mkl_free_buffers

Developer Reference for Intel® oneAPI Math Kernel Library for C

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ID 766684

Date 4/28/2026

Version

Public

mkl_free_buffers

Frees unused memory allocated by Intel® oneAPI Math Kernel Library (oneMKL) on the Host, including both CPU- and GPU-related buffers.

Syntax

voidmkl_free_buffers ( void );

Include Files

mkl.h

Description

To improve performance of Intel® oneAPI Math Kernel Library (oneMKL) on CPU, the Memory Allocator uses per-thread memory pools where buffers may be collected for fast reuse. Intel® oneAPI Math Kernel Library (oneMKL) also allocates temporary buffers on the host memory to improve performance of GPU kernels. The mkl_free_buffers function frees both types of memory.

See the Intel® oneAPI Math Kernel Library (oneMKL) Developer Guide Linux or Windows for details.

You should call mkl_free_buffers after the last call to Intel® oneAPI Math Kernel Library (oneMKL) functions. In large applications, if you suspect that the memory may get insufficient, you may call this function earlier, but anticipate a drop in performance that may occur due to reallocation of buffers for subsequent calls to Intel® oneAPI Math Kernel Library (oneMKL) functions.

NOTE:

mkl_free_buffers is triggered automatically during oneMKL unloading when it is possible as part of mkl_finalize ; however, in the case of statically linked oneMKL, the user must call mkl_free_buffers or mkl_finalize manually in order to clean up oneMKL internal buffers when oneMKL is no longer needed.

Product and Performance Information Performance varies by use, configuration and other factors. Learn more at www.Intel.com/PerformanceIndex . Notice revision #20201201

Usage of mkl_free_buffers with FFT Functions (C Example)

DFTI_DESCRIPTOR_HANDLE hand1;
DFTI_DESCRIPTOR_HANDLE hand2;
void mkl_free_buffers(void);
. . . . . .
/* Using Intel MKL FFT */
Status = DftiCreateDescriptor(&hand1, DFTI_SINGLE, DFTI_COMPLEX, dim, m1);
Status = DftiCommitDescriptor(hand1);
Status = DftiComputeForward(hand1, s_array1);
. . . . . .
Status = DftiCreateDescriptor(&hand2, DFTI_SINGLE, DFTI_COMPLEX, dim, m2);
Status = DftiCommitDescriptor(hand2);
. . . . . .
Status = DftiFreeDescriptor(&hand1);
. . . . . .
Status = DftiComputeBackward(hand2, s_array2));
Status = DftiFreeDescriptor(&hand2);
/* Here you finish using Intel MKL FFT */
/* Memory leak will be triggered by any memory control tool */
/* Use mkl_free_buffers() to avoid memory leaking */
mkl_free_buffers();

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Developer Reference for Intel® oneAPI Math Kernel Library for C

mkl_free_buffers

Syntax

Include Files

Description