struct ValueCache
{
    T const value;

    /**
     * \brief Call the nullary function to produce the value and construct the
     *        cache.
     */
    __host__ __forceinline__ ValueCache() : value(Function()) {}
};

#endif

#if CUB_CPP_DIALECT >= 2011
// Host code, only safely usable in C++11 or newer, where thread-safe
// initialization of static locals is guaranteed.  This is a separate function
// to avoid defining a local static in a host/device function.
__host__ __forceinline__ int DeviceCountCachedValue()
{
    static ValueCache<int, DeviceCountUncached> cache;
    return cache.value;
}
#endif

/**
 * \brief Returns the number of CUDA devices available.
 *
 * \note This function may cache the result internally.
 *
 * \note This function is thread safe.
 */
CUB_RUNTIME_FUNCTION __forceinline__ int DeviceCount()
{
    int result = -1;
    if (CUB_IS_HOST_CODE) {
        #if CUB_INCLUDE_HOST_CODE
            #if CUB_CPP_DIALECT >= 2011
                // Host code and C++11.
                result = DeviceCountCachedValue();
            #else
                // Host code and C++98.
                result = DeviceCountUncached();
            #endif
        #endif
    } else {
        #if CUB_INCLUDE_DEVICE_CODE
            // Device code.
            result = DeviceCountUncached();
        #endif
    }
    return result;
}

#if CUB_CPP_DIALECT >= 2011 // C++11 and later.

/**
 * \brief Per-device cache for a CUDA attribute value; the attribute is queried
 *        and stored for each device upon construction.
 */
struct PerDeviceAttributeCache
{
    struct DevicePayload
    {
        int         attribute;
        cudaError_t error;
    };

    // Each entry starts in the `DeviceEntryEmpty` state, then proceeds to the
    // `DeviceEntryInitializing` state, and then proceeds to the
    // `DeviceEntryReady` state. These are the only state transitions allowed;
    // e.g. a linear sequence of transitions.
    enum DeviceEntryStatus
    {
        DeviceEntryEmpty = 0,
        DeviceEntryInitializing,
        DeviceEntryReady
    };

    struct DeviceEntry
    {
        std::atomic<DeviceEntryStatus> flag;
        DevicePayload                  payload;
    };

private:
    std::array<DeviceEntry, CUB_MAX_DEVICES> entries_;

public:
    /**
     * \brief Construct the cache.
     */
    __host__ __forceinline__ PerDeviceAttributeCache() : entries_()
    {
        assert(DeviceCount() <= CUB_MAX_DEVICES);
    }

    /**
     * \brief Retrieves the payload of the cached function \p f for \p device.
     *
     * \note You must pass a morally equivalent function in to every call or
     *       this function has undefined behavior.
     */
    template <typename Invocable>
    __host__ DevicePayload operator()(Invocable&& f, int device)
    {
        if (device >= DeviceCount())
            return DevicePayload{0, cudaErrorInvalidDevice};

        auto& entry   = entries_[device];
        auto& flag    = entry.flag;
        auto& payload = entry.payload;

        DeviceEntryStatus old_status = DeviceEntryEmpty;

        // First, check for the common case of the entry being ready.
        if (flag.load(std::memory_order_acquire) != DeviceEntryReady)
        {
            // Assume the entry is empty and attempt to lock it so we can fill
            // it by trying to set the state from `DeviceEntryReady` to
            // `DeviceEntryInitializing`.
            if (flag.compare_exchange_strong(old_status, DeviceEntryInitializing,
                                             std::memory_order_acq_rel,
                                             std::memory_order_acquire))
            {
                // We successfully set the state to `DeviceEntryInitializing`;
                // we have the lock and it's our job to initialize this entry
                // and then release it.

                // We don't use `CubDebug` here because we let the user code
                // decide whether or not errors are hard errors.
                if (payload.error = std::forward<Invocable>(f)(payload.attribute))
                    // Clear the global CUDA error state which may have been
                    // set by the last call. Otherwise, errors may "leak" to
                    // unrelated kernel launches.
                    cudaGetLastError();

                // Release the lock by setting the state to `DeviceEntryReady`.
                flag.store(DeviceEntryReady, std::memory_order_release);
            }

            // If the `compare_exchange_weak` failed, then `old_status` has
            // been updated with the value of `flag` that it observed.

            else if (old_status == DeviceEntryInitializing)
            {
                // Another execution agent is initializing this entry; we need
                // to wait for them to finish; we'll know they're done when we
                // observe the entry status as `DeviceEntryReady`.
                do { old_status = flag.load(std::memory_order_acquire); }
                while (old_status != DeviceEntryReady);
                // FIXME: Use `atomic::wait` instead when we have access to
                // host-side C++20 atomics. We could use libcu++, but it only
                // supports atomics for SM60 and up, even if you're only using
                // them in host code.
            }
        }

        // We now know that the state of our entry is `DeviceEntryReady`, so
        // just return the entry's payload.
        return entry.payload;
    }
};

#endif

/**
 * \brief Retrieves the PTX version that will be used on the current device (major * 100 + minor * 10).
 */
CUB_RUNTIME_FUNCTION __forceinline__ cudaError_t PtxVersionUncached(int& ptx_version)
{
    // Instantiate `EmptyKernel<void>` in both host and device code to ensure
    // it can be called.
    typedef void (*EmptyKernelPtr)();
    EmptyKernelPtr empty_kernel = EmptyKernel<void>;

    // This is necessary for unused variable warnings in host compilers. The
    // usual syntax of (void)empty_kernel; was not sufficient on MSVC2015.
    (void)reinterpret_cast<void*>(empty_kernel);

    cudaError_t result = cudaSuccess;
    if (CUB_IS_HOST_CODE) {
       #if CUB_INCLUDE_HOST_CODE
            cudaFuncAttributes empty_kernel_attrs;

            do {
                if (CubDebug(result = cudaFuncGetAttributes(&empty_kernel_attrs, empty_kernel)))
                    break;
            }
            while(0);

            ptx_version = empty_kernel_attrs.ptxVersion * 10;
        #endif
    } else {
        #if CUB_INCLUDE_DEVICE_CODE
            // This is necessary to ensure instantiation of EmptyKernel in device code.
            // The `reinterpret_cast` is necessary to suppress a set-but-unused warnings.
            // This is a meme now: https://twitter.com/blelbach/status/1222391615576100864
            (void)reinterpret_cast<EmptyKernelPtr>(empty_kernel);

            ptx_version = CUB_PTX_ARCH;
        #endif
    }
    return result;
}

/**
 * \brief Retrieves the PTX version that will be used on \p device (major * 100 + minor * 10).
 */
__host__ __forceinline__ cudaError_t PtxVersionUncached(int& ptx_version, int device)
{
    SwitchDevice sd(device);
    return PtxVersionUncached(ptx_version);
}

#if CUB_CPP_DIALECT >= 2011 // C++11 and later.
template <typename Tag>
__host__ __forceinline__ PerDeviceAttributeCache& GetPerDeviceAttributeCache()
{
    // C++11 guarantees that initialization of static locals is thread safe.
    static PerDeviceAttributeCache cache;
    return cache;
}

struct PtxVersionCacheTag {};
struct SmVersionCacheTag {};
#endif

/**
 * \brief Retrieves the PTX version that will be used on \p device (major * 100 + minor * 10).
 *
 * \note This function may cache the result internally.
 *
 * \note This function is thread safe.
 */
__host__ __forceinline__ cudaError_t PtxVersion(int& ptx_version, int device)
{
#if CUB_CPP_DIALECT >= 2011 // C++11 and later.

    auto const payload = GetPerDeviceAttributeCache<PtxVersionCacheTag>()(
      // If this call fails, then we get the error code back in the payload,
      // which we check with `CubDebug` below.
      [=] (int& pv) { return PtxVersionUncached(pv, device); },
      device);

    if (!CubDebug(payload.error))
        ptx_version = payload.attribute;

    return payload.error;

#else // Pre C++11.

    return PtxVersionUncached(ptx_version, device);

#endif
}

/**
 * \brief Retrieves the PTX version that will be used on the current device (major * 100 + minor * 10).
 *
 * \note This function may cache the result internally.
 *
 * \note This function is thread safe.
 */
CUB_RUNTIME_FUNCTION __forceinline__ cudaError_t PtxVersion(int& ptx_version)
{
    cudaError_t result = cudaErrorUnknown;
    if (CUB_IS_HOST_CODE) {
        #if CUB_INCLUDE_HOST_CODE
            #if CUB_CPP_DIALECT >= 2011
                // Host code and C++11.
                auto const device = CurrentDevice();

                auto const payload = GetPerDeviceAttributeCache<PtxVersionCacheTag>()(
                  // If this call fails, then we get the error code back in the payload,
                  // which we check with `CubDebug` below.
                  [=] (int& pv) { return PtxVersionUncached(pv, device); },
                  device);

                if (!CubDebug(payload.error))
                    ptx_version = payload.attribute;

                result = payload.error;
            #else
                // Host code and C++98.
                result = PtxVersionUncached(ptx_version);
            #endif
        #endif
    } else {
        #if CUB_INCLUDE_DEVICE_CODE
            // Device code.
            result = PtxVersionUncached(ptx_version);
        #endif
    }
    return result;
}

/**
 * \brief Retrieves the SM version of \p device (major * 100 + minor * 10)
 */
CUB_RUNTIME_FUNCTION __forceinline__ cudaError_t SmVersionUncached(int& sm_version, int device = CurrentDevice())
{
#if defined(CUB_RUNTIME_ENABLED) // Host code or device code with the CUDA runtime.

    cudaError_t error = cudaSuccess;
    do
    {
        int major = 0, minor = 0;
        if (CubDebug(error = cudaDeviceGetAttribute(&major, cudaDevAttrComputeCapabilityMajor, device))) break;
        if (CubDebug(error = cudaDeviceGetAttribute(&minor, cudaDevAttrComputeCapabilityMinor, device))) break;
        sm_version = major * 100 + minor * 10;
    }
    while (0);

    return error;

#else // Device code without the CUDA runtime.

    (void)sm_version;
    (void)device;

    // CUDA API calls are not supported from this device.
    return CubDebug(cudaErrorInvalidConfiguration);

#endif
}

/**
 * \brief Retrieves the SM version of \p device (major * 100 + minor * 10)
 *
 * \note This function may cache the result internally.
 *
 * \note This function is thread safe.
 */
CUB_RUNTIME_FUNCTION __forceinline__ cudaError_t SmVersion(int& sm_version, int device = CurrentDevice())
{
    cudaError_t result = cudaErrorUnknown;
    if (CUB_IS_HOST_CODE) {
        #if CUB_INCLUDE_HOST_CODE
            #if CUB_CPP_DIALECT >= 2011
                // Host code and C++11
                auto const payload = GetPerDeviceAttributeCache<SmVersionCacheTag>()(
                  // If this call fails, then we get the error code back in the payload,
                  // which we check with `CubDebug` below.
                  [=] (int& pv) { return SmVersionUncached(pv, device); },
                  device);

                if (!CubDebug(payload.error))
                    sm_version = payload.attribute;

                result = payload.error;
            #else
                // Host code and C++98
                result = SmVersionUncached(sm_version, device);
            #endif
        #endif
    } else {
        #if CUB_INCLUDE_DEVICE_CODE
            result = SmVersionUncached(sm_version, device);
        #endif
    }
    return result;
}

/**
 * Synchronize the specified \p stream.
 */
CUB_RUNTIME_FUNCTION __forceinline__ cudaError_t SyncStream(cudaStream_t stream)
{
    cudaError_t result = cudaErrorUnknown;
    if (CUB_IS_HOST_CODE) {
        #if CUB_INCLUDE_HOST_CODE
            result = CubDebug(cudaStreamSynchronize(stream));
        #endif
    } else {
        #if CUB_INCLUDE_DEVICE_CODE
            #if defined(CUB_RUNTIME_ENABLED) // Device code with the CUDA runtime.
                (void)stream;
                // Device can't yet sync on a specific stream
                result = CubDebug(cudaDeviceSynchronize());
            #else // Device code without the CUDA runtime.
                (void)stream;
                // CUDA API calls are not supported from this device.
                result = CubDebug(cudaErrorInvalidConfiguration);
            #endif
        #endif
    }
    return result;
}


/**
 * \brief Computes maximum SM occupancy in thread blocks for executing the given kernel function pointer \p kernel_ptr on the current device with \p block_threads per thread block.
 *
 * \par Snippet
 * The code snippet below illustrates the use of the MaxSmOccupancy function.
 * \par
 * \code
 * #include <cub/cub.cuh>   // or equivalently <cub/util_device.cuh>
 *
 * template <typename T>
 * __global__ void ExampleKernel()
 * {
 *     // Allocate shared memory for BlockScan
 *     __shared__ volatile T buffer[4096];
 *
 *        ...
 * }
 *
 *     ...
 *
 * // Determine SM occupancy for ExampleKernel specialized for unsigned char
 * int max_sm_occupancy;
 * MaxSmOccupancy(max_sm_occupancy, ExampleKernel<unsigned char>, 64);
 *
 * // max_sm_occupancy  <-- 4 on SM10
 * // max_sm_occupancy  <-- 8 on SM20
 * // max_sm_occupancy  <-- 12 on SM35
 *
 * \endcode
 *
 */
template <typename KernelPtr>
CUB_RUNTIME_FUNCTION __forceinline__
cudaError_t MaxSmOccupancy(
    int&                max_sm_occupancy,          ///< [out] maximum number of thread blocks that can reside on a single SM
    KernelPtr           kernel_ptr,                 ///< [in] Kernel pointer for which to compute SM occupancy
    int                 block_threads,              ///< [in] Number of threads per thread block
    int                 dynamic_smem_bytes = 0)
{
#ifndef CUB_RUNTIME_ENABLED

    (void)dynamic_smem_bytes;
    (void)block_threads;
    (void)kernel_ptr;
    (void)max_sm_occupancy;

    // CUDA API calls not supported from this device
    return CubDebug(cudaErrorInvalidConfiguration);

#else

    return CubDebug(cudaOccupancyMaxActiveBlocksPerMultiprocessor(
        &max_sm_occupancy,
        kernel_ptr,
        block_threads,
        dynamic_smem_bytes));

#endif  // CUB_RUNTIME_ENABLED
}


/******************************************************************************
 * Policy management
 ******************************************************************************/

/**
 * Kernel dispatch configuration
 */
struct KernelConfig
{
    int block_threads;
    int items_per_thread;
    int tile_size;
    int sm_occupancy;

    CUB_RUNTIME_FUNCTION __forceinline__
    KernelConfig() : block_threads(0), items_per_thread(0), tile_size(0), sm_occupancy(0) {}

    template <typename AgentPolicyT, typename KernelPtrT>
    CUB_RUNTIME_FUNCTION __forceinline__
    cudaError_t Init(KernelPtrT kernel_ptr)
    {
        block_threads        = AgentPolicyT::BLOCK_THREADS;
        items_per_thread     = AgentPolicyT::ITEMS_PER_THREAD;
        tile_size            = block_threads * items_per_thread;
        cudaError_t retval   = MaxSmOccupancy(sm_occupancy, kernel_ptr, block_threads);
        return retval;
    }
};



/// Helper for dispatching into a policy chain
template <int PTX_VERSION, typename PolicyT, typename PrevPolicyT>
struct ChainedPolicy
{
   /// The policy for the active compiler pass
   typedef typename If<(CUB_PTX_ARCH < PTX_VERSION), typename PrevPolicyT::ActivePolicy, PolicyT>::Type ActivePolicy;

   /// Specializes and dispatches op in accordance to the first policy in the chain of adequate PTX version
   template <typename FunctorT>
   CUB_RUNTIME_FUNCTION __forceinline__
   static cudaError_t Invoke(int ptx_version, FunctorT& op)
   {
       if (ptx_version < PTX_VERSION) {
           return PrevPolicyT::Invoke(ptx_version, op);
       }
       return op.template Invoke<PolicyT>();
   }
};

/// Helper for dispatching into a policy chain (end-of-chain specialization)
template <int PTX_VERSION, typename PolicyT>
struct ChainedPolicy<PTX_VERSION, PolicyT, PolicyT>
{
    /// The policy for the active compiler pass
    typedef PolicyT ActivePolicy;

    /// Specializes and dispatches op in accordance to the first policy in the chain of adequate PTX version
    template <typename FunctorT>
    CUB_RUNTIME_FUNCTION __forceinline__
    static cudaError_t Invoke(int /*ptx_version*/, FunctorT& op) {
        return op.template Invoke<PolicyT>();
    }
};




/** @} */       // end group UtilMgmt

}               // CUB namespace
CUB_NS_POSTFIX  // Optional outer namespace(s)